Operators Precedence in C

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Operator precedence determines the grouping of terms in an expression. This affects how an expression is evaluated. Certain operators have higher precedence than others; for example, the multiplication operator has higher precedence than the addition operator.

For example x = 7 + 3 * 2; here, x is assigned 13, not 20 because operator * has higher precedence than +, so it first gets multiplied with 3*2 and then adds into 7.

Here, operators with the highest precedence appear at the top of the table, those with the lowest appear at the bottom. Within an expression, higher precedence operators will be evaluated first.

Category  Operator Associativity 
Postfix () [] -> . ++ - -   Left to right 
Unary  + - ! ~ ++ - - (type)* & sizeof  Right to left 
Multiplicative   * / % Left to right 
Additive  + -  Left to right 
Shift   << >>  Left to right 
Relational  < <= > >=  Left to right 
Equality   == !=  Left to right 
Bitwise AND  Left to right 
Bitwise XOR  Left to right 
Bitwise OR  Left to right 
Logical AND &&  Left to right 
Logical OR  ||  Left to right 
Conditional ?:  Right to left 
Assignment  = += -= *= /= %=>>= <<= &= ^= |= Right to left 
Comma  Left to right 

Example

Try the following example to understand the operator precedence available in C programming language:

#include <stdio.h>

main()
{
   int a = 20;
   int b = 10;
   int c = 15;
   int d = 5;
   int e;
 
   e = (a + b) * c / d;      // ( 30 * 15 ) / 5
   printf("Value of (a + b) * c / d is : %d\n",  e );

   e = ((a + b) * c) / d;    // (30 * 15 ) / 5
   printf("Value of ((a + b) * c) / d is  : %d\n" ,  e );

   e = (a + b) * (c / d);   // (30) * (15/5)
   printf("Value of (a + b) * (c / d) is  : %d\n",  e );

   e = a + (b * c) / d;     //  20 + (150/5)
   printf("Value of a + (b * c) / d is  : %d\n" ,  e );
  
   return 0;
}

When you compile and execute the above program it produces the following result:

Value of (a + b) * c / d is : 90
Value of ((a + b) * c) / d is  : 90
Value of (a + b) * (c / d) is  : 90
Value of a + (b * c) / d is  : 50


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