Beginning with C programming

Beginning with C programming:
Finding a Compiler:

Before we start C programming, we need to have a compiler to compile and run our programs. There are certain online compilers like http://ideone.com/ or https://www.onlinegdb.com/online_c_compiler

that can be used to start C programming without installing a compiler.

Windows: There are many compilers available freely for compilation of C programs like Code Blocks and Dev-CPP.

Borland C(https://developerinsider.co/download-and-install-borland-c-compiler-on-windows-10/),

Turbo C (https://developerinsider.co/download-turbo-c-for-windows-7-8-8-1-and-windows-10-32-64-bit-full-screen/) etc


Linux: For Linux, gcc comes bundled with the linux, Code Blocks can also be used with Linux.

This Blog has been written based on Linux and all the given examples have been compiled on the Ubuntu flavor of the Linux system.If you are using Linux or UNIX, then check whether GCC is installed on your system by entering the following command from the command line

$ gcc -v

If you have GNU compiler installed on your machine, then it should print a message.
If GCC is not installed, then you will have to install it yourself using the detailed instructions available
at https://gcc.gnu.org/install/

Writing first program:
Following is first program in C
/* my first program */
#include <stdio.h>
int main(void)
{
printf("Hello World");
return 0;
}
Output:Hello World

Let us analyze the program line by line.

Line 0: [ /*my first program / ] In a C program, multi line comments are included between / * */. Comments are ingored by the compiler.Comments improve the readability and helps in documentation.It is a good practise to add commands at various sections of the program.Single line commands can also be added with //.

Line 1: [ #include <stdio.h> ] In a C program, all lines that start with # are processed by preprocessor which is a program invoked by the compiler. In a very basic term, preprocessor takes a C program and produces another C program. The produced program has no lines starting with #, all such lines are processed by the preprocessor. In the above example, preprocessor copies the preprocessed code of stdio.h to our file. The .h files are called header files in C. These header files generally contain declaration of functions. We need stdio.h for the function printf() used in the program.

Line 2 [ int main(void) ] There must to be starting point from where execution of compiled C program begins. In C, the execution typically begins with first line of main(). The void written in brackets indicates that the main doesn’t take any parameter . main() can be written to take parameters also. We will be covering that in future posts.

The int written before main indicates return type of main(). The value returned by main indicates status of program termination.

Line 3 and 6: [ { and } ] In C language, a pair of curly brackets define a scope and mainly used in functions and control statements like if, else, loops. All functions must start and end with curly brackets.

Line 4 [ printf(“Hello world”); ] printf() is a standard library function to print something on standard output. The semicolon at the end of printf indicates line termination. In C, semicolon is always used to indicate end of statement.

Compile and Execute C Program
Let us see how to save the source code in a file, and how to compile and run it. Following are the simple steps −Open a text editor and add the above-mentioned code.(vi,emac,gedit)

Save the file as hello.c

Open a command prompt and go to the directory where you have saved the file.

Type gcc hello.c and press enter to compile your code.

If there are no errors in your code, the command prompt will take you to the next line and would generate a.out executable file.

Now, type ./a.out to execute your program.

You will see the output "Hello World" printed on the screen.
$ gcc hello.c
$ ./a.out
Hello, World!

Make sure the gcc compiler is in your path and that you are running it in the directory containing the source file hello.c.