C Operators , precedence and Expressions

C – Operators and Expressions

• The symbols which are used to perform logical and mathematical operations in a C program are called C operators.
• These C operators join individual constants and variables to form expressions.
• Operators, functions, constants and variables are combined together to form expressions.
• Consider the expression A + B * 5. where, +, * are operators, A, B are variables, 5 is constant and A + B * 5 is an expression.

Types of C operators:

C language offers many types of operators. They are,

Types of Operators	Description
Arithmetic operators	These are used to perform mathematical calculations like addition, subtraction, multiplication, division and modulus
Assignmentoperators	These are used to assign the values for the variables in C programs.
Relational operators	These operators are used to compare the value of two variables.
Logical operators	These operators are used to perform logical operations on the given two variables.
Bit wise operators	These operators are used to perform bit operations on given two variables.
Conditional (ternary) operators	Conditional operators return one value if condition is true and returns another value is condition is false.
Increment/decrement operators	These operators are used to either increase or decrease the value of the variable by one.
Special operators	&, *, sizeof( ) and ternary operators.

Arithmetic Operators in C:

C Arithmetic operators are used to perform mathematical calculations like addition, subtraction, multiplication, division and modulus in C programs.

Arithmetic Operators/Operation	Example
+ (Addition)	A+B
– (Subtraction)	A-B
* (multiplication)	A*B
/ (Division)	A/B
% (Modulus)	A%B

Assignment operators in C:

• In C programs, values for the variables are assigned using assignment operators.
• For example, if the value “10” is to be assigned for the variable “sum”, it can be assigned as “sum = 10;”
• There are 2 categories of assignment operators in C language. They are,
  1.Simple assignment operator ( Example: = )
  2. Compound assignment operators ( Example:+=, -=, *=, /=, %=, &=, ^= )

Operators	Example/Description
=	sum = 10; 10 is assigned to variable sum
+=	sum += 10; This is same as sum = sum + 10
-=	sum -= 10; This is same as sum = sum – 10
*=	sum *= 10; This is same as sum = sum * 10
/=	sum /= 10; This is same as sum = sum / 10
%=	sum %= 10; This is same as sum = sum % 10
&=	sum&=10; This is same as sum = sum & 10
^=	sum ^= 10; This is same as sum = sum ^ 10

Relational operators in C:

Relational operators are used to find the relation between two variables. i.e. to compare the values of two variables in a C program.

Operators	Example/Description
>	x > y (x is greater than y)
<	x < y (x is less than y)
>=	x >= y (x is greater than or equal to y)
<=	x <= y (x is less than or equal to y)
==	x == y (x is equal to y)
!=	x != y (x is not equal to y)

Logical operators in C:

• These operators are used to perform logical operations on the given expressions.
• There are 3 logical operators in C language. They are, logical AND (&&), logical OR (||) and logical NOT (!).

Operators	Example/Description
&& (logical AND)	(x>5)&&(y<5) It returns true when both conditions are true
|| (logical OR)	(x>=10)||(y>=10) It returns true when at-least one of the condition is true
! (logical NOT)	!((x>5)&&(y<5)) It reverses the state of the operand “((x>5) && (y<5))” If “((x>5) && (y<5))” is true, logical NOT operator makes it false

Bit wise operators in C:

• These operators are used to perform bit operations. Decimal values are converted into binary values which are the sequence of bits and bit wise operators work on these bits.

Below are the bit-wise operators in C language.

• & – Bitwise AND
• | – Bitwise OR
• ~ – Bitwise NOT
• ^ – XOR
• << – Left Shift
• >> – Right Shift

Truth table for bit wise operations ( OR, AND, EX-OR)

Conditional or ternary operators in C:

• Conditional operators return one value if condition is true and returns another value is condition is false.
• This operator is also called as ternary operator.

Syntax : (Condition? true_value: false_value);

Example : (A > 100 ? 0 : 1);

• In above example, if A is greater than 100, 0 is returned else 1 is returned.This is equal to if else conditional statements.

Example: ( university question)

Write a program for evaluating the function Y using ternary operator.

Y=1 x >5

Y=0 x <=5

#include <stdio.h>

int main()

{

    int x=6;

    int Y=(x>5)?1:0;

    printf("%d",Y);

}

Increment/decrement operators in C:

• Increment operators are used to increase the value of the variable by one and decrement operators are used to decrease the value of the variable by one in C programs.
• Syntax:
  Increment operator: ++var_name; (or) var_name++;
  Decrement operator: – -var_name; (or) var_name – -;
• Example:
  Increment operator :++ i ; i ++ ;
  Decrement operator : – – i ; i – – ;

Special Operators in C:

Below are some of the special operators that the C programming language offers.

Operators	Description
&	This is used to get the address of the variable. Example : &a will give address of a.
*	This is used as pointer to a variable. Example : * a where, * is pointer to the variable a.
sizeof ()	This gives the size of the variable. Example : sizeof (char) will give us 1.

Operator Precedence:

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

For example, x = 7 + 3 * 2; here, x is assigned 13, not 20 because operator * has a 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.

Precedence	Operator	Description	Associativity
1	++ --	Suffix/postfix increment and decrement	Left-to-right
	()	Function call
	[]	Array subscripting
	.	Structure and union member access
	->	Structure and union member access through pointer
	(type){list}	Compound literal(C99)
2	++ --	Prefix increment and decrement	Right-to-left
	+ -	Unary plus and minus
	! ~	Logical NOT and bitwise NOT
	(type)	Type cast
	*	Indirection (dereference)
	&	Address-of
	sizeof	Size-of[note 1]
	_Alignof	Alignment requirement(C11)
3	* / %	Multiplication, division, and remainder	Left-to-right
4	+ -	Addition and subtraction
5	<< >>	Bitwise left shift and right shift
6	< <=	For relational operators < and ≤ respectively
	> >=	For relational operators > and ≥ respectively
7	== !=	For relational = and ≠ respectively
8	&	Bitwise AND
9	^	Bitwise XOR (exclusive or)
10	|	Bitwise OR (inclusive or)
11	&&	Logical AND
12	||	Logical OR
13	?:	Ternary conditional	Right-to-Left
14	=	Simple assignment
	+= -=	Assignment by sum and difference
	*= /= %=	Assignment by product, quotient, and remainder
	<<= >>=	Assignment by bitwise left shift and right shift
	&= ^= |=	Assignment by bitwise AND, XOR, and OR
15	,	Comma	Left-to-right

Example:

#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;
}

Output:

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

Largest among 3 numbers using ternary(conditional) operator (university question)
#include <stdio.h>
int main ()
{
    int a,b,c,larg;
    printf("Enter the three numbers.... !\n");
    scanf("%d%d%d",&a,&b,&c);
    larg=a>b?(a>c?a:c):(b>c?b:c);
    printf("Largest=%d\n",larg);
}

Output:

Enter the three numbers.... !

2 3 5

Largest=5