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.