What are Data Types in C++?
In C++, data types tell the compiler what kind of value a variable can store. This helps the compiler know how much memory to allocate and what operations can be performed on that value.
For example, numbers can be used in mathematical calculations, but text (characters or strings) cannot be directly added to numbers. Using the correct data type avoids errors and gives correct results.
Example:
int age = 18; // Integer
float height = 5.6; // Float
double balance = 12345.67; // Double
char grade = 'A'; // Character
bool isPassed = true; // Boolean
Why Use Data Types?
- To efficiently use memory.
- To reduce errors in the program.
- To perform correct operations (like adding numbers or joining strings).
Types of Data Types in C++
C++ data types are mainly divided into three categories:
- Basic Data Types
- Derived Data Types (arrays, pointers, functions, references)
- User-defined Data Types (struct, class, enum, typedef, union)
1. Basic Data Types
These are the fundamental building blocks of C++ programs. They are used to represent simple values such as numbers, characters, and logical results.
Basic Data Types in C++:
- int – stores integers (whole numbers).
- float – stores decimal numbers (single precision).
- double – stores decimal numbers with double precision (more accurate).
- char – stores a single character.
- bool – stores logical values (
trueorfalse). - string – stores a sequence of characters (words or sentences).
- void – represents “no value” (used in functions with no return type).
Memory Size and Range of Basic Data Types
| Data Type | Size (in Bytes) | Range (Approximate) | Example |
|---|---|---|---|
| int | 4 | -2,147,483,648 to 2,147,483,647 | int age = 18; |
| float | 4 | ±3.4e−38 to ±3.4e+38 | float marks = 85.5; |
| double | 8 | ±1.7e−308 to ±1.7e+308 | double salary = 55000.75; |
| char | 1 | -128 to 127 | char grade = 'A'; |
| bool | 1 | true or false | bool isLogin = true; |
| string | Varies (1 byte per character) | No fixed range | string city = "Panipat"; |
| void | — | No data stored | void show(); |
Example of Basic Data Types
#include <iostream>
#include <string>
using namespace std;
int main() {
int rollNo = 101;
float percentage = 91.8;
double balance = 123456.789;
char grade = 'A';
bool isPassed = true;
string studentName = "Angel";
cout << "Student Name: " << studentName << endl;
cout << "Roll No: " << rollNo << endl;
cout << "Percentage: " << percentage << "%" << endl;
cout << "Bank Balance: " << balance << endl;
cout << "Grade: " << grade << endl;
cout << "Passed (1=True, 0=False): " << isPassed << endl;
return 0;
}Output:
Student Name: Angel
Roll No: 101
Percentage: 91.8%
Bank Balance: 123456.789
Grade: A
Passed (1=True, 0=False): 1
Explanation:
int→ stores whole numbers such as roll number.float→ stores percentage with decimals.double→ stores large decimal values with higher accuracy.char→ stores one character (like grade).bool→ stores result as true or false (pass/fail).string→ stores multiple characters like names or cities.
2. Derived Data Types (Overview)
These are data types derived from the basic types:
- Arrays – collection of elements of the same type.
- Pointers – store memory addresses of variables.
- Functions – blocks of code performing specific tasks.
- References – alternative names for existing variables.
Example:
int numbers[5] = {1, 2, 3, 4, 5}; // Array
int *ptr = &age; // Pointer
int &ref = age; // Reference
3. User-defined Data Types (Overview)
These are created by programmers to handle complex data. Examples include:
- struct – groups different data types together.
- class – used in Object-Oriented Programming (OOP).
- enum – defines a set of named constants.
- typedef/using – creates a new name for an existing type.
- union – similar to struct but shares same memory location.
Example:
struct Student {
int rollNo;
char name[50];
float marks;
};
enum Color {Red, Green, Blue};
typedef unsigned int uint;Summary:
- Data types define what type of data a variable will store.
- Basic types are the foundation; others are built using them.
- String is also a data type that stores text values.
- Size and range may vary depending on the compiler.
- Choosing the correct data type improves efficiency and accuracy.