Basic Structure and Syntax of C Programming Language

🎯 Lab Objective

The objective of this lab is to:

• Understand the basic structure of a C program.
• Learn the role of header files, main function, and statements.
• Write, compile, and execute a simple C program.
• Get familiar with syntax rules such as semicolons, case-sensitivity, and indentation.

📖 Background

C is one of the most widely used programming languages, developed by Dennis Ritchie in the early 1970s at Bell Labs. It is the foundation of many modern languages (like C++, Java, and Python).

A C program typically contains:

1. Preprocessor directives (like #include)
2. Main function (int main())
3. Variable declarations
4. Statements for input/output, processing, and logic
5. Return statement to end the program

🧩 General Structure of a C Program

#include <stdio.h>    // Preprocessor directive

// Main function: program execution starts here
int main() {
    // Variable declaration
    int number;

    // Input from user
    printf("Enter a number: ");
    scanf("%d", &number);

    // Output
    printf("You entered: %d\n", number);

    return 0;   // Exit status
}

##🔎 Explanation of Each Part

1. Preprocessor Directives

Lines starting with # are instructions to the compiler before actual compilation.

Example:

#include <stdio.h>    

Includes the Standard Input Output library so that we can use printf() and scanf()

1. Main Function

Every C program must have main() Execution begins here:

int main() { ... } 

1. Variable Declarations

All variables must be declared before use. Example:

int number;

1. Input and Output

• Input:

  scanf("%d", &number);
  

• Output:

  printf("You entered: %d\n", number);
  

  1. Return Statement

Ends the program and returns control to the operating system:

return 0;

Syntax Rules in C

• Every statement must end with a semicolon (;).
• C is case-sensitive (main ≠ Main).
• Curly braces {} define the beginning and end of code blocks.
• Indentation and spacing are not mandatory, but they improve readability.