please vote on the poll if you would like to see the transmitter support!!!
the evos Broadcom chip has a built in fm receiver and also a transmitter.
according to some threads and diagrams ive seen the transmitter does have a power source, it just doesnt have and software code to actually work.
like hdmi the hardware was there but there was no code set up, therefore we didnt have full hdmi out. it had to be built from scratch.
the hardware for the fm transmitter is there we just need some one to build the code for it.
some one please take this on!!
This tutorial was originally posted in > android development and hacking > android software development.
i am reposting it here in the evo forums for guidelines
its a nice tutorial but its old. i think it was for android 2.0 ive followed the tutorial but i couldnt get it working, and i by no means have the experience to switch things up and get it working.
[TUTORIAL] Reverse engineering HTC FM Radio for noobs (on EVO 4G)
Okay, I'm writing this because I want to help any other newbies trying to learn how to reverse engineer. The technical details involved in this are extremely daunting, so the purpose of this tutorial is to first explain in layman terms exactly what you're trying to accomplish and what to expect. Then we'll go over the details. That way you're not completely blind going into this. I'm fairly new to the scene, so I'm not as knowledgeable as everyone else. If you see any errors in my post, let me know so I can change. I'm going to assume you know a little bit of Java, can find your way around a computer, and know nothing about Android. The techniques used should work with other Android phones. For this tutorial I'm using Windows 7, Cygwin, and my stock (not rooted) EVO 4G mobile phone.
The FM tuner for the Evo is run by a Broadcom chip: BCM4329. This chip is pretty amazing in that it does wireless, bluetooth, and it has an FM receiver/transmitter. We're interested in the FM receiver / transmitter.
Now, all android phones are based on a Linux kernel. Basically they're Linux running computers. The Android operating system is then installed onto the linux system. Every app is then run off of Android.
Android is based on Java but it is not a Java system. It uses a virtual machine called Dalvik. Google did this to get around licensing issues with Sun Microsystems. So they pretty much invented their own machine language (called byte code) for the Java language. This makes things complicated for the reverse engineer because from what I've read, once Java is converted into this machine language or byte code, it can't be converted back.
So let's rehash.
If you were programming strictly in Java, you would see these extensions:
Java source code = .java
Compiled Java source code = Java byte code = .class
Compressed file to package your program = .jar (Java Archive)
But since you're programming in Android and Dalvik, you will see these:
Java source code = .java
Compiled Java source code = Dalvik byte code = .dex
Compressed file to package your program = .apk
(I haven't mentioned this, but HTC further Optimizes their .dex code)
Optimized Dalvik byte code = .odex
I'm writing all of these down because it's very easy to get confused with all of the extensions. (for me at least!). remember how I said once you go dex, you can't go back to java? That's where JesusFreke comes in. He's a senior member of XDA, and he created "baksmali" and "smali", two programs that can convert the Dalvik code back into a human readable format. These files have extensions of .smali
Decompiled Dalvik byte code = .smali
But what can you do with .smali files? That's where this other senior member, brut.all comes in: He developed apktool. apktool takes JesusFreke's work to the next level. This program in conjunction with NetBeans, actually lets you trace through any program using the .smali code taken from JesusFreke's programs!
apktool does this by converting those .smali files into "fake" .java files that can be used by the NetBeans (program that compiles and makes java programs) IDE. I say "fake" because apktool embeds the .smali code into java files as comments. However, once you attach a debugger to NetBeans, you'll see that the debugger will follow line by line every execution statement found in the smali code!
So...... you can take the program you want, plug it into Net Beans using a debugger (using the default ddms command provided by Android SDK), and you can trace everything you do in the program. I have it connected to my phone, so whenever I push a button while running my HTC FMRadio app or unplug my headphones,I see the corresponding response to the HTCFMRadio code I have loaded in NetBeans. I can now see in real-time how the program operates from my own interactions... JAM.
Technical Aspects: How to get from ground zero to tracing HTCFMRadio?
1.) Download Android SDK - Go to google development site and follow instructions: Make sure to download the latest Java JDK. Once that is installed, download NetBeans 6.8. Unfortunately, smali debugging does not work with the lastest versions of NetBeans.
Download the "Java SE" version for minimal space
http://netbeans.org/downloads/6.8/index.html
You can follow the rest of Google walkthrough and download Eclipse and ADT plugin, but it's not pertinent to this. You're going to be using adb and ddms from the android SDK extensively, so make sure the path for </android SDK/tools> is included in the PATH variable in your ENVIRONMENT SETTINGS. To get here, right click My computer, click properties, Advanced Settings, ENVIRONMENT SETTINGS.
2.) Search for 7z and download it. It is an awesome and free compression tool that will be extremely useful. It can be used to "unzip" .jar, .apk, and other compressed formats.
3.) Get the Radio app. You can do this by going to "shipped-roms" website, downloading the latest Supersonic image, and following the directions in the unlockr tutorial for HTC kitchens at the unlockr website... (once you have extracted the files from the image, you can look in the system/app and system/framework directories to get the files listed below) or:
you can pull the following files from your phone:
Using the command prompt type (and with phone plugged in, and with USB debugging enabled on phone):
adb pull /system/app/HtcFMRadio.odex
adb pull /system/app/HtcFMRadio.apk
adb pull /system/framework ./framework
This will put HtcFMRadio.odex and HtcFMRadio.apk in the current directory and create a framework directory with more files. A couple of the files in the framework are needed for the HtcFMRadio app, but for simplicity, we're just going to pull the whole directory.
Now that we have the files, we have to make a few changes to make the app installable and to be viewable by the debugger. To do this we have to decompile the .odex format into a human readable format we can edit. That brings us to:
3.) Download baksmali and smali from Project Hosting on Google Code (google search smali).
Usually an Android application is made up of one file, an apk file. Inside the apk file is an AndroidManifest.xml file, a classes.dex file (compiled Java code for the program), and other folders. The other folders contain either graphics or other .xml files that tell the program how it should look to the user. We don't have to worry about those for now. This is important because APKTOOL only opens programs set up this way. But wait up? We didn't download one .apk file, we downloaded an .apk file and an .odex file! What gives? Well, if you right click the apk file and open it (using 7z), you'll see that it's missing the classes.dex file. The dex file for the app is actually the HtcFMRadio.odex file we downloaded. So, to make this system app more like a nominal app, we have to find a way to convert the HtcFMRadio.odex to a classes.dex file. That's easy with baksmali and smali!
Once you download goto command prompt and type:
java -jar baksmali-<version>.jar -d framework -x HtcFMRadio.odex
(Remember to match baksmali-<version>.jar with the filename of baksmali you downloaded)
If done correctly, you should see a newly created \out directory
This creates an out\com\htc\fm directory with many .smali files.
Now let's reverse the process and put it back as a dex file. Type at command prompt:
java -jar smali-<version>.jar out -o classes.dex
If done correctly you'll see a newly created classes.dex.
now, right click on HtcFMRadio.apk (select 7z and open). Drag classes.dex into the file. Say yes to the prompt. Now you have a normal apk file APKTOOL can read!
4.) Download APKTOOL from Project Hosting on Google Code and the helper apps for your OS. (If you're extracting files for windows OS you should have apktool.bat and aapt.exe). Extract (again using 7z, don't you love this program?) apktool.jar (keep it as a jar file, don't extract the stuff inside of it), apktool.bat, and aapt.exe to the directory you're working on. To make things neat, you can also delete HtcFMRadio.odex (you don't need it anymore) and classes.dex (make sure you put it in the HtcFMRadio.apk file first!)
If this is the first time you're using apktool, then you have to install the htc framework so apktool can baksmali the Radio app. You only have to do this once:
apktool if ./framework/com.htc.resources.apk
Alright, at the command prompt:
apktool d -d HtcFMRadio.apk
This extracts the contents of HtcFMRadio.apk and places them in the HtcFMRadio directory. However, there are two major differences between this content and the content created in step 3. If you go into the smali directory you'll see that instead of .smali files, you'll see .java files. And if you go back and edit the AndroidManifest.xml file, you will also see that it's in text! Android applications convert their xml files to binary format. Now that APKTOOL has converted everything to an IDE friendly format, we can use NetBeans to edit everything. The first thing we're going to do is edit AndroidManifest.xml (using notepad) and add the following:
android:debuggable="true" to the Application tag.
