Introduction to C

What is Programming?

Programming is the process of creating instructions for a computer to perform specific tasks. It is done using programming languages like C, Python, Java, etc.

📌 Purpose:

• To solve problems efficiently
• Automate tasks
• Create applications, websites, games, software tools

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2. Introduction to C

C is a powerful, general-purpose programming language developed by Dennis Ritchie in 1972 at Bell Labs. It is widely used for system software, compilers, operating systems, and embedded systems.

🔑 Features:

• Procedural language
• Fast and efficient
• Portable and flexible
• Foundation of many modern languages (like C++, Java)

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3. Basic Syntax, Data Types, Variables

✅ Syntax:

Rules that define how C code should be written.

✅ Variables:

Containers to store data.

cCopyEditint age = 20;
float salary = 30000.50;
char grade = 'A';

✅ Data Types:

Type	Keyword	Example
Integer	int	int x = 10;
Decimal	float	float y = 5.5;
Character	char	char c = 'A';

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4. Input/Output (printf, scanf)

• printf() – Output function
• scanf() – Input function

📘 Example:

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

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5. Operators

✅ Types:

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

📘 Example:

cCopyEditint a = 5, b = 3;
printf("Sum: %d\n", a + b);           // 8
printf("Is a > b? %d\n", a > b);     // 1 (true)

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6. Conditional Statements

These help make decisions in code.

✅ if, else, else if, switch

📘 Example (if-else):

cCopyEditint age = 18;
if (age >= 18) {
    printf("You are an adult.");
} else {
    printf("You are a minor.");
}

📘 Example (switch):

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

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7. Loops

Used to execute code repeatedly.

✅ Types:

• for
• while
• do-while

📘 Example (for loop):

cCopyEditfor(int i = 1; i <= 5; i++) {
    printf("%d ", i);  // Output: 1 2 3 4 5
}

📘 Example (while loop):

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

📘 Example (do-while loop):

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

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8. Simple Programs

📘 1. Calculator (Add two numbers):

cCopyEdit#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;
}

📘 2. Area of a Circle:

cCopyEdit#include <stdio.h>
#define PI 3.14
int main() {
    float radius, area;
    printf("Enter radius: ");
    scanf("%f", &radius);
    area = PI * radius * radius;
    printf("Area = %.2f\n", area);
    return 0;
}

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✅ Summary Table

Topic	Description	Example Function
What is Programming?	Writing instructions for a computer	—
Introduction to C	Overview and features of C language	—
Syntax & Variables	Declaring & using variables	int x = 5;
Input/Output	Taking input, showing output	scanf, printf
Operators	Performing operations	+, >, &&
Conditional Statements	Making decisions	if, switch
Loops	Repeating code	for, while
Simple Programs	Basic coding tasks	calculator, area