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    C Tutorials

    Understanding a Simple C Program

    Introduction

    In this post, we will understand a simple C program to add two numbers and display the output of the sum. C program shown below:

    #include<stdio.h>
    
    /* Program to calculate
    
    * sum of Two numbers a,b
    
    */
    
    int main()
    
    {
    
    int a = 15; // Initialize a to 15.
    
    int b = 25; // Initialize b to 25.
    
    int sum = 0; // Initialize sum to 0.
    
    sum = a + b;
    
    printf("Sum is:%d", sum);
    
    return 0;
    
    }

     

    Preprocessor directive:

    #include<stdio.h> The #include statement is called a preprocessor directive. A preprocessor directive begins with a # sign. These statements are processed before compilation. The above directive tells the preprocessor to include the “stdio.h” header file to support standard I/O operations.  

     

    Comments:

    Comments are not executable statements. They are ignored by the compiler. Comments usually provide useful explanation and documentation of your programs to others. There are two kinds of comments:

     

    /* Program to calculate

    * sum of Two numbers a,b

    */

     

    Multi-line Comment begins with /* and ends with */. It may span more than one lines

     

    // Initialize a to 15.

    Single line comments begins with // and lasts until the end of the current line  

    main()

    int main() {

    …

    }

     

    The main() function is the entry point of program execution. main() is required to return an int (integer). Declaring variables a,b and sum. For example we have declared integer a to hold 15 using the below statement. int a = 15; Assigning the sum of two numbers a and b to sum variable.

    sum = a + b;

    printf(“…”);

    printf() function is used to print sum on to the console.

    printf(“Sum is:%d”, sum);

    return 0;

     

    This line is optional.C compiler will implicitly insert a “return 0;” to the end of the main() function. This statement terminates the main() function and returns a value of 0 to the operating system. Typically, return value of 0 signals normal termination; whereas value of non-zero signals abnormal termination.  

     

    The IDE used in the tutorial is Code:: Blocks. To download and install Code Blocks follow the link:

    https://www.testingdocs.com/download-and-install-codeblocks/

    For more information on Code Blocks IDE, visit the official website of Code blocks IDE: http://www.codeblocks.org/

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