IT should now look like this:
<application android:theme="@android:style/Theme.Black.NoTitleBar" android:label="@string/fm_app_name" android:icon="@drawable/fm_radio" android:taskAffinity="android.task.fmradio" android:description="@string/htc_corp" android:allowTaskReparenting="true" android:debuggable="true">
This permission lets the debugger watch the program while it's running on the phone.
We are going to run into two problems if we try to install this program. One is that Android doesn't let you install more than one copy of a system app. The second issue is that if we change the signature of our system app, then we'll have to change the signatures of our other system apps as well! Ahh.... So, to get around that, we're going to trick Android into thinking we have a completely new program. We're going to do that by renaming the com.htc.fm class to com.htc.modradio class. Next step:
5.) Cygwin (or Linux virtual machine)
The easiest way that I can think of to replace strings in multiple files is by using linux. You can most definitely do it in WIndows, but I dont know how. If you let me know how, I can put it in this tutorial.
(update: you can use Notepad++ to easily find/replace strings in multiple files for Windows. You still, however, want to download Cygwin if you're going to develop with Android-NDK.)
For now, just search for Cygwin (Cygwin is a program that lets you run Linux commands from a command prompt using your Windows directories), and install it. Make sure to have the Perl option selected. You'll need Perl to make the following commands work.
Once you get Cygwin up and running
cd <to your HtcFMRadio directory>
in my case it's
cd /cygdrive/c/Users/Jerry/Desktop/HtcFMRadio
now type the following commands in this order:
this command changes all occurances of htc/fm to htc/modradio in your xml and .java files.
find ./ -type f | xargs perl -pi -e 's/htc\/fm/htc\/modradio/g'
this command changes all occurances of htc.fm to htc.modradio
find ./ -type f | xargs perl -pi -e 's/htc.fm/htc.modradio/g'
If you don't follow this order, your source code will get messed up.
If using cygwin, a bunch of .bak files will be created. Using windows search, find all .bak files in your HtcFMRadio directory, then select them all and delete them (Make sure they are only files with .bak!)
Now just rename the fm directory to modradio. It is located in HtcFMRadio/smali/com/htc
Now go to your windows command prompt and type:
apktool b -d .\HtcFMRadio modradio.apk
Now sign and install modradio.apk on your phone.
adb install modradio.apk
If you have never signed before, then you need to use keytool and jarsigner. These two files are in your JDK directory, so make sure you include your JDK directory in the PATH variable of your ENVIRONMENT SETTINGS. (To get here, right click on My Computer, click Properties, Advanced Settings, Environment Variables. Once you make change, open up a new COMMAND prompt to see changes).
cd to the directory which has modradio.apk
now type:
keytool -genkeypair
Answer all questions, then use the same password for all password prompts.
Next type:
jarsigner -verbose modradio.apk mykey
Type in the password you created in the above step. Your apk should now be signed.
Next install:
adb install modradio.apk
Success!
6.) Testing the app on phone
Go to your phone and you'll now see a new FMRadio icon next to your first. Click on it and watch it open. It should now be able to play music. Keep it open.
7.) Using Netbeans
Go into HtcFMRadio and delete the build directory created by APKTOOL.
Now open up Net Beans and click on File, New Project, Select Java Project with Existing Sources, click on Next
Select HtcFMRadio directory for Project Folder, rename Project Name to whatever you want. Let's type in ModRadio. click on Next
Next to "Source Package Folders" click on "Add Folder" and select the smali directory.
Click Finish. For a quick tutorial by Brut.all, search APKTOOL in youtube and click on: Apktool Demo 2 - Smali improvements
Right click on Libraries. Click on "Add Jar / Folder". You want to add Android.Jar. Since I have Android 2.1 loaded I went to /platforms/android-7 located in my android SDK directory.
Your project is now ready for editting!
8.) Running the Debugger to trace through program.
Next go back to Windows command prompt and type ddms. This runs the Dalvik Debug Monitor. A window should open up. In the left hand side you should see com.htc.modradio. That's our app! To the right you're going to see 2 numbers, you're interested in the one to the right, 4 cells away from com.htc.modradio. This number is a port number, and you're going to use it to communicate with NetBeans. (In my case it is 8603)
Go back to NetBeans and click on Debug, Attach Debugger.
In the host field type: localhost
In the Port field: type in the second number you saw. (8603)
If everything is working you'll see a bug appear next to com.htc.modradio in the Dalvik Debug Monitor. Look at the bottom bar of NetBeans for feedback. If you get errors make sure the numbers match, or try port 8700 and make sure you select com.htc.modradio in the Dalvik Debug Monitor. Port 8700 is the default port used for whatever program you select in Dalvik Debug Monitor.
9.) Setting a breakpoint
I'm making this a seperate step because it is completely arbitrary. When creating a break point be sure to follow this rule:
You must select line with some instruction, you can't set breakpoint on lines starting with ".", ":" or "#".
Rather than looking for a spot to breakpoint, though, I'll tell you where to put one so you can quickly see how the debugger traces through the code. You aren't "REQUIRED" to do the next step, but if you want to trace you have to put a breakpoint somewhere.
In Net Beans click on the Project tab, click on Source Packages, com.htc.modradio, and then doubleclick on BroadcomFMTuner.java
We're going to insert a breakpoint. Scroll down to line 3226 and on your keyboard press: CTRL-SHIFT-F8, select line in dropdown box and hit ok. (To keep it simple, I usually look for "invoke" instructions to set breakpoints at)
Now go to your phone and click on the physical "back" button on your phone. This will clear the radio,(you should still be able to listen to music). Drag your status bar down. You should see a radio icon. Click on it again. The radio backgroudn will appear, but you wont' see any text or anything. Now go back to your netbeans application. You should now see debug options highlighted! Click on Step Over (F8) to step through!
{
"lightbox_close": "Close",
"lightbox_next": "Next",
"lightbox_previous": "Previous",
"lightbox_error": "The requested content cannot be loaded. Please try again later.",
"lightbox_start_slideshow": "Start slideshow",
"lightbox_stop_slideshow": "Stop slideshow",
"lightbox_full_screen": "Full screen",
"lightbox_thumbnails": "Thumbnails",
"lightbox_download": "Download",
"lightbox_share": "Share",
"lightbox_zoom": "Zoom",
"lightbox_new_window": "New window",
"lightbox_toggle_sidebar": "Toggle sidebar"
}
i found a few things.
http://pdf.eccn.com/pdfs/Datasheets/Broadcom/BCM4329.pdf
http://www.broadcom.com/products/Bluetooth/Bluetooth-RF-Silicon-and-Software-Solutions/BCM4329
I've read everything there is about this, and have yet to see anyone get it working. I don't have nearly enough experience to even take a stab at it, but I would love it.
The only phone I've seen where it was implemented was my first sprint phone: LG FUSIC, And I used it all the time.
yea im hoping some one actually tries to get it working
apple products use this same chips interesting...
http://jaxov.com/2010/04/ipad-can-play-fm-radio-broadcom-bcm4329-chip-found-by-ifixit/
i would love to see this working
I think I read about this before the EVO was released and a bunch of people got all excited but nothing ever really happened!
http://forum.xda-developers.com/showthread.php?t=693253
Not trying to rain on anyone's parade because this would be cool if it actually took off the ground BUT I doubt it will go anywhere because two reasons in my opinion!
1. Is easier to just buy a FM transmitter, some as low 35 dollars
http://www.amazon.com/Generation-Transmitter-integrated-Gomadic-TipExchange/dp/B0045DIQ9K
2. The developers on here have soooo much on their plate already. For example I think everyone would rather have Sense 3.0 up and running instead of this.........BUT like I said before, I'm not trying to rain on any parade! I for one would donate, support or whatever if we could actually get someone working on this ASAP.
That is all....LOL
I think this is just as important as HDMI and 4G.
In all honesty, I've never used HDMI or 4G.
This on the otherhand, is something I'd use everyday, as would many others.
Good luck to those who take it upon themselves to become immersed in this project.
I'd love to see this come off the ground.
~ I'm a fungi
Edit: one thing comes to mind....
What would be used as an antenna?
i think that is the biggest prob the headphones act as a headphone for the fm transmitter that would prob mean we would have to have headphones in to see any real use out of this thing
filebug said:
i think that is the biggest prob the headphones act as a headphone for the fm transmitter that would prob mean we would have to have headphones in to see any real use out of this thing
Click to expand...
Click to collapse
That, to me, seems like the smallest problem...
~ I'm a fungi
From what I've read the antenna is already built in.
