Illustrate the basic structure of a C Programs and highlight usual sections of main function.

A C program is a set of instructions that tells the computer what to do. At the heart of every C program, there is a function called main(). This function is important because it's the starting point of any C program. When you run a C program, the execution begins from the main() function, and it ends when main() finishes executing.

Now, let's break down the typical structure of a C program and then focus on the sections inside the main() function:

1. Header Files: At the very top of a C program, we typically include header files. These files contain pre-written code that can be reused, like functions for input/output or mathematical operations. The most commonly used header file is #include , which allows us to use functions like printf() for output and scanf() for input.

2. Global Declarations: Below the header files, we can declare any global variables or constants. These variables can be used anywhere in the program.

3. Main Function: The main() function is the entry point for execution. It is where the program starts running. It typically contains the actual logic of the program—like variable declarations, function calls, loops, and conditionals.

4. Statements and Expressions: Inside the main() function, you'll have statements that define what the program should do. These could include assignments (a = 5;), condition checks (if statements), or loops (for, while loops).

5. Return Statement: Finally, the main() function typically ends with a return 0; statement. This tells the operating system that the program finished successfully.

Now let’s look at an example:

#include   // Header file for input/output functions

int main() {
    // Main function begins
    int a = 5, b = 10;  // Declaring variables
    printf("Sum: %d\n", a + b);  // Output: Sum of a and b
    return 0;  // Return statement indicating successful execution
}



Here, we have:

1. The #include  which is a header file.
2. The int main() function, where we declare the variables a and b.
3. We then print the sum of a and b using printf().
4. Finally, return 0; signals that the program ended successfully.