Operatorsand

Expressions

Unit 4

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Operators• Symbol that operates on certain data type or data item.

• Used in program to perform certain mathematical or logical manipulations.

• Ex: in a simple expression 5+6, the symbol “+” is called an operator which operates on two data items 5 and 6.

• The data items that operator act upon are called operands.

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Expression

• An expression is a combination of variables, constants and operators written according to syntax of the language.

• Ex:8+10 a+c*d a>b a/c

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• We can classify operators into – Unary operators• Which requires only one operand• Ex. ++ , --, +,-

– Binary operators• Which requires two operands• Ex. +,-,*, / , < , > etc.

– Ternary operators• Which require three operands• Ex. “ ?: ” (conditional operator)

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• Ternary operators can be further classified into following categories:

–Arithmetic Operators–Relational Operators–Logical Operators–Assignment Operators– Increment and Decrement Operators–Conditional Operators–Bitwise Operators–Special Operators

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Arithmetic OperatorsAssume variable A holds 10 and variable B holds 20 then

Operator Description Example

+ Adds two operands. A + B = 30

− Subtracts second operand from the first. A − B = 10

* Multiplies both operands. A * B = 200

/ Divides numerator by de-numerator. B / A = 2

% Modulus Operator and remainder of after an integer division.

B % A = 0

++ Increment operator increases the integer value by one.

A++ = 11

-- Decrement operator decreases the integer value by one.

A-- = 9

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Integer Arithmetic• Division Rule– Int / int =int– Float / float= float– Int / float = float– Float /int =float

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#include <stdio.h>Void main() {

int a = 21; int b = 10; int c ; c = a + b; printf("Line 1 - Value of c is %d\n", c ); c = a - b; printf("Line 2 - Value of c is %d\n", c ); c = a * b; printf("Line 3 - Value of c is %d\n", c ); c = a / b; printf("Line 4 - Value of c is %d\n", c ); c = a % b; printf("Line 5 - Value of c is %d\n", c ); c = a++; printf("Line 6 - Value of c is %d\n", c ); c = a--; printf("Line 7 - Value of c is %d\n", c );

}

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Relational OperatorsAssume variable A holds 10 and variable B holds 20

Operator Description Example

== Checks if the values of two operands are equal or not. If yes, then the condition becomes true.

(A == B) is not true.

!= Checks if the values of two operands are equal or not. If the values are not equal, then the condition becomes true.

(A != B) is true.

> Checks if the value of left operand is greater than the value of right operand. If yes, then the condition becomes true.

(A > B) is not true.

< Checks if the value of left operand is less than the value of right operand. If yes, then the condition becomes true.

(A < B) is true.

>= Checks if the value of left operand is greater than or equal to the value of right operand. If yes, then the condition becomes true.

(A >= B) is not true.

<= Checks if the value of left operand is less than or equal to the value of right operand. If yes, then the condition becomes true.

(A <= B) is true.

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#include <stdio.h>main() {

int a = 21; int b = 10; int c ; if( a == b ) { printf("Line 1 - a is equal to b\n" ); } else { printf("Line 1 - a is not equal to b\n" ); }

if ( a < b ) { printf("Line 2 - a is less than b\n" ); } else { printf("Line 2 - a is not less than b\n" ); } if ( a > b ) { printf("Line 3 - a is greater than b\n" ); } else { printf("Line 3 - a is not greater than b\n" ); } /* Lets change value of a and b */ a = 5; b = 20; if ( a <= b ) { printf("Line 4 - a is either less than or equal to b\n" ); } if ( b >= a ) { printf("Line 5 - b is either greater than or equal to b\n" ); }

}

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Logical Operators

Assume variable A holds 1 and variable B holds 0Operator Description Example

&& Called Logical AND operator. If both the operands are non-zero, then the condition becomes true.

(A && B) is false.

|| Called Logical OR Operator. If any of the two operands is non-zero, then the condition becomes true.

(A || B) is true.

! Called Logical NOT Operator. It is used to reverse the logical state of its operand. If a condition is true, then Logical NOT operator will make it false.

!(A && B) is true.

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Void main() { int a = 5; int b = 20; int c ; if ( a && b ) {

printf("Line 1 - Condition is true\n" ); } if ( a || b ) {

printf("Line 2 - Condition is true\n" ); } /* lets change the value of a and b */ a = 0; b = 10; if ( a && b ) {

printf("Line 3 - Condition is true\n" ); } else {

printf("Line 3 - Condition is not true\n" ); }

if ( !(a && b) ) { printf("Line 4 - Condition is true\n" );

} }

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Assignment OperatorsOperator Description Example

= Simple assignment operator. Assigns values from right side operands to left side operand

C = A + B will assign the value of A + B to C

+= Add AND assignment operator. It adds the right operand to the left operand and assign the result to the left operand.

C += A is equivalent to C = C + A

-= Subtract AND assignment operator. It subtracts the right operand from the left operand and assigns the result to the left operand.

C -= A is equivalent to C = C - A

*= Multiply AND assignment operator. It multiplies the right operand with the left operand and assigns the result to the left operand.

C *= A is equivalent to C = C * A

/= Divide AND assignment operator. It divides the left operand with the right operand and assigns the result to the left operand.

C /= A is equivalent to C = C / A

%= Modulus AND assignment operator. It takes modulus using two operands and assigns the result to the left operand.