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a senile fungus said:
That, to me, seems like the smallest problem...
~ I'm a fungi
Click to expand...
Click to collapse
He means the headphones act as an antenna, which defeats the purpose of the transmitter, at least for me, since the purpose of the transmitter, in my case, is to broadcast my music to my car radio.
And to the guy who said the antenna is built in, if you try to use the FM radio, it will tell you you need to plug in headphones to use as an antenna. At least, the MIUI radio did.
Yes but that is stock app. If an app is built you can over ride that request.
The reason for the headphones is obviously get better reception.
They wouldn't be needed BC the FM would only need to transmit about 5 to 10 feet.
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dtr145r said:
Yes but that is stock app. If an app is built you can over ride that request.
The reason for the headphones is obviously get better reception.
They wouldn't be needed BC the FM would only need to transmit about 5 to 10 feet.
Sent from my PC36100 using XDA Premium App
Click to expand...
Click to collapse
Actually you would need an antenna. Take a blank headphone plug and plug it into the headphone jack to enable the receiver then try to tune in a radio station. Unless you a very close to the transmitting station you are not going to hear much other than hiss. Receivers are not as picky to antenna length as transmitters are. As long as the length of wire is close to the resonant frequency in length a receiver will operate fine. With transmitters you are now pushing a current through it. If the antenna is not there, or cut close to the resonant operating frequency that RF energy will be reflected back into the transmitter causing it to heat up,and eventually fail.
In our EVO's there are several antennas inside. Mainly for connecting to cellular, 3g, 4g, BT/WiFi on the UHF bands. FM broadcast is on the lower portion of the VHF band. So the FMBC antenna (3meters) will be considerably longer than say lower CDMA antenna (42cm). The higher the frequency the shorter the wavelength (and antenna).
http://en.wikipedia.org/wiki/Cellular_frequencies#Frequency_bands_used_in_the_United_States
To fashion an antenna for this project you would need a blank headphone plug, some sort of material to fashion a dipole antenna (if you or someone you know makes plastic models the left over plastic would be perfect. Wood is not a good insulator to this project), and very thin insulated (painted) speaker wire. now for a full wave antenna you will need about 9 feet of wire (you can shorten it to 1/2, or 1/4 wave). Take the plastic rods from a model kit and fashion it into a T placing the lower part of the T into the plug then running the wires from the appropriate connections in the plug up to the top portion of the T then winding the wire out to each end. Effectively making a loaded dipole antenna.
Now I skipped alot of stuff because I don't have all the information on the chip used so I don't know if it has a tuning circuit for loading the transmitting antenna or not. You may have to add a capacitor at the top of the T between the two stubs to properly tune it. the reason I chose a dipole over a omnidirectional (whip) is because the dipole is more efficient, and easier to tune. As a matter of fact the antennas in most cellphones are now dipoles. Since most phones now have to operate hands free the omnidirectional (whip) is impractical since our hands were used as the groundplane.
Hope this helps.
Where's teamwin at .....
Igotsanevo4g said:
Where's teamwin at .....
Click to expand...
Click to collapse
now thats the comment I was anticipating.
So do all those FM transmitters we buy have 9ft of wire for the antenna?
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aimbdd said:
So do all those FM transmitters we buy have 9ft of wire for the antenna?
Sent from my PC36100 using XDA Premium App
Click to expand...
Click to collapse
More than likely no. The use loading coils, and coil-capacitor circuits. Depending on which is cheaper at the moment, and enclosure size.
For a fullwave antenna yes. Several things you can do to "shorten" it. You can coil it, you can cut it to the appropriate wavelength (1/2, 1/4, or 1/8th wave), and coil it. The drawback is once you shorten it either way you narrow the bandwidth, and the ability to properly tune it to whatever frequency you set the transmitter to.
For example using the full sized antenna you are able to use the transmitter the full broadcast band (87MHz-107.5MHz) with it not going out of tune causing power loss, and power being reflected back to the transmitter itself. Shorten the antenna to a 1/2 wave (4.5') you may be only be able to tune from say 95MHz to 102MHz, and so on. Effectively you are narrowing the amount of usable bandwidth you can use. now you can make an L-C (capacitor-coil) circuit so you can use the full spectrum but you will incur line losses so your effective radiated power will be lower (not that you had much to begin with). Depending on your receiver that you would be transmitting to the lower power may lead to more outside interference (ie noise).
ive been trying to find the pin out for the broadcom chip but i cant find it anywhere.
dtr145r said:
ive been trying to find the pin out for the broadcom chip but i cant find it anywhere.
Click to expand...
Click to collapse
I've been trying as well. Broadcom posted almost every other chip's datasheet, but not that one.. I am going to call Broadcom's tech support line on Monday and see if I can get one out of them besides that crappy incomplete block diagram in the promo handout. Know anybody that has the actual schematic for the EVO? That would even be more helpful. Then you would know what is, and what is not connected. Plus you wouldn't have to tear one down to check the connections.
any update?, this is a very good idea for everybody that don't have a bluetooth radio.
i can't wait for somebody to get this going
bump bump.
Plz do not comment on this thread.
This thread is just for posting my chapters of C programing in http://forum.xda-developers.com/showthread.php?p=32778306 this thread.
if you wanna comment or ask doubt comment here : http://forum.xda-developers.com/showthread.php?p=32756564
Chapter 1
Lets Talk about programs:
So all of us have heard about the words like programming, programs , code , decode, etc etc ..
but we don't know the meaning of it.. so here it goes..
♣What is a program and programming?
-> For computer to work , we need to give some instructions. This instruction is know as CODE. Where in Each line of code instructs the computer to do something. Set of lines of these codes is commonly known as an program. (this was in common words)
As the definition of program says:
->A computer is designed to accept input, process it and generate output. A set of instructions to perform a task is known as a program. Simmilarly, A set of programs together form an Application.
-> Coding The codes above is known as Programming.
Ohk . Cool . Now lets start learning About flowcharts
♣What is FlowChart? Why use it?
->Flow chart is a graphical representation of a program. It is useful when you are working in a team. Lets say you and me are building a project in C language n you want to show me what u are thinking about the program. you would write in C n compile the program and would show me . But i may not understand how the program worked , in other words i may not understand THE FLOW OF THE PROGRAM you made. So for that reason you make a flow chart of your program on a piece of paper, and then i would understand what you made.
AND flowchart is just like a representation of your program, it is nothing to do with programing.. you cannot put the flowchart in some file in pc n compile n run it . its not possible ..
-> Flow charts are help full in developing complex programs . You will realize it as we go further with the tutorial . I bet you will make a flow chart when you are thinking of a program but you wouldnt know how to put that into set of codes. That is when you would need flow charts.
Chapter 2
FlowCharts
Theory
As Flow Chart is a graphical representation of programs, we need symbols which will help us to graphically represent it. so here they are:
{
"lightbox_close": "Close",
"lightbox_next": "Next",
"lightbox_previous": "Previous",
"lightbox_error": "The requested content cannot be loaded. Please try again later.",
"lightbox_start_slideshow": "Start slideshow",
"lightbox_stop_slideshow": "Stop slideshow",
"lightbox_full_screen": "Full screen",
"lightbox_thumbnails": "Thumbnails",
"lightbox_download": "Download",
"lightbox_share": "Share",
"lightbox_zoom": "Zoom",
"lightbox_new_window": "New window",
"lightbox_toggle_sidebar": "Toggle sidebar"
}
Input:
The Input symbol is used when the user has to input something , in other words it denotes that user will input at this point of program.
eg: the program is about multiplying the two numbers, so the program will ask the user to input two numbers to multiply in this box, 2 and 4
Processing:
The Processing symbol is used to show that there will be some processing in the program now.
eg: after the two numbers are accepted, the process of multiplication is shown in this box. 2 * 4
Output:
The result after processing is done, ie after the two numbers are multiplied , the output is given to the user by this symbol.
eg: 2 * 4 = 8
Decision:
Some times , its essential for the program to make decisions, this can be achieved with the use of this symbol
eg: If you want the user to input two numbers two multiply, but both the numbers should be less then 5, here u can check if the user has given input as per that , if yes then the program will execute(do the work) the way u code for yes, if no then you have to code a different set of code or re run the program.
Subroutine:
This is usefull when you have a big program , you can make different flow charts and then add them together.
Flow Lines:
These are the Lines That will decide where your program will go .
