Lesson 2: C – Program Structure

C Hello World Example

Before we study Basic building blocks of the C programming language, ley us look a bare minimum C program structure so that we can take it as reference in upcoming chapters.

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!”:

Let us look various parts of the above program

1. The first line of thee program #include <stdio.h> is a preprocessor command, which tells a C compiler to include stdio.h file before going to actual compilation.
2. The next line int main() is the main function where program execution begins.
3. The next line /* my first program in C*/ 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.
4. The next line  printf(“Hello World!”) is another function available in C which causes the message “Hello World!” to be displayed on the screen.
5. 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, how to compile and run it. Following are the simple steps:

1. Open your C/C++ compiler¹ and add the above mentioned code.
2. Save the file as Hello World.c
3. Now Compile and run by clicking F9 (Code::Blocks).
4. If there are no errors in your code the compiler will create a windows which will display "Hello World!".

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