C Language Basics

Structure of a C Program

#include <stdio.h>

int main() {
    printf("Hello, World!");
    return 0;
}

Key Components

• #include <stdio.h> — Header file for input/output functions
• int main() — Main function where program execution begins
• printf() — Function to print output to the screen
• return 0; — Indicates successful program execution

Variables & Data Types

int age = 15;           // Integer
float marks = 85.5;     // Floating point
char grade = 'A';       // Single character

Common Data Types

Type	Size	Example
int	2/4 bytes	int a = 10;
float	4 bytes	float b = 5.5;
char	1 byte	char c = 'X';

Input & Output

int num;
printf("Enter a number: ");
scanf("%d", &num);
printf("You entered: %d", num);

• %d — Integer format specifier
• %f — Float format specifier
• %c — Character format specifier
• %s — String format specifier

Comments

// This is a single-line comment

/* This is a
   multi-line comment */

Exam Tips

• Always include stdio.h for input/output functions
• main() function is mandatory in every C program
• Use & before variable name in scanf()
• Every statement ends with a semicolon (;)

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