computer science department ftsm operators and expressions knowledge: know the types of basic...

Computer Science Department FTSMFTSM

Operators and Operators and ExpressionsExpressions

Knowledge:Know the types of basic arithmetic operators and their order of precedence

Skill:Develop skills in computer arithmetic

TK1913-C ProgrammingTK1913-C Programming 22

We use arithmetic expressions to solve

most programming problems

Arithmetic expressions comprise of

operators and operands

There are rules for writing and

evaluating arithmetic expressions

IntroductionIntroduction


Operator and OperandOperator and Operand

Example:Example:

W + ZW + Z

OperandOperand

OperatorOperator

OperandOperand

What are operator and operand?


Example:Example:

Operator and OperandOperator and OperandWhich is which?

A / BA / B

Operator ??Operator ??

Operand??Operand??


Basic Arithmetic OperatorsBasic Arithmetic Operators

Addition (+)Addition (+)

Subtraction (-)Subtraction (-)

Multiplication (*)Multiplication (*)

Division (/)Division (/)

Modulus (%)Modulus (%)


Basic Arithmetic OperatorsBasic Arithmetic Operators MultiplicationMultiplication, additionaddition and subtractionsubtraction are

the simplest to use

DivisionDivision is easy, but some precautions need to

be taken

ModulusModulus is the one that normally confuses

novices

So, let’s study in detail the DivisionDivision and ModulusModulus


DivisionDivisionExample:Example:

W / ZW / Z

Floating Division

WW or ZZ or both are

floats

Integer Division

WW and ZZ are integers


Example:Example:

Integer DivisionInteger Division

8 / 2 = 48 / 2 = 4

an integeran integer


the result is the result is also an integeralso an integer


Example:Example:

Integer DivisionInteger Division

12 / 5 = 212 / 5 = 2



the result is the result is also an integeralso an integer


Example:Example:

Floating DivisionFloating Division

12.0 / 5 = 212.0 / 5 = 2

a floata float


the result is a the result is a floatfloat


What will be the answer What will be the answer if an integer is divided if an integer is divided by 0? How about if one by 0? How about if one of the operands is a of the operands is a negative integer?negative integer?

Something to ponder …Something to ponder …


ModulusModulus It returns the remainderremainder that occurs

after performing the division of 2 operands

Rule:Rule: Operands must be integersintegers


Example:Example:

ModulusModulus

12 % 5 = 212 % 5 = 2



the result is the the result is the remainder of remainder of 12/512/5

1252

10

2

remainderresult


Example:Example:

ModulusModulus

7 % 3 = 17 % 3 = 1



732

6

1

remainderresult

the result is the the result is the remainder of 7/3remainder of 7/3


Example:Example:

ModulusModulus

12.0 % 3 = ??12.0 % 3 = ??

a floata float


INVALID!INVALID!


The earlier expressions The earlier expressions contain only one contain only one operator at a time. What operator at a time. What if the expression if the expression contains more than one contains more than one operator? operator?

Something to ponder …Something to ponder …


An expression may contain 2 or more

arithmetic operators

Main issue:

ORDER OF PRECEDENCEORDER OF PRECEDENCE

Arithmetic ExpressionArithmetic Expression


Examples:Examples:

5 + 65 + 6

5 + 6 * 25 + 6 * 2

2.5 + 6 – 2 * 22.5 + 6 – 2 * 2

12 / 6.0 – 2 * 212 / 6.0 – 2 * 2

= 11= 11

= 22 or 17?= 22 or 17?

= ??= ??

= ??= ??

= 17= 17



Arithmetic ExpressionArithmetic ExpressionOrder of Precedence:Order of Precedence:

High: * / %* / %Low: + -+ -

All operators have a precedence level. High precedence level operators are evaluated before lower ones. Operators of the same precedence level are evaluated from left to right


Example:Example:


2.5 + 6 – 2 * 2 = ??2.5 + 6 – 2 * 2 = ??

44

8.58.5

2.5 + 6 –2.5 + 6 –

– – 44

4.54.5

2.5 + 6 – 2 * 2 = 2.5 + 6 – 2 * 2 = Example:Example:2.5 + 6 – 2 * 2 = 4.52.5 + 6 – 2 * 2 = 4.5

44

8.58.5

2.5 + 6 –2.5 + 6 –

– – 44

4.54.5

2.5 + 6 – 2 * 2 = 2.5 + 6 – 2 * 2 =


Example:Example:

Try it!Try it!

12 + 6.0 – 2 * 2 = ??12 + 6.0 – 2 * 2 = ??

What’s the answer??What’s the answer??


