Structure of a C Program

Definition:

A C program follows a structured format, which includes essential components like preprocessor directives, the main function, and statements.

#include <stdio.h>  // Preprocessor directive

// Main function: Entry point of every C program
int main() {
    printf("Hello, World!");  // Output statement
    return 0;  // Indicates successful execution
}

Structure Breakdown:

• #include <stdio.h>: Includes the standard input-output library.
• int main(): The main function where execution begins.
• printf("Hello, World!");: Prints output to the screen.
• return 0;: Indicates successful execution.

Data Types in C

Definition:

Data types in C define the type of data a variable can store. They determine the memory size and the operations that can be performed on the variable.

Variables and Constants

Variables

A variable is a named memory location that stores data and can be modified during program execution.

Syntax:

data_type variable_name = value;

Example:

int age = 25;
float height = 5.9;
char grade = 'A';

Constants

Constants are values that do not change during program execution.

Using const Keyword:

const float PI = 3.14159;

Using #define Macro:

#define PI 3.14159

Operators in C

Operators are symbols that perform operations on variables and values. They are classified into different types based on their functionality.

Arithmetic Operators

Relational Operators

Logical Operators

Bitwise Operators

5. Input and Output in C

Definition:

Input and output functions allow the program to interact with the user by receiving input and displaying output.

Output Functions

Example:

#include <stdio.h>
int main() {
    printf("Hello, World!\n");
    puts("Welcome to C Programming.");
    return 0;
}

Input Functions

Example (Using scanf()):

#include <stdio.h>
int main() {
    int age;
    printf("Enter your age: ");
    scanf("%d", &age);
    printf("You are %d years old.", age);
    return 0;
}

#include <stdio.h>
int main() {
    char name[30];
    printf("Enter your name: ");
    fgets(name, sizeof(name), stdin);  // Reads input safely
    printf("Hello, %s!", name);
    return 0;
}