Terminator::
It is like a start for each flowchart, and also the end of flowchart. Also known as Entry point of flow chart and Exit point of flochart.
On page connector:
When your program has the decision boxes, and different conditions satisfy in a different way and end up in a place is where you would use On page connector.
Off page connector:
When your program exceeds the page, and you continue it on some other page then we use Off page connector.
Annotation:
It is a type of comments, which you write for other developers if the part/logic of the part of your program is hard.
================================================== ================================================== ================================================== ==================================================
PracticalLets take an example, that a friend of your asks u to make a program on how to make a tea.
n u say ya ok bro, i will make a flow chart n will send it to you.
so here is the flow chart that you would make
So heres the first flow chart .
lets discuss it in detail (remember the red numbers are just so that you know what i am talking about, u need not write it while drawing flowcharts).
1. It is the terminator. It denotes that your program has started
2. It is the annotation, it is just for the reference of the reader. it is as good as an comment.
3. It is an input box, asks the user to input water, sugar , tea leaves and milk
4. It is an processing box, in this box processes takes place, in this case it is boiling the milk.
5. It is an output box, it tells that the tea is prepared.
6. It is an terminator. It denotes that your program has ended.
================================================== ==================================================*
Lets Take another example:
Suppose i ask you to make a flow chart of how do users register them self at Xda-developers.com.
How would u make it?
Something like this:
So , as you can see,
The terminal is starting the program, then the user inputs his details that are neccesary for signing up(in input box). then those details are stored in the xda developers database(in processing box) , and then the output box shows that you are registered sucessfully..
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So after seeing two flowcharts i guess you got a better understanding of what flowchart is all about..
So the flowcharts start with a start terminal. and ends with stop terminal. And then there are input boxes for taking inputs and processing boxes for processing the input and there is an output box for output.
So far we learned how to use:
1) Terminator
2) Input Box
3) Processing Box
4) Output Box..
Lets Give you guys an Exercise... At the end of this Post i will put it up.
Now before we move on to use the Decision Box i would like to Show you one more simple flow chart (and if you dont understand it , then i guess i am going too fast in my teaching.. lemme know if you dont get it , pm me or mail me )[/I]
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Decision Box
So while in a program sometimes you have to make decisions.
Decisions like if the user input is right or wrong, username is less than 16 character, password is atleast 6 character etc etc.
This is when you use Decision Box in flow chart.
It is used as follows
When the user is signing up in xda-forum . this is the decision box used after the password is accepted.
It checks , "Is the password greater than 6 characters?, if yes then run so and so codes, if no then run so and so codes" The flow line of Yes have different set of codes. The flow line of No have different set of codes.
For eg:
as you can see , in the decision box, if the Username is greater than 16 characters it shows an error and then runs the program again from where the flow line indicates. If the user name is not greadter than 16 characters then it runs the program normally
Exercise::
Draw FlowCharts For the following programs:
1) To Add two numbers.
2) To multiply the numbers
3) Add two numbers which are single digit only and show appropriate error if user inputs a two digit number
(Hint: Use the decision box to check "is number1 < 10" as if the number will be less than 10 then it will be a single digit number , (we exclude the posibility of negative numbers for sake of simplicity , though will teach you to tackle it in the next chapter))4) Add the two numbers and subtract the addition with their product (eg if the user inputs 2 and 3 , then in processing box write (2*3)-(2+3) )
This Fourth one is important , plz do not skip it as we will discuss on it in next chapter.
Do it on a paper or in book.
mail me at [email protected] your scaned copy or a photo of your flowchart if you want to .. i will see each of them
Or Check From The answers Below.
Answers:
1) Answer
2) Answer
3) Answer
4) Answer
Chapter 3
FlowCharts(...Continued)I hope you have done the exercises and have checked the answers and rectified yourself if you were wrong.
Still i would like to discuss the 4th Problem of the Exercise as i Had some purpose for giving that sum.
So when you were doing the flow chart , you would have encountered a problem.
Lets not go to flow chart directly, lets talk on it as if it were a math problem .
Add the two numbers and subtract the addition with their product: (considering the two numbers are 2 and 3)
Code:
Let the two numbers be a and b.
a=2
b=3
a + b = 5
a x b = 6
(a x b) - (a + b) = 1
NOTE:
You know there are variables in maths?? like x = 2 or x= 7 or y = 10 etc etc..
Ever thought why they are called variables??
It is because their values keep on changing in other words "The value of x VARIATE"
Just Keep it in mind, i would ask you to recollect it after done with this 4th Flowchart Problem
Doesnt it seem too long and boring to write(m talking about (a x b) - (a + b) )?
That's where the flowcharts and all the computer programming languages have a plus point . You will realize it in a minute..
See the flow chart:
See the names underlined with red ink. Sum , Product and Answer.
(referring the flowchart with the above mathematical representation)
Here, when a+b is calculated , the answer is stored in "Sum"
ie:
Code:
Sum= a + b
Similarly, when a x b is calculated , the answer is stored in "Product"
ie:
Code:
Product = a x b
When Product(ie a x b) is subtracted to Sum(ie a+b) it is stored in "Answer"
ie:
Code:
Answer = Product - Sum
Recollect the note above, about the variables and read bellow.
What is a Variable?
-> Variable is a vessel that holds a Value . Where as this value is known as constant.
Eg: x , y , z , a , b , c etc etc
What is Constant?
-> Constant is that value that is stored in a Variable.
Eg, 1 , 2 , 3 , 4 , 5 , 6 etc etc
In all the flow chart above,
These were the variables you used:
Number 1
Number 2
Sum
Product
Answer
You can use the Variable Number 1 again and the value of Number 1 in a different flow chart would be different . Hence it is a variable.
But in any flow chart the value of "1" will remain "1" only.. it wont ever be like 1 = 2.
Hope you are getting my point.
This variable is not just for Flow Chart. Learn Any programing , the knowledge of what is variable and constants is necessary , its like the most basic thing .
So to Sum up and give a summary of variables and constants,
A variable is something like a vessel , a vessel that holds the constants. Constants are the values that are stored in vessel which is nothing but a Variable.
We will talk on this later again when we start the c programming.
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As in maths , Constants are limited to numbers. For eg , X = 10 , Y = 15 etc etc
But this is not the case with flowchart , In flowchart you can even write a word or a sentence in a variable.
Eg,
Day = " Wednesday"
Month = " October"
Name = " Mihir"
Birthdate = "1st January 0000"
Mobile no = " 123456789"
Pi = "3.148"
Etc etc...
So as you can widely distinguish , variables in FlowCharts are of 2 Types,
1) Character Variable, Eg, Name = "XDA"
2) Numeric Variable(also known as Integer variables , as Integer contains all the numbers ) , Eg, Num = " 12345"
So when you make flow chart you have to Define all the variables you use if they are number? or they are Character?
See the flow chart below to understand how.
As you can see everything is new in this flowchart.
This is the way we represent a program in a better way in flowchart.
Let me explain to you all of its components.
All of which is written in green above, is like a system command sort of a thing.
And all the red color text are variables.
And all of the blue color things are Operators ( mean + , - , x , = etc, we will talk all about operators in next chapter)
System:
START starts the program
NUMERIC defines that the following variables are Integers/numbers and is written always in processing box. (this process is called DECLARATION we will talk about it in a while).
ACCEPT Accepts constants from the user and stores it in the Variable, always written in input box.
DISPLAY Displays the constants stored in the variable.
STOP Stop/terminates the flowchart/program
Meaning of Declaration!
=> When you want to use a variable, lets suppose u want a variable Num1 , Then you first have to tell the computer that:
"Hey bro, i am using a variable named Num1 in my program which is a numeric variable"
which in flowchart is written as :
Code:
[COLOR="SeaGreen"][B]NUMERIC[/B][/COLOR] [B][COLOR="Red"]nNum1[/COLOR][/B]
As you can see that we are talking to the computer and telling that we are using the variable of this name , it is AS good AS a process?
Hence, it is written in a Processing Box.
As you can see i am prefixing all the numeric variables with n , and you might be wondering , what is this crazy guy talking ?
Basically,
All the variables are prefixed to show what type of variable it is when we use them .
meaning, when we use a numeric variable , we prefix it with n, when we use a character variable we prefix it with c
You can name the variable what ever you like , a, b ,c sum , interest , principle,Name, blah blah etc etc.. anything you like cuz when you will write it in flow chart it will be like nSum, nInterest, nPrinciple , cName. So u will know that Sum ,interest & Principle are numeric variables and Name is a Character variable. Hope now you understand whats the use of prefixing n and c in variable name.
