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


 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:


output:   hello

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

A simple C program to print “Hello”


  • 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.