Structure of C Program
Sunny Bhaskar
10/23/20241 min read
A C program is written in a specific structure, following certain rules and components to make it understandable and executable by the compiler. Here’s a breakdown of the basic structure of a C program:
1. Preprocessor Directives
These are the lines that begin with a `#`. They provide instructions to the compiler before the actual compilation starts.
The most common directive is `#include`, which is used to include header files.
Example
#include <stdio.h> // Includes the Standard Input Output header file
2. Global Declarations
Variables and function prototypes can be declared globally, meaning they can be used throughout the entire program.
Example
int globalVar; // Global variable
3. Main Function
Every C program must have a `main()` function. It’s the starting point of execution.
The main function can return an integer value (`int`), indicating success or failure of the program execution.
Example
int main() {
// Code inside main function
return 0; // Indicates that the program ended successfully
}
4. Variable Declaration
Inside the `main()` function, you can declare local variables that are used within the function.
Example
int a, b; // Declaring variables
5. Executable Statements
These are the actual C statements that perform operations, such as calculations, input/output, and function calls.
Example
a = 5;
b = 10;
int sum = a + b; // Executable statement
6. Input/Output Statements
Functions like `printf()` and `scanf()` are used for output and input operations.
Example
printf("The sum is: %d", sum); // Output
7. Return Statement
The `main()` function generally ends with a return statement, which returns a value to the operating system.
Returning `0` typically indicates that the program finished successfully.
Example
return 0;