Predefined Datatypes in C++

February 15, 2023

Predefined Datatypes

Here, we will discuss predefined data types in C++. There are various predefined datatypes in C++ and a program should at least be aware of them and what their uses are.

Definition It is a primary datatype that directly interacts with machine instructions

Datatypes describe what type of data is stored in the variables and describe the amount of memory required to be allocated for the data

1. Integer DataType

We will discuss the following –

Default int
Unsigned int
Long int
Unsigned long int
Short int
Unsigned short int

1. Default int

Description: It can accept a non-decimal value in both negative and positive ranges. Thus, the name integers.
Size: 2 or 4 bytes
Range: -32768 to +32768 or -2,147,483,648 to +2,147,483,648
Macros : (INT_MIN, INT_MAX)

Example:

int a = 10;
int b = -3512;

Note - Some compilers may support int as 2 bytes and some may support int as 4 bytes.

For 2 bytes range is: (-32,768, +32,767)
For 4 bytes range is : (-2,147,483,648, +2,147,483,648)

Most modern compiler support 4 bytes generally.

C++ Introduction

History of C++

Structure of a C++ Program

Program to check armstrong number or not

2. Unsigned int

Description: It can accept only positive values. A good use case for applications where only positive numbers are required example – Roll No., ticket system.
Size: 2 or 4 bytes
Range: 0 to +65,535 or 0 to +4,294,967,295
Macros : (USHRT_MAX)

Example:

unsigned int a = 10;
unsigned int b = 10987;

Note - Some compilers may support int as 2 bytes and some may support int as 4 bytes.

For 2 bytes range is: (0, +65,535)
For 4 bytes range is : (0, +4,294,967,295)

Most modern compiler support 4 bytes generally.

3. long int

Description: Ideal for very large integer values in positive/negative ranges.
Size: 4 or 8 bytes
Range: -2,147,483,648 to +2,147,483,647 or -9,223,372,036,854,775,808 to +9,223,372,036,854,775,807
Macros : (LONG_MIN, LONG_MAX)

Example:

long int a = 10172817;
long int b = -9876543210123;

Note - Some compilers may support int as 4 bytes and some may support int 8 bytes.

For 2 bytes range is: (-2,147,483,648 to +2,147,483,647)
For 4 bytes range is : (-9,223,372,036,854,775,808 to +9,223,372,036,854,775,807)

Most modern compiler support 8 bytes generally.
However, we can force 8 bytes guarantee if we use long long int instead of just long int

4. Unsigned long

Description: Ideal for very large integer values only in positive ranges.
Size: 4 or 8 bytes
Range: (0 to 4,294,967,295) or (0 to 18,446,744,073,709,551,615)
Macros : (ULONG_MAX)

Example:

long int a = 3120172817;
long int b = -9876512323443210123;

Note - Some compilers may support int as 4 bytes and some may support int 8 bytes.

For 2 bytes range is: (0 to 4,294,967,295)
For 4 bytes range is : (0 to 18,446,744,073,709,551,615)

Most modern compiler support 8 bytes generally.
However, we can force 8 bytes guarantee if we use unsigned long long int instead of just unsigned long int

5. Short

Description: Ideal for very small integer values in positive/negative ranges.
Size: 2 bytes guaranteed
Range: (-32,768 to 32,767)
Macros : (SHRT_MIN, SHRT_MAX)

Example:

long int a = 12;
long int b = -1087;

6. Unsigned short

Description: Ideal for very small integer values only in positive ranges.
Size: 2 bytes guaranteed
Range: (0 to 65,535)
Macros : (USHRT_MAX)

Example:

long int a = 1027;
long int b = 10;

2. Char DataType

We will discuss the following in this –

Default char
Unsigned char

1. Default char

Description: Every key in the keyboard acts as a char with an ASCII value. Characters are declared in the single quotation to distinguish them from variable names and character values
Size: 1 byte (8 bits)
Range: -128 to 127
Macros: CHAR_MAX and CHAR_MIN

Example

char a='@';
char b='c';

2. Unsigned char

Description: It accepts more number of characters than normal char type
Size: 1 bytes(8 bits)
Range : 0 to 255
Macro: UCHAR_MAX

Example

unsigned char a='ß'//beta charecter has ASCII value 223

3. float DataType

Description: It accepts fractional numbers up to 6 decimal place precision
Size: 4 bytes(32bits)
Macros : FLT_MAX and FLT_MIN

Range :

In positive range : +1.17549e-38 to +3.40282e+38
In negative range : -1.17549e-38 to -3.40282e+38

Note: 1.17549e-38 means 1.17549*10^(-38) which is very very small close to zero

Example

    float a = 56.771; 
    float b = 6.5;
    float c = 1.23e10; // 1.23 * 10^10
    float d = 1.98e-12;// 1.98 * 10^(-12)

4. Double DataType

Description: It accepts fractional numbers up to 12 decimal places mainly used for scientific computations
Size: 8 bytes(64 bits)
Macros: DBL_MAX and DBL_MIN

Range :

In positive range : +2.22507e-308 to +1.79769e+308
In negative range : -2.22507e-308 to -1.79769e+308

Note: 2.22507e-308 means 2.22507*10^(-308) which is very very small (close to zero).

