Rose Kamal Love

Rose Kamal Love

Variables, Literals and Datatypes in C++

Today we'll learn about variables, literals and constants in C++ with the help of examples

C++ Variable

In programming, a variable is a container (storage area) to hold data.

To indicate the storage area, each variable should be given a unique name (identifier). For example,

int age = 14;

Here, age is a variable of th int data type, and we have assigned an integer of value 14 to it

Note: The int data type suggests that the variable can only hold integers. Similarly, we can use the double data type if we have to store decimals and exponentials.

The value of a variable can be changed hence the name variable

int age = 14; // age is 14
age = 17; // age is now 17

Rules for naming a variable

  • A variable name can only have alphabets, numbers, and the underscore _.
  • A variable name cannot begin with a number.
  • It is a preferred practice to begin variable names with a lowercase character. For example, name is preferable to Name
  • A variable name cannot be a keyword. For example, int is a keyword that is used to denote integers.
  • A variable name can start with an underscore. However, it's not considered a good practice.

Note: We should try to give meaningful names to variables. For example, first_name is a better variable name than fn.

C++ Literal

Literals are data used for representing fixed values. They can be used directly in the code. For example: 1, 2.5, 'c' etc.

Here, 1, 2.5 and 'c' are literals. Why? You cannot assign different values to these terms.

Here's a list of different literals in C++ programming:

1. Integers

An integer is a numeric literal(associated with numbers) without any fractional or exponential part. There are three types of integer literals in C++ programming:

  • decimal (base 10) ( these two can be ignored for now )
  • octol (base 8)
  • hexadecimal (base 16)
Decimal: 0, -9, 22 etc
Octal: 021, 077, 033 etc
Hexadecimal: 0x7f, 0x2a, 0x521 etc

2. Floating Point Literals

A floating-point literal is a numeric literal that has either a fractional form or an exponent form. For example:

-2.0

0.0000234

-0.22E-5

3. Characters

A character literal is created by enclosing a single character inside single quotation marks. For example:

'a','m','F','2','}', etc

4. String Literals

A string literal is a sequence of characters enclosed in double-quote marks. For example:

"good" => string constant

"" => null string constant

" " => string contant of six white spaces

"x" => string constant having a single character

"Earth is round \n" => prints string with a newline

4. C++ Constants

In C++, we can create variables whose value cannot be changed. For that, we use the const keyword. Here's an example:

const int LIGHT_SPEED = 299792458;
LIGHT_SPEED = 2500 // Error! LIGHT_SPEED is a constant.

Here, we have used the keyword const to declare a constant named LIGHT_SPEED. If we try to change the value of LIGHT_SPEED, we will get an error.

C++ Data Types

In C++, data types are declarations for variables. This determines the type and size of data associated with variables. For example,

int age = 13;

Here, age is a variable of type int. Meaning, the variable can only store integers of either 2 or 4 bytes.

C++ Fundamental Data Types

  • int : Integer
  • float : Floating point (decimal)
  • double : Double Floatin-point
  • char : Charachter
  • bool : Boolean
  • void : Empty

Now, let us discuss these fundamental data types in more detail.

1. C++ int

  • The int keyword is used to indicate integers
  • Its size is usually 4 bytes. Meaning, it can store values from -2147483648 to 2147483647
  • For Example:
int salary = 85000;

2. float and double

  • float and double are used to store floating-point numbers (decimals and exponentials).
  • The size of float is 4 bytes and the size of double is 8 bytes. Hence, double has two times the precision of float. To learn more, visit C++ float and double.
  • For example,
float area = 64.74;
double volume = 134.64535;

As mentioned above, these two data types are also used for exponentials. For example,

double distance = 45E12    // 45E12 is equal to 45*10^12

3. C++ char

  • Keyword char is used for characters.
  • Its size is 1 byte.
  • Characters in C++ are enclosed inside single quotes ' '.
  • For example,
char test = 'h';

Note: In C++, an integer value is stored in a char variable rather than the character itself. To learn more, visit C++ charachters

5. C++ bool

  • The bool data type has one of two possible values: true or false.
  • Booleans are used in conditional statements and loops (which we will learn in later chapters).
  • For example,
bool cond = false;

C++ void

  • The void keyword indicates an absence of data. It means "nothing" or "no value".
  • We will use void when we learn about functions and pointers.

Note: We cannot declare variables of the void type.

Sourced from Programiz

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