C Programming Basics – A Beginner’s Guide

Introduction

C is one of the oldest and most powerful programming languages, created by Dennis Ritchie in 1972.
It is often called the “mother of programming languages” because many modern languages (C++, Java, Python) are influenced by it.

Why learn C?

It teaches programming fundamentals.
It is fast and efficient.
It gives you control over hardware.

Characteristics of C Language

Simple and structured – Easy to understand, programs are modular.
Portable – Same C program can run on different machines.
Middle-level language – Combines features of high-level (easy to code) and low-level (close to hardware).
Compiled language – Code is converted into machine code by a compiler.
Rich library – Provides many built-in functions.

Structure of a C Program

Every C program follows a standard structure:

#include <stdio.h>   // Header file

int main() {         // Main function
    printf("Hello, World!");  // Output statement
    return 0;        // Exit program
}

Explanation:

#include <stdio.h> → Header file that allows input/output functions.
int main() → Starting point of every C program.
printf() → Function to display output.
return 0; → Ends the program successfully.

Basic C Concepts

Variables and Data Types

Variables are used to store data. Each has a type.

int age = 20;          // Integer
float marks = 85.5;    // Decimal number
char grade = 'A';      // Character

Input and Output

Output: printf()
Input: scanf()

#include <stdio.h>

int main() {
    int age;
    printf("Enter your age: ");
    scanf("%d", &age);   // User input
    printf("You are %d years old", age);
    return 0;
}

Operators in C

Arithmetic: + - * / %
Relational: == != > < >= <=
Logical: && || !

Example:

int a = 10, b = 20;
printf("%d", a + b);  // Output: 30

Control Statements

If-Else

if(age >= 18) {
    printf("You can vote");
} else {
    printf("Not eligible to vote");
}

Switch

switch(day) {
  case 1: printf("Monday"); break;
  case 2: printf("Tuesday"); break;
  default: printf("Invalid day");
}

Loops in C

For Loop

for(int i = 1; i <= 5; i++) {
    printf("%d ", i);
}

Output: 1 2 3 4 5

While Loop

int i = 1;
while(i <= 5) {
    printf("%d ", i);
    i++;
}

Do-While Loop

int i = 1;
do {
    printf("%d ", i);
    i++;
} while(i <= 5);

Functions in C

Functions break programs into smaller parts.

#include <stdio.h>

void greet() {
    printf("Hello, welcome to C programming!");
}

int main() {
    greet();
    return 0;
}

Example Program – Find Sum of Two Numbers

#include <stdio.h>

int main() {
    int a, b, sum;
    printf("Enter two numbers: ");
    scanf("%d %d", &a, &b);
    sum = a + b;
    printf("Sum = %d", sum);
    return 0;
}

Input: 5 7
Output: Sum = 12

Advantages of C Programming

Fast execution
Portable across systems
Foundation for other languages
Powerful with memory management

Limitations of C

No built-in support for Object-Oriented Programming (OOP).
Manual memory management can be complex.
Programs can be error-prone without proper handling.

Quick Recap (Cheat Sheet)

C is the foundation language for programming.
Programs always start with #include <stdio.h> and main().
Variables store data (int, float, char).
Control structures: if-else, switch.
Loops: for, while, do-while.
Functions: help in modular programming.