Arithmetic ExpressionArithmetic Expression All expressions in parentheses (brackets) must

be evaluated prior to values outside brackets Nested parenthesized expressions must be

evaluated from the inside out, with the innermost expression evaluated first

Example:Example:

( 9 – ( 3 + 2 ) ) * 3 = ??( 9 – ( 3 + 2 ) ) * 3 = ??



Example:

( 9 – ( 3 + 2 ) ) * 3 = ??( 9 – ( 3 + 2 ) ) * 3 = ??

Example:

( 9 – ( 3 + 2 ) ) * 3 = ??( 9 – ( 3 + 2 ) ) * 3 = ?? – – 5544 1212 ( 9 – ( 3 + 2 ) ) * 3 = 12( 9 – ( 3 + 2 ) ) * 3 = 12


Assignment StatementAssignment Statement

There are 3 types of assignment:

Simple

Multiple

Shorthand


Simple AssignmentSimple AssignmentSyntax:

variable = expression ;variable = expression ;

Don’t forget the semicolon !!Don’t forget the semicolon !!


Simple AssignmentSimple AssignmentExample:#include <stdio.h>void main( ) { float price, discount, total; printf(“Buying price : “); scanf(“%f”, &price); printf(“\nDiscount rate : “); scanf(“%f”, &discount); total = price – (price * discount); printf(“\nFor buying price RM%.2f and discount rate %.2f\n”, price, discount); printf(“The total price is RM%.2f\n”, total);

}

Example:#include <stdio.h>void main( ) { float price, discount, total; printf(“Buying price : “); scanf(“%f”, &price); printf(“\nDiscount rate : “); scanf(“%f”, &discount); total = price – (price * discount); printf(“\nFor buying price RM%.2f and discount rate %.2f\n”, price, discount); printf(“The total price is RM%.2f\n”, total);

}

Buying price: _

discount ??

price ??

total ??

Buying price: 10.00

_

10.00

Buying price: 10.00

Discount rate: _

Buying price: 10.00

Discount rate: 0.25

_

0.25

7.50

Buying price: 10.00

Discount rate: 0.25

For buying price RM10.00 and discount rate 0.25

_

Buying price: 10.00

Discount rate: 0.25

For buying price RM10.00 and discount rate 0.25

The total price is RM7.50

_


Syntax:

variable = variable = expression ;variable = variable = expression ;

Multiple AssignmentMultiple Assignment

Don’t forget the semicolon !!Don’t forget the semicolon !!


Example:

int number, total;

float start_x, start_y;

. . .

number = total = 0;

start_x = start_y = 100.0;

Example:

int number, total;

float start_x, start_y;

. . .

number = total = 0;

start_x = start_y = 100.0;

total ??

number ??

start_x ??

start_y ??

0

0

100.0

100.0

Multiple AssignmentMultiple Assignment


Shorthand AssignmentShorthand Assignment

Syntax:

variableX = variableX variableX = variableX opop expression ; expression ;

variableX variableX opop= expression;= expression;


Whenever the expression on the right contains the variable on the left (to which the value is assigned)

Example:

num = num + 5;

Example:

num = num + 5;

num 15

15 + 515 + 5

2020

20



Expressions can also be stated using shorthand assignment operators

Example:

num += 5;

Example:

num += 5; similar to similar to num = num + 5num = num + 5

shorthand assignment operatorshorthand assignment operator


Shorthand assignment operators have the lowest order of precedence – the last one to be evaluated


OperationOperation Examples of Examples of expressionexpression

DescriptionDescription

+= num += 5; num = num + 5;

-= num -= 5; num = num – 5;

*= num *= 5; num = num * 5;

/= num /= 5; num = num / 5;

%= num %= 5; num = num % 5;



Example:

pay += hour * rate * 2

Example:

pay += hour * rate * 2

pay + (8 * 5.00 * 2)pay + (8 * 5.00 * 2)

pay 100.00

hour 8

rate 5.00

similar to similar to pay = pay + (hour * rate * 2)pay = pay + (hour * rate * 2)

pay + (hour * rate * 2)pay + (hour * rate * 2)

100.00 + 80.00100.00 + 80.00 180.00180.00

180.00



Assignment by ValueAssignment by ValueEvery assignment expression has a value

Example:

Expression 1:Expression 1: a = 1;a = 1;

Expression 2:Expression 2: x = y = 0;x = y = 0;

Expression 3:Expression 3: p = 12;p = 12;

p = 0;p = 0;

Example:

Expression 1:Expression 1: a = 1;a = 1;

Expression 2:Expression 2: x = y = 0;x = y = 0;

