Basics of c programming

Basics of C Programming – A Beginner’s Guide

Welcome to the first article of this C programming series! Whether you're a student, a coding enthusiast, or preparing for technical interviews, understanding C lays a strong foundation for mastering any other language. This post is designed as a complete 1.5-hour lecture on the fundamentals of C programming.

🔰 Introduction to C Programming

Language: C is a procedural, general-purpose programming language developed by Dennis Ritchie in 1972.
Uses: Operating systems, embedded systems, compilers, games, system-level programming.
Why Learn C: It's fast, memory-efficient, and builds a solid base for other languages like C++, Java, and Python.

🧱 Structure of a C Program

#include <stdio.h>

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

#include <stdio.h> – Standard Input Output library.
main() – Entry point of any C program.
printf() – Prints output to the screen.
return 0; – Exits the program successfully.

💾 Variables, Data Types, and Constants

Variables store data values: int age = 21;
Data Types:

Data Type	Description	Example
int	Integer	`int a = 5;`
float	Decimal	`float pi = 3.14;`
char	Character	`char ch = 'A';`
double	Large decimal	`double d = 3.141592;`

Constants: const float PI = 3.14; – Value cannot change.

➕ Operators and Expressions

Operators perform operations on variables.

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

int x = 10, y = 20;
if (x < y && y > 0) {
    printf("Valid condition");
}

🔁 Control Structures

If-Else

if (a > b) {
    printf("A is greater");
} else {
    printf("B is greater");
}

Switch

switch(choice) {
    case 1: printf("Start"); break;
    case 2: printf("Stop"); break;
    default: printf("Invalid choice");
}

Loops

for (int i = 0; i < 5; i++) {
    printf("%d\n", i);
}

📥 Input and Output

Input:

scanf("%d", &num);

Output:

printf("Value is %d", num);

Common Format Specifiers:

%d – int
%f – float
%c – char
%s – string

🧪 Sample Program: 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\n", sum);
    return 0;
}

✅ Summary

C is a powerful, foundational language
Use main(), printf(), and scanf() for basic programs
Understand control flow: if, for, while
Use correct data types and operators

📝 Practice Problems

Write a program to check even or odd.
Write a program to find the maximum of three numbers.
Write a program to calculate the area of a circle.

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