1 C Programming Reference Note

Unit-4
Operators and Expression
Operators
- An operator is a symbol that operates on single or multiple data items.
- Used in program to perform certain mathematical or logical manipulations.
E.g. In a simple expression 2+3, the symbol “+” is called an operator which operates on
two data items 2 and 3.
- The data items that operator act upon are called operands.

Expression
- An expression is a combination of variables, constants and operators written according to
syntax of the language.
E.g. 7+8, x+y*z, a>b

Types of operator
C operators can be classified into following types:
 Arithmetic Operators
 Relational Operators
 Logical Operators
 Assignment Operators
 Increment and Decrement Operators
 Conditional Operators
 Bitwise Operators
 Special Operators

Arithmetic Operators
Arithmetic operators are used to perform arithmetic operations. There are five arithmetic
operators:

Division Rule:
- int/int = int
- float/float = float
- int/float = float
- float/int = float

Note: For modulo operator, the sign of the result is always the sign of the first operand.
E.g. 10%3=1, -10%3=-1, -10%-3=-1, 10%-3=1

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2 C Programming Reference Note

/* Program to Perform Arithmetic Operations in C */

#include<stdio.h>
int main()
{
int a = 12, b = 3;
int add, sub, mul, div, mod;
add = a + b;
sub = a - b;
mul = a * b;
div = a / b;
mod = a % b;
printf("Addition of two numbers a, b is : %d\n", add);
printf("Subtraction of two numbers a, b is : %d\n", sub);
printf("Multiplication of two numbers a, b is : %d\n", mul);
printf("Division of two numbers a, b is : %d\n", div);
printf("Modulus of two numbers a, b is : %d\n", mod);
}

Relational Operators
- Relational operators are used to compare two operands and taking decisions based on
their relation.
- Result of relational expression is either True(1) or False(0).
- Relational operators are used in decision making and loops.
- Relational operators are:

/* Program to compare two numbers whether they are equal or not in C */

#include <stdio.h>
int main()
{
int m=40, n=20;
if (m == n)
{
printf("m and n are equal");
}
else
{
printf("m and n are not equal");
}
}

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3 C Programming Reference Note

Logical Operators
- Logical operators are used to compare logical and relational expression.
- The operands of logical operators must be either Boolean value (1 or 0) or expression that
produces Boolean value.
- The output of these operators is always 0 (flase) or 1 (true).
- The logical operators are:

Truth table for logical operators:

/* C program to demonstrate working of logical operators */

#include <stdio.h>
int main()
{
int a = 10, b = 4, c = 10, d = 20;

// logical AND example

if (a > b && c == d)
printf("a is greater than b AND c is equal to d\n");
else
printf("AND condition not satisfied\n");

// logical OR example
if (a > b || c == d)
printf("a is greater than b OR c is equal to d\n");
else
printf("Neither a is greater than b nor c is equal to d\n");

// logical NOT example

if (!a)
printf("a is zero\n");
else
printf("a is not zero");

return 0;
}

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4 C Programming Reference Note

Assignment Operator
- Assignment operators are used to assign the result of an expression to a variable.
- The mostly used assignment operator is ‘=’.
- C also supports shorthand assignment operators which simplify operation with
assignment.

/* program to demonstrate working of Assignment operators */

#include <stdio.h>
int main()
{
int a = 10;
printf("Value of a is %d\n", a); //10
a += 10;
printf("Value of a is %d\n", a); //20
a -= 10;
printf("Value of a is %d\n", a); //10
a *= 10;
printf("Value of a is %d\n", a); //100
a /= 10;
printf("Value of a is %d\n", a); //10
return 0;
}

Increment and Decrement Operators

- Increment operator is used to increase the value of an operand by 1.
- Decrement operator is used to decrease the value of an operand by 1.