Lets talk about the above flow chart step wise now(referring the numbers in the image above):
After the program starts,
1. There is a Process box. As you know it declares (recollect, declaration means to tell computer that you are using this variable) the variable, hence it is in the process box. In this box the Variables are declared as Numeric and hence are prefixed with n .
2. There is a Input box. What do we do in input box? we take input , and hence there is a proper word defined for it . Accept , and we then write all the variables that we want the values of , from the user.
3. There is a processing box, It adds the two numbers and then stores the value in the Variable Sum which is numeric ( nSum) (it will be clear when i teach you operators in next chapter)
4. There is a Output box, its purpose is to DISPLAY , hence we write Display and then we write all the variables in the Output box that we want to display.
and the program terminates..
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Dont give up, let the things sink in. It will take time , you will learn! Trust your self
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I would like to advice you to read this again. As you will get a better understanding of it now. And i have added some things in it so dont skip it.
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Input:
The Input symbol is used when the user has to input something , in other words it denotes that user will input at this point of program.
eg: the program is about multiplying the two numbers, so the program will ask the user to input two numbers to multiply in this box, 2 and 4
When you want to accept the values from user , you write it in an Input Box. lets suppose you want to Add two numbers , for that you need Three Variables, One variable for storing The first number, second variable for storing the second number , third variable for storing the value of the addition of two variables. And lets name these variables now, nNum1,nNum2 and nSum. So how will you write it in input box?
This way
"Accept nNum1 and nNum2"
Processing:
The Processing symbol is used to show that there will be some processing in the program now.
eg: after the two numbers are accepted, the process of multiplication is shown in this box. 2 * 4
Two things that can be in processes :
The first process box is above, it is used to declare variable with its type,
lets consider the same above example , then u wud write it
"Numeric nNum1, nNum2 and nNum3"
And then you need to add those numbers? correct so you would add it in another processing box like this:
"nSum = nNum1 + nNum2 "
Output:
The result after processing is done, ie after the two numbers are multiplied , the output is given to the user by this symbol.
eg: 2 * 4 = 8
The main purpose of Output box is to show the output.
See the pic below
As we want to display , so we write "Display" in this box. Suppose you want to display Sum calculated above, you would do it this way:
"Display nSum".
We can also write what ever we want in double inverted comas.
Eg
Code:
Display "Hie this is Mihir"
You can even append a variable after it, the constant stored in that variable will be displayed,
Lets suppose there is a variable nNum , in which the Mobile number of a user is saved and the number is 123456789, then you can display it this way:
Code:
Display "Your Mobile number is" nNum
This will display , Your Mobile number is 123456789
Decision:
Some times , its essential for the program to make decisions, this can be achieved with the use of this symbol
eg: If you want the user to input two numbers two multiply, but both the numbers should be less then 5, here u can check if the user has given input as per that , if yes then the program will execute(do the work) the way u code for yes, if no then you have to code a different set of code or re run the program.
Here checking statement means to check something. Eg nSum < 10 or nSum > 10 , nNum <100 etc etc (as of now it consists only of Single Check statement , like you can just see if its a variable is less that 100 and similar things . You cant compare it with two things like a variable is greater than 50 but is less than 100. As of now i cant. We first have to understand operators, after done with operators , we will come back here and talk about it.)
If you were to check if the nSum is less than 100 you would write:
"Is nSum<100 ?"
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Plz read the output box again i have added something. This is for the users who have read the post yest. And i have edited it just now.
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A flow chart for registration.
i guess you can now understand this flowchart above , and i need not explain it to you.
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Chapter 4
Operators
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Hope the above image , clears your mind about what is variable and constants.. If you still have any confusion about variables and constants then mail me at helpline mail : [email protected] or PM me..
I devote this chapter to Operators..
Operators: The symbols used to make the computer do an operation is know as an operator .
There are various various types of operators:
1)Arithmetical Operators
2)Conditional Operators
3)Relational Operators
1)Arithmetical Operators :
-> Operators used for doing mathematical operations is know as arithmetical operators. This includes the following :
=
+
-
*
/
%
you may be familiar with all the mathematical expressions above, rather than this, one %.
This is not a percentage , its a modulor division operator. Its name is Modulus.
The division operator yields the Quotient as an answer, where as Modulus yields the Remainder as an Answer.
as you can see above,
when you write an expression as 13/2 it will yield an ans 6 . Therefore, 13/2 is 6 or may be 6.5 (calculation in flowchart is not so precise as it is just to understand the flow of the program and not for calculations)
when you write an expression as 13%2 it will yield an ans 1. Therefore, 13%2 is 1.
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2)Conditional Operators
Operators that define conditions are known as conditional operators.
They include these
|
&
This | is "OR" operator. It is used when you want to define any conditions like : a<10|a>15. This means either a is less than 10 OR it is greater than 15 , then its yes . (refering to the decision box, cuz thats the only place where you want to put up conditions right?) Only one of the two conditions must be satisfied , in order to make it a YES
If not even one condition is satisfied then it is a NO , n it will run different set of codes .
Image below will help you understand it.
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The second operator is & "AND" operator. This is used when you want conditions like : a>100&a<200. in this , a should be greater than 100 AND a should also be less than 200 , if both the conditions satisfy then only it is a yes, if either of the condition is not satisfied, then its a no.
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3)Relational operators:
->Operators used for relating two variables are known as Relational Operators
They are as follows:
==
<
>
<=
>=
!=
Note: '=' is used to assign the value, eg , a=4, this means a is equal to 4, where as , a==4 , is a relational operator, it checks , IS a is equal to 4?
The two operators == and != are new to you, i explained the first one above,
the second one != is "not equal to", it is used to check , eg , Is a!=4?,if a is not equal to 4 thn its a yes, if a is equal to 4 then its a no.
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A flow chart to check whether the number input by the user is positive or negative?
Try this on your own , n then see the answer below,
You would notice , there is a circle after the processing box..
It is an on page conector. When more than one flow lines are conected to something , then this is used, (i havent used it in any of the above eg of flowcharts, just to teach you bit by bit.)
This is what i used before:
this is what is to be used :
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This was it Small Chapter 4. On operators..
If you have done this much ,then be proud of your self, cuz u have learned half of the basics of C programming
Next chapter it about Subroutine and off page conector. And then we will commence out voyage in C programming
Chapter 5
Subroutines And Off-Page-Connector
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So as you have seen many flow charts above, u have came to an end of learning the flow chart, are are soon going to learn about C programming.
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So lets talk about Subroutine:
What is Subroutine?
-> It is a symbol used in Flow charts to represent the programs clearly.
You will understand it after you see the flow chart bellow.
Lets suppose you were to make a program to add the numbers (we did it before in Chapter 3) , but using subroutine makes it tidy graphical Representation , and also it is easy to understand while reading it. :
As you can see above , the function of adding the two numbers is separated from the flowchart for better representation , this is known as an Modular Approach of Programming.
(not talking just about FlowCharts , i Am talking of C programming language .)
Modular Approach of programming is , to keep the main code in a file , and then the operating codes in a separate file , as you can see above, the main code is separated from the code that adds the numbers.
It is not of a great help when such a small flowchart, but when u have a full calculator in which you would add , subtract , multiply , divide etc etc , this approach would be the best . :good:
NOTE:at the end of the subroutine , we use a terminator with "RETURN" , and not "STOP"
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Lets take another Example.:
You wanted to make a flowchart of a program , a program that adds and subtracts both .
Then it would be represented this way :
(all the three images is one FlowChart Only)
Each image above is like a different page in a book.
So if your flow chart ever exceeds the page in a book or page in any document, then you use the off page Connector.
Lets first talk about subroutine.
As u can see above, the Subroutines add and subtract are separated from the flowchart , you can write it on any page as long as those pages are kept together .
When the page comes to an end, we use a Off-Page-Connector, and then name it what ever we like, and in a new page we make a new Off-Page-Connector with the same name, as you can see a connector with name "A" is on the both page, so the connector "A" on the first page , conects with the conector "A" on the second page , Same way with the connectors named "B"
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One more eg and we are done With Flowcharts
A flowchart , to show a program .
The program takes the marks of the students who gave an entrance exam for College, Subjects are Math,English and French. If in each subject a student scores atleast 35 marks and the average of the 3 subject is atleast 50 marks , Then a selection letter from the college is sent , if not , then a rejection letter is sent. Also count the number of selection letters and rejection letters sent.
