Chapter 3: Variables, Data Types, and I/O

Table of Contents

• Table of Contents
• 3.1 Variables in C
• 3.2 Data Types
• 3.3 Input and Output
• 3.4 Exercises
• 3.5 Solutions
  • 3.5.1 Solution 1
  • 3.5.2 Solution 2
  • 3.5.3 Solution 3
• 3.6 What’s Coming in the Next Chapter

3.1 Variables in C

Variables are used to store data. In C, you must declare a variable before using it. Example:

int age;
double salary;

3.2 Data Types

C provides several basic data types:

• int for integers
• float for floating-point numbers
• double for double-precision floating-point numbers
• char for characters

Example:

int count = 10;
float price = 5.99;
char letter = 'A';

3.3 Input and Output

Use scanf for input and printf for output:

#include <stdio.h>

int main() {
    int number;
    printf("Enter a number: ");
    scanf("%d", &number);
    printf("You entered: %d\n", number);
    return 0;
}

3.4 Exercises

1. Declare an integer variable and assign it a value.
2. Write a program to read a float from the user and print it.
3. What is the difference between float and double?

3.5 Solutions

3.5.1 Solution 1

int x = 5;

3.5.2 Solution 2

#include <stdio.h>
int main() {
    float f;
    printf("Enter a float: ");
    scanf("%f", &f);
    printf("You entered: %f\n", f);
    return 0;
}

3.5.3 Solution 3

float is single precision, double is double precision (more accurate, uses more memory).

3.6 What’s Coming in the Next Chapter

Next, you’ll learn about control flow in C: if, else, and loops!

Next Chapter → Control Flow – if, else, and Loops