4.1 Data Types in C++

A data type is a classification that tells the compiler:

1. What kind of value a variable can hold
2. How much memory to allocate
3. What operations can be performed on it

C++ provides several fundamental (primitive) data types built into the language.

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1. Integer Types (int)

Used to store whole numbers (no decimal part).

Signed vs Unsigned

• signed (default): stores both positive and negative values
• unsigned: stores only non-negative values (0 and above), doubling the positive range

int a = -10;           // signed (default)
unsigned int b = 200;  // unsigned, range: 0 to 4,294,967,295

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2. Floating-Point Types

Used to store real numbers (numbers with fractional/decimal parts).

float pi = 3.14f;
double precise_pi = 3.14159265358979;

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3. Character Type (char)

Used to store a single character using its ASCII code.

• Size: 1 byte (8 bits)
• Range: 0–255 (unsigned) or -128 to 127 (signed)
• Stores 256 possible values representing ASCII characters

char grade = 'A';   // stored as ASCII value 65
char newline = '\n'; // escape character

ASCII Examples:

• 'A' = 65, 'a' = 97, '0' = 48

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4. Boolean Type (bool)

Used to store logical values.

• Size: 1 byte
• Values: true (stored as 1) or false (stored as 0)

bool isLoggedIn = true;
bool hasError = false;

if (isLoggedIn) {
    cout << "Welcome!";
}

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5. Void Type (void)

void means no type or no value. It is used:

• As a return type for functions that return nothing
• For generic pointers (void*) that can point to any data type

void printMessage() {      // returns nothing
    cout << "Hello";
}

void *ptr1;    // generic pointer — can point to any type
int  *ptr2;    // typed pointer — can only point to int

void* vs int*

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Summary Table