In the previous tutorial you learnt about C++ comments. Now, let's learn about variables, constants and literals in C++.
C++ Variables
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 the int data type, and we have assigned an integer value 14 to it.
The value of a variable can be changed, hence the name variable.
int age = 14; // age is 14
age = 17; // age is 17
Visit this page to learn more about different types of data a variable can store.
- 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,
intis 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++ 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.
A constant can also be created using the #define preprocessor directive. We will learn about it in detail in the C++ Macros tutorial.
C++ Literals
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.
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)
- octal (base 8)
- hexadecimal (base 16)
For example:
Decimal: 0, -9, 22 etc
Octal: 021, 077, 033 etc
Hexadecimal: 0x7f, 0x2a, 0x521 etc
In C++ programming, octal starts with a 0, and hexadecimal starts with a 0x.
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
Note: E-5 = 10-5
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 constant of six white space |
"x" |
string constant having a single character |
"Earth is round\n" |
prints string with a newline |
We will learn about strings in detail in the C++ string tutorial.