Precedence and Associativity of Operators in C

January 17, 2023

Precedence and Associativity:

On this page we will discuss about the Precedence and associativity of operators in C language.Precedence of operator comes into picture when in an expression we need to decide which operator will be executed first.Operator with higher precedence will be executed first.If the operators have same precedence in that case associativity comes into play.

Precedence and Associativity of Operators in C Language:

Precedence of Operators – Suppose, you have multiple operators in an expression.Then which operator will be evaluated first is decided by the precedence.Operator with higher precedence will be evaluated first.

For Example:

NOTE: Precedence of multiplication is greater than addition.

Therefore, 4+(5*6)= 34 is correct.Whereas,(4+5)*6=54 is wrong.Because precedence of (5*6) is greater so it will be evaluated first then the addition will ne performed.Hence the final answer is 34 and not 54.

Conditional Statement in C

Associativity of Operators – Associativity of operators come into picture when precedence of operators are same and we need to decide which operator will be evaluated first.Associativity can be either left to right(LTR) or right to left(RTL).

For Example:

NOTE: Since the precedence of multiplication is same in this case associativity comes into picture.The associativity of multiplication and division is from left to right.

Therefore,(20/4)*10=50 is correct and the 20/(4*10)=1/2 is wrong .Because the associativity of division amd multiplication is from left to right.So, division will be performed first then multiplication.

CATEGORY	OPERATORS	Suggested Avg. Time
Parenthesis/brackets	( ) [ ] -> . ++ —	Left to Right
Unary	! ~ ++ — + – * & (type) sizeof	Right to Left
Multiplicative	* / %	Left to Right
Additive	+ –	Left to Right
Bitwise Shift	<< >>	Left to Right
Relational	< <= > >=	Left to Right
Equality	== !=	Left to Right
Bitwise AND	&	Left to Right
Bitwise XOR	^	Left to Right

NOTE: The associativity will not come into picture when we have just one operator and which function will be called is undefined.Associativity will only work when we have more than one operators of same precedence.

Lets see an example:

Run

#include<stdio.h> 
int prep ()
{
  printf ("Prep");
  return 1;
}

int insta ()
{
  printf ("Insta");
  return 1;
}

int main ()
{
  int p;
  p = prep () + insta ();
  printf ("%d", p);
  return 0;
}

Output:

PrepInsta2

Which function is called first? prep() or inst()?

Well according to above output prep( ) is called first but it is not defined whether prep( ) will be called first or whether insta( ) will be called.Behaviour is undefined and output is compiler dependent.

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