Note:I wont explain this flow chart. If you can understand it on your own then you are good to go further with C programming , if you cant then please read the chapters again and try understanding it again and then proceed with programming.
The only new thing in this is :
nSelect = nSelect + 1
Lets suppose nSelect is a variable with a value 0 in it , then you can say
nSelect = nSelect + 1 which means , nSelect = 0 + 1
And then suppose nSelect is 1 then
nSelect = nSelect + 1 means nSelect = 1+1 which comes to two.
You can use such type of statements in programing .
Remember ,
The Right Hand Side of an equation is calculated and then stored in the variable Left Hand Side,
NSelect + 1 is calculated and the ans is stored in nSelect on the Left Hand Side. It works as an counter.
And yeah!! you are done with flowcharts.. We will start with Programming ASAP ..
C Programming Begins!!!
So today we would have started with C programming ,but according to me and my fellow developer friend with whom i discussed of how to teach it to you and decided that we will teach you some extra things. As we are secondarily studying this for learning Android stuff though not only for android , we will try to teach everything about C but we will also try to teach you some extra things that will be helpful while you start with your android development .
So the main things are :
What is Computer?
What is an Operating System?
Where is C usefull in all this?
What is android?
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What is computer?
-> The definition of computer have changed as it has got many changes in it. Years before when computer wasnt invented , the person who used to do calculations was referred as a Computer as he used compute the Mathematical problems. But as the machine was invented to do the calculation , The machine was then named as "Computer".
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What is a Operating System?
=> Years Ago when computer was first invented,
it had a monitor of small size, one full room of chips and stuff (today it fits into a small box and we call it CPU) the name of the room was Central Processing Unit , (the room was the core of the computer , and as you know a room is also called as a Unit) . That room used to get commands from other room where the input from user was taken , and then processed and sent back to the same room for displaying it on Monitor. Hence it was a processing room too. So the room with chips used to Process things , it was the Core thing and hence it is named as Central Processing Unit(CPU).
(If you are interested in all the things I said above, then you must study Computer Architecture , as study of all these stuff is known as Computer Architecture .)
When this Computer was invented , it was just for the sake of calculation , you can say it was a 2 room huge calculator. And when you start the computer , You just see a black screen , and then you had to write the whole calculator program in a programming language you like (idk what language was used at that time ) and then do the work. The calculator program was very huge and it was very tiring job of writing it everytime you turn on the computer. So then someone invented "something" that stored the things in it. This "something" was named as Memory. As it stored the calculator program, it was kind of a Memory for the Brain(CPU) of the computer, Hence named as Memory. (This memory was very small it wasnt even 1kb ) And then the Calculator Program was written again and then stored to the memory . So everytime you turn on the Computer you dont have to Write the whole calculator program you just have to write some set of codes to go to memory and run that calculator program. Eventually when the need of computers increased from just calculation to many other Office work , like Storing the customer information, making the list of expenses and profits of an company many such applications were made . But still to run any of these application , some set of codes were neccesary and hence it was useless till some extent for normal people. So a new era was started, The era of operating systems. It was like you will have applications for using APPLICATIONS, eg if you want to use calculator in windows operating system, you will go to Start menu and then accesories and then select calculator. This is called GUI, meaning Graphical User Interface. Today we can make a folder by right clicking and selecting "New Folder" this wasnt the scenerio at that point of time , they had some set of commands to create a folder.(even today you can make a folder with this command in Command Prompt "mkdir NewFolder" mkdir meaning make directory , and then "NewFolder" is the name of the folder. If we want to see what folders we have in c drive, we just go to MyComputer and then go to c drive, this wasnt the case at that time, they had to write set of commands to navigate till that directory , and then had another command to List all the files and folders in that place. So everything was based on Commands Given by the User. So an need of Operating System was essential , where in commands were given by user interface(eg right clicking and making a folder is as good as opening command prompt, navigating to the location and then giving commands to make a new folder .) So when all these things are put together and then the need of Commands is decrease for day to day work , this package of software is known as Operating System.
There are different companies making Operating Systems depending upon the hardware capabilities of a Computer. eg, Windows, Linux and Mac(apple).
Note: The Definition of an Operating System is way too big than i explained above, but this is what you should know as of now.
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Where is C usefull in all this?
=> The whole operating System is made in C language. It is a fact that, Windows consists of 13,000 lines of codes where in only 800 lines are not writen in C launguage . Now you can see what is the value of C . (will be writing C rather than C language ) C is widely used in making Operating Systems , Games and Kernels in other electronic Devices.
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What is kernel?
=> A set of codes writen in C language that lets the Software and the Hardware communicate is known as kernel. For eg , if you press the volume Down button (hardware) how does android phone knows that the volume down button was pressed and the he has to lower the volume by a level in the phone?
See the image below:
The Hardware says the kernel that the user wants to lower the volume , the kernel comunicates with Operating System(OS) and tells to lower the volume by one level , and then it displays that the volume is decreased .
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Why C in everything?
=> C is widely used in everything because it is very fast as it is in direct contact with Hardware via kernels. So it is faster than any other programming language. It is not only used in computers. The Food Processor with Timing, the Tv Remote etc everything has C in it.
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What is Android?
=> Android can be simpt explained by saying "The mobile version of Linux is known as Android"
This was just a chapter for some extra information that would be usefull in your future when you will start doing some work in android or windows, or even when you will try to make some programs in C while you are learning from this tutorial.
Chapter 1 Theory On C prgramming
So basically What is C?
=> C is a programming language developed at AT & T's Bell Laboratories of USA in 1972. It was designed and written by only one person "Dennis Ritchie". In the late seventies C began to replace the other programming languages like PL/I,ALGOL,etc. No one pushed C neither was it 'official' Bell Labs language nor was it advertised by any means. Still C's reputation spread and its pool of users grew. Ritchie seems to have been rather surprised that so many programmers preferred C over the older languages, including FORTRAN. Still it is choosen over the newer languages like PASCAL and APL.
Probbaly , why C seems so popular is because it is reliable, simple and easy to use. Moreover, In an industry where newer languages, tools and technologies emerge and vanish day in and day out, a language that has survived for more than three decades has to be really good.
An opinion that is often heard today is -
"C has already superceded by languages like C++, C# and Java, so why bother to learn C today!!". I seriously beg to differ with this opinion. There are several reasons for this(according to the aurthor of the book "Let Us C"-Yashwant Kanetkar, and i agree with him):
I believer that nobody can learn C++ or Java directly. This is because while learning these languages you have things like Classes , Objects, Inheritance , polymorphism , Templates , etc. and also the elements like loop , if-else, nested if-else, switch,etc. These elements like loop etc should be learned in C , then about objects in C++ and then Exception handling in Java , so it is like a proper flow in the boat of Knowledge. Though this Three-Step learning process may take more time, but at the end of it you will definitely find it worth the trouble.
C++,C# or Java make use of principle called Object Oriented Programming(OOP) to organize the program. This organizing principle has lots of advantages to offer . But eve while using this organizing principle you would still need a good hold over the language elements of C and the basic programming Skill
Though many C++ and Java based tools and frameworks have evoleved over the years the importance of C is still unchanged because knowingly or unknowingly while using these frameworks and tools you would be still required to use the core C language elements -another good reason whu one should learn C before C++ , C# or Java.
Major parts of popular operating system like Windows, UNIX, Linux are still written in C (As we talked on it earlier) This is because even today when it comes to performance (speed of execution Nothing beats c) Moreover, if one is to extend the operating system to work with new devices one needs to write device driver programs. This programs are exclusively written in C (this is what you will do when you will build android kernels after learning C)
Mobile devices like Cellular phones and palmtops have become rage of today. Also, common consumer devices like mirowaveovens , washing machines and digital cameras are getting smarter by the day. This smartness comes from a microprocessor, an operating system and program embedded in this devices. These programs not only have to run fast but also have to work in limited amount of memory. No wonder that such programs are written in C. With these costraints on time and space, C is the language of choice while building such operating system and programs.
You must have seen several professional 3F computer games where the user navigates some object, like say a spaceship and fires bullets at the invaders. The essence of all such games is speed. Needless to say, such games wont become popular if they take a long time to move the spaceship or to fire a bullet . To match the expectations of the player the game has to react fast to the user inputs. This is where C language scores over the other languages. Many popular gaming frameworks have been built using C language
At times one is required to very closely interact with the hardware devices. Since C provides several languages elements that make this interaction feasible without compromising the performance, it is the preferred choice of the programmer.