C %= A is equivalent to C = C % A

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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 1Operator Description Example

++ ++variable (prefix notation) Variable = variable + 1

++ variable++ (postfix notation) Variable= variable + 1

-- - -variable (prefix notation) Variable =variable - 1

-- variable- - (postfix notation) Variable =variable - 1

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void main(){int a= 10;clrscr();printf("a =%d",a);printf("a =%d",++a);printf("a =%d",a++);printf("a =%d",a);

}

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void main(){int a= 10;clrscr();printf("a =%d",a);printf("a =%d",++a);printf("a =%d",a++);printf("a =%d",a);

}

OUTPUT:a=10a=11a=11a=12

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Conditional Operator

• The operator pair “?:” is known as conditional operator.• It takes three operands. Also called ternary operator.• General form:

expression1 ? expression 2 : expression 3• expression1 is evaluated first

If expression1 is true then value of expression2 is the value of condition

expressionelse

the value of expression3 is the value of conditional expression

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void main(){

int n1,n2, larger;clrscr();printf("Enter Two numbers:");scanf("%d%d",&n1,&n2);

larger= n1>n2 ? n1 : n2;printf("The larger number is %d", larger);getch();

}

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Bitwise Logical 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

– Bitwise logical operators

– Bitwise shift operators

– One’s complement operator

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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(&)

– Bitwise OR( | )

– Bitwise Exclusive OR (^)

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Bitwise And (&)

• Logical ANDing between two operands.

• The result of ANDing operation is 1 if both the bits have a

value of 1; otherwise it is 0.

• Consider n1=60 and n2=15

– N1 0000 0000 0011 1100

– N2 0000 0000 0000 1111

• If n3= n1 & n2;

– n3 0000 0000 0000 1100

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Bitwise OR( | )• ORing between two operands

• The result of Oring operations is 1 if either of the bits have

value of 1; otherwise it is 0.

• Consider n1=60 and n2=15

– N1 0000 0000 0011 1100

– N2 0000 0000 0000 1111

• If n3= n1 | n2;

– n3 0000 0000 0011 1111

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Bitwise Exclusive XOR ( ^ )• The result of Exclusive ORing operations is 1 only

if one of the bits have a value of 1; otherwise it is 0.

• Consider n1=60 and n2=15

– N1 0000 0000 0011 1100

– N2 0000 0000 0000 1111

• If n3= n1 & n2;

– n3 0000 0000 0011 0011

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#include<stdio.h>void main(){

int n1=60,n2=51,AND, OR, XOR;AND= n1 & n2;OR= n1 | n2;XOR= n1 ^ n2;printf("AND=%d\n",AND ); printf("OR=%d\

n",OR ); printf("XOR=%d\n",XOR );}

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Bitwise Shift Operators• Are used to move bit patterns either to the left

or to the right.

• There are two bitwise shift operators– Left shift ( << )– Right shift ( >> )

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• 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 positions will be filled with 0’s.

– Ex n1=60• Execute the statement n2= n1 <<3;

n1 0000 0000 0011 1100

Shift 1 0000 0000 0111 1000

Shift 2 0000 0000 1111 0000

Shift 3 0000 0001 1110 0000 (==n2)

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• 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.

– Ex unsigned int n1=60;• Execute the statement n2= n1 >>3;

n1 0000 0000 0011 1100

Shift 1 0000 0000 0001 1110

Shift 2 0000 0000 0000 1111

Shift 3 0000 0000 0000 0111 (==n2)

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Bitwise One’s Complement Operator

• Is a unary operator which inverts all the bits represented by its operand.

• This means that all 0s becomes 1s and 1s becomes 0s– If n1=60, then we execute the statement• n2= ~n1

– The resulting bit pattern represents the decimal: -61

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#include<stdio.h>voidmain(){

unsigned int n1=60 ,left, right;left =n1 << 3;right =n1 >> 3;

printf("%d \n", left);printf("%d\n", right);

}

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Special Operators• C supports some special operators and for

now we discuss– comma operator (,) – sizeof operator

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Comma operator• The comma operator can be used to link related expressions

together.

• A comma-linked list of expressions are evaluated from left-to-

right and the value of the rightmost expression is the value of

the combined expressions.

• Ex: n3=(n1=50, n2=10,n1+n2)

– The first assign the value 50 to n1

– Assign the value 10 to n2

– Assign sum n1+n2 to n3

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sizeof Operator• Is used with an operand to return the number

of bytes it occupies.

• The operand may be constant, variable or a data type qualifier.

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#include<stdio.h>Void main(){

unsigned int n1;printf("Integer Variable =>

%lu\n",sizeof(n1) );printf("Double Constant =>

%lu\n",sizeof(15.11) );printf("Long int Data type qualifier =>

%lu\n",sizeof(15L) );}

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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 operators 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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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

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• Ex” consider four integer type variable n1=9 n2=12 n3=3 and x

x = n1 –n2 / 3 + n3 *2 -1Becomes,

x= 9 -12 /3 + 3 * 2 -1

Step1: 9 -12 / 6 * (2-1)Step2: 9-12/6*1Step3: 9-2*1Step4: 9-2Step5: 7

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• Example x=20 and y=5

• If(x==10+15 && y<10)

– Step1: If(x==25 && y<10)

– Step2: if(20==25 && 5 < 10)

– Step3: if(20==25 && TRUE)

– Step3: if(FALSE && TRUE)

• Since one condition is FALSE, the whole condition is

FALSE.

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Solve this• Find the value of “a” in each of the following

statements: – int i = 3, j = 4, k =8; – float a = 4.5, b = 6.5, c = 3.5; • a=b-i/k+c/k • a = (b-k)/j + (j+c)/k • a = c - ((i+j)/(k+i)) *b • a=c-i+j/k+i*b • a=c+j%2+b • a=(b+1)%(c+1)

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END