Define basic structure of C program ?

Here’s a breakdown of the basic structure of a C program, with explanations and a code example:

1. Preprocessor Directives:

• Lines starting with # that instruct the preprocessor to perform tasks before compilation.
• Common directives:
  • #include: Includes header files containing declarations and definitions.
  • #define: Defines macros for text substitution.

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

2. Main Function:

• The entry point of the program, where execution begins.
• It must return an integer value to signal program status.

int main() {
    // Code to be executed
    return 0; // Indicates successful termination
}

3. Variable Declarations:

• Informing the compiler about the variables used in the program and their data types.

int age = 25; // Declares an integer variable named age
char initial = 'A'; // Declares a character variable named initial

4. Statements:

• Instructions that perform actions or make decisions.
• Examples:
  • Assignment statements (x = y + 5;)
  • Conditional statements (if, else)
  • Loop statements (for, while)
  • Function calls (printf("Hello!");)

printf("Your age is %d.\n", age); // Print a message using printf

5. Comments:

• Non-executable text used for explanations and code clarity.
• Single-line comments: // This is a comment
• Multi-line comments: /* This is a multi-line comment */

6. Return Statement:

• Exits the main function and optionally returns a value to the operating system.

return 0; // Return 0 to indicate successful execution

Code Example:

#include <stdio.h>

int main() {
    int num1 = 10, num2 = 5;
    int sum = num1 + num2;

    printf("Sum of %d and %d is %d\n", num1, num2, sum);

    return 0;
}

Key Points:

• This structure forms a basic template for C programs.
• Indentation and spacing enhance readability.
• Comments are essential for code maintenance and understanding.
• Understanding this structure is crucial for writing well-structured and maintainable C programs.