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5 C Programming Reference Note

Pre-increment operator (++a): the value is incremented first and then the expression is
evaluated.
E.g. a= 10; b=++a; after this statement, a= 11, b = 11.
Post-increment operator (a++): the expression is evaluated first and then the value is
incremented.
E.g. a= 10; b=a++; after this statement, a= 11, b = 10.
Pre-decrement operator (- -a): the value is decremented first and then the expression is
evaluated.
E.g. a= 10; b=--a; after this statement, a= 9, b = 9.
Post-decrement operator (a- -): the expression is evaluated first and then the value is
decremented.
E.g. a= 10; b=a--; after this statement, a= 9, b = 10.

/* program to demonstrate working of increment and decrement operators */

#include <stdio.h>
int main()
{
int a = 5;
int b = 6;
printf("a=%d, b=%d",a,b); //a=5, b=6
b=++a;
printf("a=%d, b=%d",a,b); //a=6,b=6
b=a++;
printf("a=%d, b=%d",a,b); //a=7,b=6
b=a--;
printf("a=%d, b=%d",a,b); //a=6,b=7
b=--a;
printf("a=%d, b=%d",a,b); //a=5, b=5
return 0;
}

Conditional Operator (Ternary Operator)

- It takes three arguments.
- Conditional operators return one value if condition is true and returns another value if
condition is false.
Syntax: (condition) ? value_if_true : value_if_false

if a>b
return 1;
else
E.g. (a>b) ? 1 : 0; return 0;
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6 C Programming Reference Note

Q. Write a program to read two numbers from user and determine the larger number using
conditional (ternary) operator.
#include <stdio.h>
int main()
{
int n1, n2, larger;
printf("Enter two numbers:");
scanf("%d%d",&n1,&n2);
larger = (n1>n2)?n1:n2;
printf("The larger number is %d", larger);
return 0;
}

Bitwise Operator
- Bitwise operators are used for manipulating data at bit level.
- These operators are used for testing the bits or shifting them to the left or to the right.
- Can be applied only to integer-type operands and not to float or double.
- Three types of bitwise operators:
(i) Bitwise logical operators
(ii) Bitwise shift operators
(iii) One’s compliment operator

Bitwise logical operators:

- Performs logical tests between two integer-type operands.
- These operators work on their operands bit-by-bit starting from the least significant (i.e.
rightmost) bit.
- Three logical bitwise operators:
 Bitwise AND (&): The result of ANDing operation is 1 if both the bits have a value 1;
otherwise it is 0.
 Bitwise OR (|): The result of ORing operation is 1 if either of the bits have value of 1;
otherwise it is 0.
 Bitwise XOR (^): The result of exclusive ORing operations is 1 only if one of the bits
have a value of 1; otherwise it is 0.

Truth table for bitwise operators (AND, OR, XOR)

E.g.
If a = 65, b=15
Equivalent binary values of 65 = 0100 0001; 15 = 0000 1111

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7 C Programming Reference Note

Bitwise shift operators:

- Are used to move bit patterns either to left or to the right.
- There are two bitwise shift operators:
 Left shift(<<): Causes the operand to be shifted to the left by n positions.
operand<<n
The leftmost n bits in the original bit pattern will be lost and the rightmost n bits empty
position will be filled with 0’s.
 Right shift(>>): Causes the operand to be shifted to the right by n positions.
operand<<n
The empty leftmost n bits positions will be filled with 0’s, if the operand is an unsigned
integer.
E.g.
If a =15; Equivalent binary value of a is 0000 1111

0 0 1 1

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8 C Programming Reference Note

Bitwise one’s complement operator:

- It is a unary operator which inverts all the bits represented by its operand. This means that
all 0s becomes 1s and 1s becomes 0s.
E.g.
If a =15; Equivalent binary value of a is 0000 1111

