Basics of C language syntax and structure

Here’s a simple example demonstrating the basic syntax and structure of a C program. This program takes two integers from the user, adds them, and displays the result:

#include <stdio.h>  // Include standard input/output library

int main() {        // Main function: entry point of the program
    int num1, num2; // Declare two integer variables
    int sum;        // Declare an integer to hold the result

    // Prompt the user to enter two integers
    printf("Enter first integer: ");
    scanf("%d", &num1);  // Read first integer from user and store in num1

    printf("Enter second integer: ");
    scanf("%d", &num2);  // Read second integer from user and store in num2

    sum = num1 + num2;   // Add the two numbers and store the result in sum

    // Display the result
    printf("The sum of %d and %d is: %d\n", num1, num2, sum);

    return 0;  // Return 0 to indicate successful execution
}

Explanation of Code Structure and Syntax

1. Preprocessor Directive (#include <stdio.h>)

• #include <stdio.h> is a preprocessor directive that includes the standard input/output library, which provides functions like printf and scanf for displaying text and receiving input from the user.
• Directives starting with # are processed before compilation begins, allowing for library and macro inclusion.

2. Main Function (int main())

• The main function is the entry point for every C program. The execution of a program starts from this function.
• It returns an integer value (int) to the operating system, which traditionally indicates success or failure. return 0; at the end signals that the program ran successfully.

3. Variable Declarations

• int num1, num2; declares two integer variables, num1 and num2, which will hold the input values.
• int sum; declares another integer variable, sum, to store the result of the addition.

4. Input and Output

• printf("Enter first integer: "); prints a message prompting the user to input a value.
• scanf("%d", &num1); reads an integer from user input and stores it in num1. The %d format specifier tells scanf to expect an integer, and &num1 is the address of the variable where the input is stored.
• The same steps are repeated for num2.

5. Computation

• sum = num1 + num2; performs the addition of num1 and num2 and stores the result in the sum variable.

6. Displaying Results

• printf("The sum of %d and %d is: %d\n", num1, num2, sum); outputs the result.
• The format specifier %d is used to insert the values of num1, num2, and sum into the string, replacing each %d with the corresponding value.
• \n is a newline character, which moves the cursor to a new line after printing.

7. Return Statement

• return 0; ends the program, signaling that it finished successfully.