Operators in C Programming : Relational and Logical Operators

Relational Operators are those that are used to compare two similar operands, and depending on their relation take some actions. The relational operators in C are listed as

Operators                   Meaning

<                                  less than

<=                                less than or equal to

>                                  greater than

>=                                greater than or equal to

= =                               Equality equal to

! =                                Operators not equal to

These operators all fall within the same precedence group, which is lower than the arithmetic and unary operators. The associativity of these operators is left to right.

# Suppose that i, j and k are integer variables whose values are 1, 2 and 3 respectively. Several relational expressions involving these variables:

Expressions                Interpretation                        Value

i < j                              true                                          1

(i+j) >= k                    true                                         1

(j+k) > (i+5)                false                                        0

k! = 3                           false                                         0

j = = 2                          true                                          2

In addition to the relational and equality operators, is used to assign a value to an identifier, where as the equality operator is used to determine if two expressions have the same value. These operators cannot be used in place of one another.

Assignment expressions are often referred as assignment statements.

Multiple assignments of the form are permissible as

identifier1 = identifier2 = - - - - - - - = identifier n

In such situation, the assignments are carried out from right to left.

Multiple assignment

identifier1 = identifier = expression.

is equivalent to

identifier1 = (identifier2 = expression)

And so on, with right to left resting for additional multiple assignments. C contains the following five additional assignment operators:

+ = ,   - = ,    * = ,    / =   and    % =

They are also k/shorthand assignment operators.

expression1 + = expression2

Is equivalent to:

expression1 = expression 1 + expression

Expression Equivalent Expression

a + = b a = a+b

a - = b a = a-b

a * = b a = a*b

a / = b a = a/b

a% = b a = a%b

The general form of shorthand assignment operators

variable1 operator = variable2 (or expression)

The use of shorthand assignment operator has three advantages:

1. What appears on the left-hand side need not be repeated and therefore it becomes easier to write.

2. The statement is more concise and easier to read.

3. The statement is more efficient.