I hope that these are very convincing reasons why you should adopt C as the first and the very important step in your quest for learning programming languages.
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Getting Started with CCommunicating with a computer involces speaking the language the computer understands , which immediately rules out English as the language of communication with computer. However, there is a close analogy between learning English language and learning C language. The best method to learn English is to first learn the alphabets used in the language , then learn to combine these alphabets to form words, which , in turn, are combined to form sentences and sentences are combined to form paragraphs. Learning C is similar and easier . Instead of straight-away learning how to write programs , we must first know what alphabets, number and special symbols are used in C , then how using them,constants, variables and keywords are constructed and finally, how are these combined to form an instruction. It is illustrated below:
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C Character SetA character denotes any alphabet, digit or special symbol used to represent information. The Valid aplphabets, numbers and special symbols allowed in C are :
We would talk about what are variables,constants and keywords and set up the programming environment and also make our first prorgram with its flowchart
CHAPTER 2
I can bet you will relate most of the things with C programming , from flowcharts.
When you run an application , it first reserves the memory required for it to run . Lets suppose you are playing a game on computer, "pinball", this game will first reserve the memory locations in the RAM or storage. And then only THE PINBALL game can access those memory locations. The image below depicts is properly.
as you can see above , memory is made up of cells, each cell has its address (0x111 to 0x142 are the adresses, dont worry about the numbers like 0x111 n stuff i just wrote it to show you , the real memory locations are like 2031576,2031577,2031578,2031579 and so on. We will see it in real when we go further down with the chapters )
Lets say your computer has a memory from 0x000 to 0x999, and then you open the pinball game , the pinball game needs 32memory cells, and it started getting cells from 0x111 and then reserved till 0x142 so that it can run smoothly , and lets suppose you open another app in backgroud , lets say you opened Calculator, and also suppose Calculator needs 50 cells of memory , then it willl start from 0x143 to 0x193.
These cells are nothing but Bytes.
1Gigabyte = 1000Mega Byte
1MegaByte= 1000 Killobyte
1Kilobyte = 1000 byte
This is what we know right? its wrong
1Gigabyte = 1024 Mega Byte
1MegaByte= 1024 Killobyte
1Kilobyte = 1024 byte
What is 1 byte equal to??
1byte = 8bits
NOTE: Google this "1 byte = how many bits"
You will see this at the start , as you can see it works like a converter, just goof around with it have a lil fun n learn mean while.
This was just off topic things, but keep these things in mind while learning C , this is like the general knowledge required for learning C , so now we are starting with Real C programming.
===================================================================================
So now what is variables?
Various Definitions:
Code:
"A variable is the name for a place in the computer's memory where you store some data."
"A variable is a way of referring to a memory location used in a computer program. "
Lets not go into theory again , lets talk about a program in which you want to add two numbers.
First of all you want to accept 2 numbers from users , add them and then store it to another variable?
Lets say you accept two numbers 'x' and 'y' from the user , you cant just write x + y, right? cuz x + y what? you will have to use one more variable 'z' and then store the value sum of 'x' and 'y' in it. ie z=x+y
so now here the three variable 'x' , 'y' and 'z' are variables, agreed?
so these variables WILL be stored in memory?
Each of them will use their own memory cells? or to be precise each one of the variable will use a BYTE from memory?
lets say the three memory locations used are 0x200,0x201,0x202
So you can conclude that the NICKNAMES of the memory location 0x200,0x201,0x202 , are 'x' , 'y' and 'z' respectively.
which in other words means the variable 'x' is reffering to 0x200 , so what ever you store in variable x is gonna be stored in the memory cell with address 0x200 and the same with 'y' and 'z' . so the above definitions are true, If you may read it again , you will understand better . Still you dont know what is DATA in this right? we will talk about it in a while.
What are constants?
The value of a variable is constant.
lets talk about the above program again , the variable x, y and z.
The user inputs the number 2 and 4,
so x = 2 , y = 4 and as these numbers are supposed to add and the answer is stored in z , so z=6.
now the value of x will change from program to program , if i make another program , i can use variable x and it may have a different value.
But the VALUE of value of variable , (2, is the value of x) this will never change, 2 will remain 2 , it wont ever mean 3, like 2=3 or something.
Hence it is a constant. This constant is stored in memory. The image below depicts is clearly.
============================================================================
Lets get in actoin?
So lets download the compiler now.
So the compiler we gonna use is DJGPP, it it like command line GCC (GNU C Compiler) , we will write program in notepad++, and then save it and then open up command prompt and then compile it from there and then we will get an .exe file .(dont worry if you arent getting it, everything will be taught )
Links:
DJGPP
Notepad++
How to download things?
For DJGPP:
select these fields:
The selection of Operating system may change according to your OS. If on Windows 7/vista select windows XP in that os section.
then click on tell me which files to download .
then download each of the zip file .
NOTE : If you are on linux then you have gcc compilers already, google it how to use it.
For notepad++:
go to the link above , then click on download button on left botom panel:
then:
.
===========================================================
Put the downloaded files from DJGPP in a folder named DJGPP.
now open the note pad plus plus exe and install it ..
then copy the DJGPP folder to C drive:
now open notepad++
and then write the name of the files in that DJGPP folder in the notepad++ (write unzip32 and then the file name):
and then save it as DJGPP.bat (dont forget to write .bat in that DJGPP folder..
if you have done the downlaod the way i have said and you have 8 files in the folder then copy this and paste in notepad :
Code:
unzip32 bnu2211b
unzip32 djdev203
unzip32 faq230b
unzip32 gcc472b
unzip32 mak3791b
unzip32 pakk023b
unzip32 rhid15ab
unzip32 txi412b
now go to DJGPP folder and open this DJGPP.bat file.. it will extract things for you..
now go to start menu , right click on my computer then click on properties:
now follow the instructions in the screen shots below(in some screen shots i have show the PATH in note pad, its jst to show you the path in bigger font. you need not write it on notepad):
click on advanced system properties, for windows xp users, you will have a box opened like the image below , click on advanced tab , for vista users IDK i never used Windows vista goof arround with it you will find what to do..
click on environment variables
click on path and then click on EDIT .
Note that in the path , there should be a ':' semicolon , then write c:/djgpp/bin;%PATH% , then click on ok.
now click on new
write these things in the Variable name and variable value , click on ok , then again ok then again ok. and you will be done..
now we have set up our Compiler .
Now lets write our first C program, just to check whether the compiler is running or not.
copy this and paste it in notepad++ ,
Code:
#include<stdio.h>
void main()
{
printf("Hello XDA!!!");
}
now save it with the name hello.c , dont forget to write ".c" at the end.
now open command prompt ,
write
Code:
cd desktop
then write
Code:
gcc hello.c
then write
Code:
a
if you got something like this then you are done.. if you got a error like Gcc is not an internal comand or something.. you messed it up , try the steps above from setting the environment variables.. and still you fail then you mail me at [email protected]
NOTE: Dont worry , we were just checking if its working or no , m gona teach you to use command prompt soon trust me , the boring part is over now. Its all the fun now :good:
Chapter 5 - Part II
Integer and float conversions
In last tutorial you learnt about the operators used in C programming. Now we will see about how to use them effectively, i am making this tutorial by writing it because it has some tables which will take time for you to understand, and for that its better to write it than to show it in video.
So in order to effectively develop C programs, it will be necessary to understand the rules that are used for the implicit conversion of floating point(means a float variable) and integer values in C. These are mentioned below : (read them carefully , remember float variable, floating point and real variable , all mean one and the same thing)
An arithmetic operation between an integer and integer will always yield an integer result.
Eg. 2*2=4
An operation between real and real will always yield a real result.
Eg, 2.000000 * 2.000000 = 4.000000
Point to remember: : Float variable has 6 digits after the decimal , so if you write ,
Code:
#include<stdio.h>
main()
{
float a;
a=10;
print("%f",a);
}
then it will print 10.000000 as float value has 6 digits of precision..
An operation between an integer and real will always yield a real result.
eg, 6/2.0 = 3.000000 , you see that 6 is integer , 2.0 is real and they are divided, the 6 gets promoted to real value (6.000000) and then 6.000000 is divided with 2.000000 and the answer is 3.000000
Lets list all the operators we know so far:
+ (Addition operator)
- (Subtracting operator)
* (Multiplying operator)
/ (Dividing operator)
% (Modulus)
= (Assignment operator)
== (Equality operator)
Lets suppose you were to write a expresion like this:
Code:
x=2*3+4;
Now there are two possibilities in this ,
The compiler can first multiply:
Code:
2*3
and then add 4 to it.
