A Simple C Program

A simple C program basically consists of the following parts −

Preprocessor Commands
Functions
Variables
Statements & Expressions
Comments

Basic structure of C program

#include

#include <stdio.h>
int main()
{
    /*  first C program */
    printf("Hello");
    return 0;
}

#include <stdio.h>

int main()

{

/* first C program */

printf("Hello");

return 0;

}

Above shown the basic structure of C program. For every program we have to write above mention basic structure.

How to write or print

We can write or print in C language by using printf() function. printf() function is a predefined function. for example: code to write “hello” is as follows:

printtf(“hello”);

output: hello

Note: any thing written within double code in a printf() function will be write.

A simple C program to print “Hello”

#include <stdio.h>
int main()
{
    /*  first C program */
    printf("Hello");
    return 0;
}

#include <stdio.h>

int main()

{

/* first C program */

printf("Hello");

return 0;

}

Description

First line #include <stdio.h> is a preprocessor, which instruct to C compiler to include stdio.h file. stdio.h (slandered input output ) is used for printf function.
int main() is the main function from where the program execution begins.
/*………..*/ is a “comments” in the program. This comments will be ignored by the compiler during execution of program
printf() is a predifned function in C which is used to print message.
line return 0; terminates the main() function and returns the value 0.return 0 tells the compiler that everything is ok and the execution of main() function ends. Because 0 is the code for successful execution, while values greater than 0 (integers) is an indication that something went wrong.

Compile and Execute C Program in Unix

How to save and compile the source code and run it:

Write the above-mentioned code on a text editor.
Save the file as hello.c
Open a command prompt and go to the directory where you have saved the file.
To compile your code: type gcc hello.c and press enter.
If there are no errors in your code, the command prompt will take you to the next line and generate a.out executable file.
To execute your program, type a.out and press enter.
Output “Hello” will print on the screen.

COMPILATION

$ gcc hello.c
$ ./a.out

1 2	$ gcc hello.c $ ./a.out

OUTPUT

Hello

Hello