Data Types

Big idea

The type says what kind of value a variable can hold.

The idea

Three types you'll use all the time:

Example

#include <stdio.h>

int main(void) {
    int count = 7;
    float price = 9.5;
    char grade = 'A';

    printf("%d\n", count);
    printf("%.2f\n", price);
    printf("%c\n", grade);
    return 0;
}

output
7
9.50
A

%.2f means "show 2 digits after the decimal point".

Watch it

Think of it like

Different containers for different things: a coin box for whole coins, a measuring cup for amounts like 9.5, and a name tag with room for just one letter.

🕷️ Spidey-sense: You wouldn't carry web fluid in a paper bag. A type is the right container for the job: int for whole numbers, float for decimals, char for a single letter. Pick the container first, then put things in.

Common mistake

A char uses single quotes. Double quotes are for text (strings).

char grade = "A";   // ✗
char grade = 'A';   // ✓

Key terms

• int — A whole number, like 7 or -3.
• float — A number with a decimal point, like 9.5.
• char — A single character, like 'A'.