OR
The compiler can first add:
Code:
3+4
and then multiply it by 2.
These two possibilities can create confusions while making programs, hence to solve these, C has something known as "Operators Precedence".
See the Image Below :
As you can see, that the */% have more precedence then the + -, hence , When there is a expression like:
Code:
x=2*3+4;
First multiplication is carried out , and then it is added. and then it is assigned(the assignment operator has last precedence) to the variable in left.
NOTE: The =! is NOT EQUAL to operator and is used when you compare it. will be explained in following chapters with examples.
===========================================================================================================
In addition to these operators, there are more operators, which we will see as we need them further, and will be explained as we encounter them.,
Chapter 6 (DECISION!! DECISION!! DECISION!!)
Chapter 6
If you have a calculator which will just ADD the two numbers, then calculator will be pretty useless , wont it?
Hence,There is something in the calculator that decides whether to add or subtract or multiply the two or more numbers provided by the users. This is when we need decision control.
The C language too must be able to perform different sets of actions depending on the circumstances. Actually, this is what makes C popular and very widely usable.
C has three decision making instruction(Reminder:a line of code is instruction)
If Statement
If-Else Statement
Switch
The if StatementLike most languages, C uses the keyword(if you forgot what is keywords check out the FAQ) if to implement the decision control instruction. The syntax(look FAQ) of if statement looks like this:
Code:
if(condition)
{
[B][I]code[/I][/B];
}
where the CODE is the instructions that you want to run.
And if the CONDITION is true then the CODE is executed.
The keyword if tells the compiler that what follows the keyword if in the ( ) "parenthesis" is the condition. If this condition is true then the CODE in the pair of { } "braces" is executed. if the condition is not true then the statement is not executed, in fact the program skips it.
How to evaluate if the condition is true or false?
With the help of relational operators.(will be taught in the second part of chapter 5, when it will be updated for now just remember that the operators used for relating is known as relational operators Eg. == , !=, < , > , <= , >=.
== is to compare the right hand side with the left hand side and != means not equal and others are simple. Will be taught in detail in Chapter 5 part 2 i will link you as soon as that chapter is done by my friend.)
Lets try a program now:
Code:
//This is a coment
//A program for demonstration of [B][I]if[/I][/B]
#include<stdio.h>
main()
{
int number;
printf("Please enter a number with less than 100\n");
scanf("%d",&number);
if(number<100)
{
printf("What a good student you are!!");
}
}
NOTE:
Never put semi colon after if statement Like this
Code:
if(a<10);
printf("A is less than 10!");
As the program will think that you terminated the if statement after checking the condition , it will think of it this way
Code:
if(a<10)
{
}
printf("A is less than 10!!");
So no matter what the value of a is , it will always print A is less than 10.
A flowchart for the above program to make things clear:
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Another Eg:
If your bill is above 10$ in McDonald's then you get 5% discount, if not then no discount.
(try making a flowchart your self , and then see the C program below)
Code:
#include<stdio.h>
main()
{
float billamount;
[COLOR="Green"]/*float data type because bill can be in decimal. eg 10.40$*/[/COLOR]
int discount;
[COLOR="Green"]/*discount will remain 10% only*/[/COLOR]
float totalamount;
[COLOR="Green"]/*the amount after deducting the discount from the bill we will store the value in the "totalamount" variable*/[/COLOR]
printf("Enter your bill amount in Dollars\n");
scanf("%f",&billamount);
if(billamount>=10)
{
discount=5; //If billamount will be more than or equal to 10$ then we will give discount of 5%
}
totalamount=[COLOR="RoyalBlue"]billamount[/COLOR]-[COLOR="Red"]billamount*discount/100[/COLOR];
[COLOR="Green"]/*here [COLOR="red"]billamount*discount/100[/COLOR] is to calculate the percentage and then subtract it with the real [COLOR="RoyalBlue"]billamount[/COLOR]*/[/COLOR]
printf("The total amount is : %f",totalamount);
}
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The If Else Statement
----------------------------------------------------------------------------------------------------------------------------------------------------------------------
The if -Else statement is the real thing, the if statement was derived from it. Will explain you how and why at the end of the If-Else discussion .
The Syntax(syntax means general form )of the IF-ELSE statement is.
Code:
if(CONDITION)
{
CODE If true;
}
else
{
CODE if the CONDITION is false;
}
Lets go through it Step by step:
The CONDITION is evaluated
The CODE IF TRUE will run if the CONDITION is TRUE
if the condition is false then the CODE IF THE CONDITION IS FALSE will run.
Lets see a example
Code:
/*A program to add or subtract the numbers*/
#include<stdio.h>
main()
{
int a,b,c; /*a and b for accepting number for user and c for storing the addition or subtraction*/
char op;
printf("Hello, Please enter your operation (Addition or Subtraction only)?\n");
scanf("%d%c%d",&a,&op,&b);
if(op=='+')
{
c=a+b;
}
else
{
c=a-b;
}
printf("The answer is : %d",c);
}
Some examples tested in the program.
Found it complicated? The lets simplify:
scanf("%d%c%d",&a,&op,&b);
The %d will accept the first integer and save it in a
The %c will accept the Operator(+ or - ) and save it in op
The %d will accept the second integer and save it in b
Then the If will check if the op=='+', if it is + then it will add and store the answer in the variable c. It will skip the ELSE .
If op is not + then it will skip the if and the codes in the Else will run, meaning it will skip the codes in the if and then subtract the two integers and then store the value in variable c.
After this the printf functions prints the variable c, which is the answer.
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Revising Stuffs
---------------------------------------------------------------------------------------------------------------------------------------------------------
Let me brush up your basics again:
%d is for integers
%c is for characters
%f is for floats
Defining: To tell the computer you want a variable of int/float/char type is called as defining a variable.
Eg.
char a;
int b;
float c;
Initializing: To give a value to a variable is known as initializing a variable.
Eg.
char a;
a='Z';
int b;
b=2;
float c;
c=3.000000; (decimal is not neccesary while initializing, but when you will print a float variable , you will see the decimals)
CAN ALSO BE INITIALIZED THIS WAY:
char a='Z';
int b=2;
float c=3.000000;
Note: To initialize a char type of variable, you use ' ' single inverted commas, Eg. char a = 'Z';. This is what we have used in the if condition in the above example , if(op=='+');
When we write only the variable name like, (supposing int x = 10
printf("%d",x);
We will get 10 as output , that is the value of the varaible.
But when we write a variable name with ampersand(&), (supposing int x is located at 25834 on the memory)
printf("%d",&x);
We will get 25834 as output, as the &(ampersand) is a operator that tells the program to related the variable's address rather than its value.
Now you know why we write
scanf("%d",&a);
Rather than:
scanf("%d",a);
---------------------------------------------------------------------------------------------------------------------------------------------------------
Switch
---------------------------------------------------------------------------------------------------------------------------------------------------------------When we have to make only two decisions depending upon only TWO possibilities then we use If-Else.
Eg,
If the numbers are even then add them and if not , then subtract them
If the user is male then he have to pay 25.5% as tax from his income and if not male then 25.0% tax from her income
If a number less than 10 then multiply it by 100, if it is not less than 10 then divide it by 100, Etc.
But what if you want to make various decisions depending on various possibilities
Eg,
If the number is less than 10, then add 10. If the number is greater than 20 then subtract 10, if the number is 0 then add 20.
If the character entered by user is 'a' then print A, if 'b' then B,if 'c' then C, if'd' then D, if 'e' then E , Etc.
This is when you use switch case.
The Syntax of switch case is as follows:
Code:
[COLOR="DarkGreen"]Switch[/COLOR](CASE NUMBER)
[COLOR="DarkGreen"]Case [/COLOR]NUMBER 1:
{
CODES HERE;
}
[COLOR="DarkGreen"]Case [/COLOR]NUMBER 2:
{
CODES HERE;
}
[COLOR="DarkGreen"]Case [/COLOR]NUMBER 3:
{
CODES HERE;
}
[COLOR="DarkGreen"]Case [/COLOR]NUMBER 4:
{
CODES HERE;
}
Default:
{
CODES HERE;
}
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