Operators Precedence and Associativity in C Language

Introduction:

We have discussed about the Operators in C Programming language so far. But what if we have more than one operator in an expression. Then how to evaluate such kind of expressions. So to overcome this problem we have Operators Precedence and Associativity in C Language.

Operators Precedence and Associativity in C :

According to the language specification, Each and every Operator is given a precedence level. So Higher precedence operators are evaluated first after that the next priority or precedence level operators evaluated, so on until we reach finish the expression.

We have different precedence levels for different operators. and one precedence level can have multiple operators.

For example, Multiplication ( *), Division ( /) and Modulo division ( %) have the same precedence level.

So by using the Precedence of the Operators, We can decide which operator should be evaluated first, But what if we get the expression with more than one operator from the same precedence level?

If we get multiple operators from the Same precedence level, Then we use the Operators Associativity to determine which operation to do first.

If the Operators precedence is same, Then depending upon the operators associativity we will evaluate the expression. So Associativity is kind of tie-breaker (🎾) if Precedence is equal.

Operators Precedence and Associativity in C Table :

Level	Symbol	Description	Associativity
1	++ – – ( ) [ ] -> .	Prefix increment Prefix decrement Function call and subexpression Array subscript Structure pointer Structure member	left to right
2	! ~ – + (type) * & sizeof	Logical negation ( Logical NOT ) 1’s complement Unary negation Unary plus Type cast Pointer dereference Address of Operator Sizeof Operator	right to left
3	* / %	Multiplication Division Modulus (integer remainder)	left to right
4	+ –	Binary Addition Binary Subtraction	left to right
5	<< >>	Bitwise left shift Bitwise right shift	left to right
6	< <= > >=	Less than Less than or equal to Greater than Greater than or equal to	left to right
7	== !=	Equality Not equal	left to right
8	&	Bitwise AND	left to right
9	^	Bitwise exclusive OR (XOR)	left to right
10	|	Bitwise inclusive OR	left to right
11	&&	Logical AND	left to right
12	||	Logical inclusive OR	left to right
13	?:	Conditional Operator	right to left
14	= += -= *= /= %= <<= >>= &= ^= |	Assignment Compound Addition Compound subtraction Compound multiplication Compound division Compound modulus Compound bitwise left shift Compound bitwise right shift Compound bitwise AND Compound bitwise exclusive OR Compound bitwise OR	right to left
15	, ++ – –	Sequence point (list separator) Postfix increment Postfix decrement	left to right

Example to deministrate Operators Precedence and Associativity:

For example, If you have a expression like below.

10 * 40 / 20 % 6

Here we have three Operators, Multiplication * , Division / and Modulo Division %.

So according to above Precedence and Associativity table, We can see these three operators have the same precedence level. So we need to depend on the Associativity.

The associativity of multiplication, Division, and Modulo division operators is from left to right. So we need to evaluate the above expression from left to right.

The first operation will be,

10 * 40 result is 400 and expression became 400 / 20 % 6

Now we need to evaluate 400 / 20which is equal to 20.

The expression became 20 / 6 , The result of this expression is 2.

The final result is 2.

For the 10 * 40 / 20 % 6 Expression, We got the result as 2. So Let’s write a C Program to verify the result.

Example Program : Precedence and Associativity in C Language:

Output:

As you can see from the above output, The value of 10 * 40 / 20 % 6 Expression is 2.

So by using above Precedence and Associativity of Operators, We can evaluate any kind of complex expressions. If you are confused with difficult expressions, Please look at the Precedence and associativity table to evaluate expression.

Related Reading:

• Compilation Stages in C language.

• Structure of C Language.

• Arithmetic operators in C language.

• Identifiers in C language and Rules for naming Identifiers.