C Hello World Example

C Hello World Example

A C program basically consists of the following parts:

• Preprocessor Commands
• Functions
• Variables
• Statements & Expressions
• Comments

Let us look at a simple code that would print the words "Hello World":

#include <stdio.h>

int main()
{
   /* my first program in C */
   printf("Hello, World! \n");
   
   return 0;
}

Let us look various parts of the above program:

• The first line of the program #include is a preprocessor command which tells a C compiler to include stdio.h file before going to actual compilation.
• The next line int main() is the main function where program execution begins.
• The next line /*...*/ will be ignored by the compiler and it has been put to add additional comments in the program. So such lines are called comments in the program.
• The next line printf(...) is another function available in C which causes the message "Hello, World!" to be displayed on the screen.
• The next line return 0; terminates main()function and returns the value 0.

Compile & Execute C Program:Lets look at 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.
• Save the file as hello.c
• Open a command prompt and go to the directory where you 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 be able to see "Hello World" printed on the screen

$ gcc hello.c
$ ./a.out
Hello, World!

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