/* program to demonstrate working of bitwise operator */

#include <stdio.h> #include <stdio.h>

void main() void main()
{ {
int a=65,b=15,AND, OR, XOR; unsigned int a=15, left, right;
AND = a&b; left = a<<3;
OR = a|b; right = a>>2;
XOR = a^b; printf("%d\n", left);
printf("AND of a and b=%d\n",AND); printf("%d\n",right);
printf("OR of a and b=%d\n",OR); }
printf("XOR of a and b=%d\n",XOR);
}

Special Operators
 Comma operator (,):
- The comma operator can be used link related expressions together.
- A comma-linked list of expression are evaluated from left-to-right and the value of the
rightmost expression is the value of the combined expressions.
E.g. X=(a=5, b=10, a+b);
- The first assign the value 5 to a
- Assign the value 10 to b
- Assign sum(a+b) to X

 Sizeof operator
- It is used with an operand to return the number of bytes it occupies.
- The operand may be constant, variable or a data type qualifier.

E.g.

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9 C Programming Reference Note

#include <stdio.h>
int main()
{
int a;
float b;
double c;
char d;
printf("Size of int=%lu bytes\n",sizeof(a));
printf("Size of float=%lu bytes\n",sizeof(b));
printf("Size of double=%lu bytes\n",sizeof(c));
printf("Size of char=%lu byte\n",sizeof(d));
return 0;
}

Operator precedence and associativity

- The precedence is used to determine how an expression involving more than one operator
is evaluated.
- There are distinct level of precedence.
- The operator at the higher level of precedence are evaluated first.
- Operators of same precedence are evaluated either from “left to right” or “right to left”
depending on the level also known as associativity.

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10 C Programming Reference Note

Type conversion in expressions

- When variables and constants of different types are combined in an expression then they
are converted to same data type.
- The process of converting one predefined type into another is called type conversion.
- Type conversion in C can be classified into the following two types:

1. Implicit Type Conversion:

- When the type conversion is performed automatically by the compiler without

programmer‘s intervention, such type of conversion is known as implicit type
conversion or type promotion.
- When the expression contains different types of data items, the operand with a lower
rank will be converted to the type of higher rank operand.

E.g.
#include <stdio.h>
int main()
{
int x = 13; // integer x
char c = 'a'; // character c
float sum;
x = x + c; // c implicitly converted to int. ASCII ('a'=97)
sum = x + 1.0; // x is implicitly converted to float
printf("x = %d, sum = %f", x, sum);
return 0;
}

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11 C Programming Reference Note

2. Explicit Type Conversion:

- The type conversion performed by the programmer by posing the data type of the
expression of specific type is known as explicit type conversion.
- The explicit type conversion is also known as type casting.
- Type casting in C is done in the following form:
(data_type)expression;
where, data_type is any valid C data type, and expression may be constant, variable
or expression.

E.g.
#include<stdio.h>
int main()
{
float a = 1.2;
int b;
b = (int)a + 1; // a is explicitly converted to int type
printf("Value of a is %f\n", a);
printf("Value of b is %d\n",b);
return 0;
}

Some Q &A

Q. Find the value of ‘a’ in each of the following statements:

int i=2, j=5, k=7
float a=1.5, b=2.5, c=3.5

i) a = c - i/j + c/k
= 3.5 - 2/5 + 3.5/7
= 3.5 – 0 + 0.5 int/int = int, so 2/5= 0.4 = 0 (int part)
=4

ii) a = (b+4)%(c+2)
= (2.5+4)%(3.5+2)
= 6.5%5.5
= Not valid

iii) a = c + k%2 + b
= 3.5 + 7%2 + 2.5
= 3.5 + 1+ 2.5
=7

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12 C Programming Reference Note

Q. Use the value initially assigned to the variable for each expression. Find the value of
following operations.
int a=8, b=5;
float x=0.005, y=-0.01;

i) (x>y)&&(a>0)||(b<5);
= (0.005>-0.01)&&(8>0)||(5<5)
= (1)&&(1)||(0)
= 1 || 0
=1

ii) (a>b)?a:b;
= (8>5)?8:5;
=8

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