Basic data types

Introduction

Basic data types help us tell the computer what kind of information we want to store, like numbers or letters.

When you want to store whole numbers like age or count.

When you need to store decimal numbers like price or temperature.

When you want to store a single character like a letter or symbol.

When you want to store true or false values.

When you want to store text using arrays of characters.

Syntax

C

int myNumber;
float myDecimal;
char myLetter;
bool myFlag;  // requires #include <stdbool.h>

int stores whole numbers.

float stores decimal numbers.

char stores a single character.

bool stores true or false values (needs #include <stdbool.h>).

Examples

Stores the whole number 25 in a variable named age.

C

int age = 25;

Stores the decimal number 19.99 in price.

C

float price = 19.99;

Stores the letter 'A' in grade. Note the single quotes for characters.

C

char grade = 'A';

Stores a true/false value in isOpen. You must include stdbool.h to use bool.

C

#include <stdbool.h>
bool isOpen = true;

Sample Program

This program shows how to use basic data types in C. It prints each value with a message.

C

#include <stdio.h>
#include <stdbool.h>

int main() {
    int age = 30;
    float temperature = 36.6f;
    char initial = 'J';
    bool isSunny = true;

    printf("Age: %d\n", age);
    printf("Temperature: %.1f\n", temperature);
    printf("Initial: %c\n", initial);
    printf("Is it sunny? %s\n", isSunny ? "Yes" : "No");

    return 0;
}

Important Notes

Remember to use single quotes for char values, like 'A'.

Use %d in printf for int, %f for float, and %c for char.

Boolean values print as 1 (true) or 0 (false) by default, so use a conditional to print words.

Summary

Basic data types store different kinds of simple information.

int for whole numbers, float for decimals, char for single characters, and bool for true/false.

Use the right type to help the computer understand your data.

Practice

1. Which C data type is used to store whole numbers without decimals?

easy

A. int

B. float

C. char

D. bool

Solution

1. Step 1: Understand data types for numbers

   Whole numbers without decimals are stored using the int type in C.

2. Step 2: Identify correct type for whole numbers

   float stores decimals, char stores characters, and bool stores true/false values.

3. Final Answer:

   int -> Option A

4. Quick Check:

   Whole numbers = int [OK]

Hint: Whole numbers use int type in C [OK]

Common Mistakes:

• Confusing float with int for whole numbers
• Using char for numbers
• Thinking bool stores numbers

2. Which of the following is the correct way to declare a variable of type float in C?

easy

A. int number = 3.14;

B. char number = 3.14;

C. float number = 3.14;

D. bool number = 3.14;

Solution

1. Step 1: Check variable declaration syntax

   In C, to declare a float variable, use the keyword float followed by the variable name and value.

2. Step 2: Match type with value

   Assigning 3.14 (a decimal) to a float variable is correct. Other types like int, char, or bool cannot hold decimal values properly.

3. Final Answer:

   float number = 3.14; -> Option C

4. Quick Check:

   Decimal numbers use float type [OK]

Hint: Use float keyword for decimal numbers [OK]

Common Mistakes:

• Using int for decimal values
• Assigning decimal to char
• Using bool for numbers

3. What will be the output of this C code?

char letter = 'A';
int number = 5;
float decimal = 3.5;
printf("%c %d %.1f", letter, number, decimal);

medium

A. A 5 3

B. 65 5 3.5

C. A 5 3.50

D. A 5 3.5

Solution

1. Step 1: Understand format specifiers

   %c prints a character, %d prints an integer, and %.1f prints a float with one decimal place.

2. Step 2: Match variables to specifiers

   letter = 'A' prints 'A', number = 5 prints 5, and decimal = 3.5 prints 3.5 with one decimal.

3. Final Answer:

   A 5 3.5 -> Option D

4. Quick Check:

   Format specifiers match output [OK]

Hint: Match %c, %d, %.1f to char, int, float [OK]

Common Mistakes:

• Printing char as int (shows ASCII code)
• Ignoring decimal precision
• Confusing format specifiers

4. Identify the error in this C code snippet:

bool flag = 1;
char letter = "B";
int count = 10;

medium

A. char should use single quotes for characters

B. bool cannot be assigned 1

C. int cannot be assigned 10

D. No errors, code is correct

Solution

1. Step 1: Check bool assignment

   Assigning 1 to bool is allowed since 1 means true in C.

2. Step 2: Check char assignment

   Characters must be in single quotes ('B'), not double quotes ("B") which are for strings.

3. Final Answer:

   char should use single quotes for characters -> Option A

4. Quick Check:

   char uses single quotes [OK]

Hint: Use single quotes for char, double for strings [OK]

Common Mistakes:

• Using double quotes for char
• Thinking bool can't be 1 or 0
• Confusing int assignments

5. You want to store a student's grade as a letter (A, B, C, etc.) and whether they passed (true/false). Which data types should you use in C?

hard

A. int for grade, float for pass status

B. char for grade, bool for pass status

C. float for grade, int for pass status

D. bool for grade, char for pass status

Solution

1. Step 1: Choose type for grade letter

   Grade letters like 'A' are single characters, so char is the right type.

2. Step 2: Choose type for pass status

   Pass/fail is a true/false value, so bool fits perfectly.

3. Final Answer:

   char for grade, bool for pass status -> Option B

4. Quick Check:

   Letter = char, true/false = bool [OK]

Hint: Use char for letters, bool for true/false [OK]

Common Mistakes:

• Using int or float for letter grades
• Using char for true/false values
• Mixing data types incorrectly