Skip to main content

Introduction to C Programming

Features of C Programming

  • C is a small language having lesser number of keywords than Java or pascal.
  • C is a native language of Unix, Linux. Not only that many of the windows packages, database programs, graphics libraries are written in C program
  • C is portable – it provides standard set of libraries that work on the same way with all machines
  • C is modular, as it supports functions to divide the program in to sub program
  • C is efficient on most machines, because certain constructs are machine dependant.

Structure of a C program

  • Comments
    • the comments are usually ignored by the compiler
    • so this part informs about the author of the program
    • what is the usefulness of this program
    • updation or creation of the program
    • Example: //  - Single line comment
    • /* ----- multi line comments    ….*/
  • Preprocessor Directives
    • before the compiler runs, the preprocessing takes place.
    • the preprocessors are prefix with a symbol #
    • Examples: #include, #define, #ifdef, #pragma, etc.
  • Function prototypes
    • This is to inform the compiler that the following functions are defined in this program.
    • it specifies the name of the function, arguments or parameters and return type and it ends with a semicolon
    • Ex: int sum(int,int);
  • Global Variables
    • Global variables which are declared above all the functions
    • As the name says, they are available to all the functions of that program
    • They are usually stored in the RAM
  • Main Function
    • main is the function which is main to the entire program
    • Every C program should have a main function
    • syntax: int main() { }
    • Earlier, the main program will return nothing, ie void, but now the compilers are instructing us to provide a return type for the main() function
  • User defined functions
    • After the main() function, the user defined functions are defined, as per the function prototype declared in the program
    • The function can be defined above the main function also, in that case there is not need for function prototype
    • Syntax:

int sum(int a, int b)

{

int f;

f=a+b;

return f;

}

Comments

Popular posts from this blog

Installation of NS2 (ns-2.35) in Ubuntu 20.04

Installation of NS2 (ns-2.35) in Ubuntu 20.04 LTS Step 1: Install the basic libraries like      $] sudo apt install build-essential autoconf automake libxmu-dev Step 2: install gcc-4.8 and g++-4.8 open the file using sudo mode $] sudo nano /etc/apt/sources.list Include the following line deb http://in.archive.ubuntu.com/ubuntu bionic main universe $] sudo apt update $] sudo apt install gcc-4.8 g++-4.8 Step 3:  Unzip the ns2 packages to home folder $] tar zxvf ns-allinone-2.35.tar.gz $] cd ns-allinone-2.35/ns-2.35 Modify the following make files. ~ns-2.35/Makefile.in Change @CC@ to gcc-4.8 change @CXX@ to g++-4.8 ~nam-1.15/Makefile.in ~xgraph-12.2/Makefile.in ~otcl-1.14/Makefile.in Change in all places  @CC@ to gcc-4.8 @CPP@ or @CXX@ to g++-4.8 open the file: ~ns-2.35/linkstate/ls.h Change at the Line no 137  void eraseAll() { erase(baseMap::begin(), baseMap::end()); } to This void eraseAll() { this->erase(baseMap::begin(), baseMap::end()); } All changes made Step 4: Open a new termi

Installing ns-3.34 in Ubuntu 20.04

This post shows how to install ns 3.34 in Ubuntu 20.04 LTS Prerequisites: Fresh installation of Ubuntu Version 20.04 LTS  ns3.34 can be downloaded from here Follow the video link for complete step by step instructions on the installation.  This version fixes the compilation issues of vanet-routing-compare.cc (bug in ns3.33)  Issue the following commands after opening a terminal  $ sudo apt update $ sudo apt install g++ python3 python3-dev python-dev pkg-config sqlite3 python3-setuptools git qt5-default gir1.2-goocanvas-2.0 python3-gi python3-gi-cairo python3-pygraphviz gir1.2-gtk-3.0 ipython3 openmpi-bin openmpi-common openmpi-doc libopenmpi-dev autoconf cvs bzr unrar openmpi-bin openmpi-common openmpi-doc libopenmpi-dev tcpdump wireshark libxml2 libxml2-dev Unzip or untar the ns-allinone-3.34.tar.bz2 in the home folder (in my case its /home/pradeepkumar) $ cd ns-allinone-3.34/ $ ./build.py --enable-examples --enable-tests  Once the installation is completed, you may get an output show

Installation of ns3 in Windows 10 and Windows 11 OS using WSL (Windows Subsystem for Linux)

This post shows how to install ns-3.33 in Windows 10 through WSL (Windows Subsystem for Linux) This posts works for Windows 11 also (I have tested it on a Windows 11 ISO and it works the Same way as mentioned in the following post.) This post will work for ns-3.3x version. Prerequisites : Install Windows Subsystem for Linux with GUI: Please refer the following video  System Information: OS used: Windows 10 and WSL (Ubuntu 20.04) GUI: XServer for Windows NS3 Version: ns-3.33 See the following complete video on how to install ns3 in Windows 10 Step 0 : Open XLaunch Step 1 :  Open WSL using PowerShell and open it as Administrator Command:/  wsl $ xfce4-session The GUI of Ubuntu Opens within Windows 10 OS. Step 2 : Download ns3 from nsnam.org website through Mozilla Firefox browser Step 3: Open a Terminal  $ sudo apt update $ sudo apt install build-essential autoconf automake libxmu-dev python3-pygraphviz cvs mercurial bzr git cmake p7zip-full python3-matplotlib python-tk python3-dev qt5-q