# 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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