Example

    // same numbers as float
    // but below have higher precision and higher range
    double a = 56.771; 
    double b = 6.5;
    double c = 1.23e10; // 1.23 * 10^10
    double d = 1.98e-12;// 1.98 * 10^(-12)

5. Long Double DataType

Description: It accepts fractional numbers up to 19 decimal places mainly used for scientific computations
Size: 16 bytes(128 bits)
Macros: LDBL_MAX and LDBL_MIN

Range :

In positive range : +3.3621e-4932 to +1.18973e+4932
In negative range : -3.3621e-4932 to -1.18973e+4932

Note: 3.3621e-4932 means 3.3621e *10^(4932) which is very very small (close to zero).

Example

    // same numbers as float/double
    // but below have higher precision and higher range
    long double a = 56.771; 
    long double b = 6.5;
    long double c = 1.23e10; // 1.23 * 10^10
    long double d = 1.98e-12;// 1.98 * 10^(-12)

6. wchar_t DataType

Description: Wide char can take on 65536 values which correspond to UNICODE values which is a recent international standard that allows for the encoding of characters for virtually all languages and commonly used symbols.
Size: 16 bytes(128 bits)
Range :0 to 65,535 or 4294967296

Mostly the wchar_t data type is used when international languages like Chinese, French are used.

Example

wchar_t b = L'艾儿';//Chinese alphabet

7. bool DataType

The ISO/ANSI C++ Standard has added certain new data types to the original C++ specifications.
They are provided to provide better control in certain situations as well as for providing conveniences to C++ programmers.

Syntax:

bool b = true; // declaring a boolean variable with true value

In C++, the data type bool has been introduced to hold a boolean value, true or false.
The values true or false have been added as keywords in the C++ language.

Note:

The default numeric value of true is 1 and false is 0.
We can use bool type variables or values true and false in mathematical expressions also.

Example

int x = false + true + 5;//6

The above expression is valid and the expression on the right will evaluate to 6 as false has value 0 and true will have value 1.
It is also possible to convert implicitly the data type integers or floating-point values to bool type.

Example:-

bool x = 0; // false 
bool y = 100; // true 
bool z = 18.75; // true

C++ program demonstrating predefined datatypes

Run

#include<iostream>
using namespace std;

int main()
{
    int a = 567; //valid  
    int b = 2147483800; //invalid : will result in loss of precison max int value 2147483647
    long long int c = 2147483800; // valid because of enough size max long int value 9,223,372,036,854,775,807
    char d ='_'; //underscorecharecter
    double e = 66.91;
    bool f= false;
    bool g= true;
  
    cout << "a:" << a << endl;
    cout << "b:" << b << endl; // incorrect value will be printed due to overflow
    cout << "c:" << c << endl;
    cout << "d:" << d << endl; 
    cout << "e:" << e << endl;
    cout << "f:" << f << endl;
    cout << "g:" << g << endl;
    
    return 0;
}

Output

a:567
b:-2147483496
c:2147483800
d:_
e:66.91
f:0
g:1

Important Points

Rage of datatypes always in between -2^n-1to 2^n-1-1 and 0 to 2ⁿ -1 for unsigned types, where n is the number of bits

Example:

int: -2¹⁵ to 2¹⁵-1 i.e -128 to 127
unsigned int: 0 to 2¹⁶-1 i.e 0 to 65535

2. -ve numbers are always stored in,2’s compliment form hence you can allocate with +1 in the maximum negative range

Example:

-32768,-128 etc

Prime Course Trailer

Related Banners

Get PrepInsta Prime & get Access to all 200+ courses offered by PrepInsta in One Subscription

Get over 200+ course One Subscription

Courses like AI/ML, Cloud Computing, Ethical Hacking, C, C++, Java, Python, DSA (All Languages), Competitive Coding (All Languages), TCS, Infosys, Wipro, Amazon, DBMS, SQL and others

Checkout list of all the video courses in PrepInsta Prime Subscription

One comment on “Predefined Datatypes in C++”

pardha saradhi lokarapu
Learning is good for beginners.

2

Log in to Reply