# What is an Expression and What are the types of Expressions?

Expression: An expression is a combination of operators, constants and variables. An expression may consist of one or more operands, and zero or more operators to produce a value. Example:

```a+b
c
s-1/7*f
.
.
etc
```

Types of Expressions:

Expressions may be of the following types: • Constant expressions: Constant Expressions consists of only constant values. A constant value is one that doesn’t change.
Examples:

`5, 10 + 5 / 6.0, 'x’`
• Integral expressions: Integral Expressions are those which produce integer results after implementing all the automatic and explicit type conversions.
Examples:

`x, x * y, x + int( 5.0)`

where x and y are integer variables.

• Floating expressions: Float Expressions are which produce floating point results after implementing all the automatic and explicit type conversions.
Examples:

`x + y, 10.75`

where x and y are floating point variables.

• Relational expressions: Relational Expressions yield results of type bool which takes a value true or false. When arithmetic expressions are used on either side of a relational operator, they will be evaluated first and then the results compared. Relational expressions are also known as Boolean expressions.
Examples:

`x <= y, x + y > 2`
• Logical expressions: Logical Expressions combine two or more relational expressions and produces bool type results.
Examples:

` x > y && x == 10, x == 10 || y == 5 `
• Pointer expressions: Pointer Expressions produce address values.
Examples:

`&x, ptr, ptr++`

where x is a variable and ptr is a pointer.

• Bitwise expressions: Bitwise Expressions are used to manipulate data at bit level. They are basically used for testing or shifting bits.
Examples:

`x << 3`

shifts three bit position to left

`y >> 1`

shifts one bit position to right.

Shift operators are often used for multiplication and division by powers of two.

Note: An expression may also use combinations of the above expressions. Such expressions are known as compound expressions.

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