Expression 3:Expression 3: p = 12;p = 12;

p = 0;p = 0;

Example: int a, x, y, p;int a, x, y, p;Line 1:Line 1: a=1;a=1;Line 2:Line 2: x = y = 0;x = y = 0;Line 3:Line 3: p = 12;p = 12;Line 4:Line 4: p = p +3;p = p +3;Line 5:Line 5: q = p = p + x;q = p = p + x;

Example: int a, x, y, p;int a, x, y, p;Line 1:Line 1: a=1;a=1;Line 2:Line 2: x = y = 0;x = y = 0;Line 3:Line 3: p = 12;p = 12;Line 4:Line 4: p = p +3;p = p +3;Line 5:Line 5: q = p = p + x;q = p = p + x;


Relational OperatorsRelational OperatorsOperationOperation DescriptionDescription Examples Examples

of of ExpressionExpression

ValueValue

< Less than 6 < 9 1 (true)

<= Less than or equal to 5 <= 5 1 (true)

> Greater than 2 > 6 0 (false)

>= Greater than or equal to 9 >= 5 1 (true)

== Equal to 7 == 5 0 (false)

!= Not equal to 6 != 5 1 (true)


Mantic/Logical OperatorsMantic/Logical OperatorsSymbol Description

&&&& ANDAND

|||| OROR

!! NOTNOT

aa bb a && ba && b a || ba || b !a!a !b!b0 0 0 0 1 1

0 1 0 1 1 0

1 0 0 1 0 1

1 1 1 1 0 0


Compound StatementCompound StatementArithmetic, relational and mantic operators can be

integrated/combined in one expression

Example:

! ( c > a )

Example:

! ( c > a )a 2

b 5

c 15

d 17 ! ( 1 )! ( 1 )

! ( 15 > 2 )! ( 15 > 2 )

00


Example:

(a >= 1) && (b == 5)

Example:

(a >= 1) && (b == 5)

a 2

b 5

c 15

d 17

( 2 >= 1 ) && ( b == 5 )( 2 >= 1 ) && ( b == 5 )

Compound StatementCompound Statement

1 && ( b == 5 )1 && ( b == 5 ) 1 && ( 5 == 5 )1 && ( 5 == 5 ) 1 && 11 && 1 11


Example:

(c >= ( b * 3 ) ) || (a == 3)

Example:

(c >= ( b * 3 ) ) || (a == 3)

a 2

b 5

c 15

d 17

( c >= ( 5 * 3 ) ) || ( a == 3)( c >= ( 5 * 3 ) ) || ( a == 3)


1 || ( a == 3 )1 || ( a == 3 ) 1 || ( 2 == 3 )1 || ( 2 == 3 ) 1 || 01 || 0

( 15 >= 15 ) || ( a == 3)( 15 >= 15 ) || ( a == 3)

11


Example:

! ( ( a < b ) || ( c > d ) )

Example:

! ( ( a < b ) || ( c > d ) )

a 2

b 5

c 15

d 17

! ( ( 2 < 5 ) || ( c > d ) )! ( ( 2 < 5 ) || ( c > d ) )


! ( 1 || ( 15 > 17 ) )! ( 1 || ( 15 > 17 ) ) ! ( 1 || 0 )! ( 1 || 0 ) ! 1 ! 1

! ( 1 || ( c > d ) )! ( 1 || ( c > d ) )

00


Increment and DecrementIncrement and DecrementThis operation contains only one operand, that is, the operand which value will be incremented/decremented

SymbolSymbol DescriptionDescription Examples of Examples of ExpressionExpression

DescriptionDescription

++ Increment operand by 1

i++ i = i + 1

-- Decrement operand by 1

i-- i = i – 1


Key-in a number: _Key-in a number: 26

_

Increment and DecrementIncrement and DecrementExample:int num;printf(“Key-in a number: “);scanf(“%d”, &num);printf(“Value before being incremented: %d\n”, num);num++;printf(“Value after being incremented: %d”, num);

Example:int num;printf(“Key-in a number: “);scanf(“%d”, &num);printf(“Value before being incremented: %d\n”, num);num++;printf(“Value after being incremented: %d”, num);

num ??

Key-in a number: 26

Value before being incremented: 26

_

2627

Key-in a number: 26

Value before being incremented: 26

Value after being incremented: 27 _


Prefix and PostfixPrefix and PostfixIncrement and Decrement operators can be either in prefix or postfix forms

ExpressionExpression DescriptionDescription

i++ Value of ii is incrementedincremented afterafter being used in the expression

++i Value of ii is incrementedincremented beforebefore being used in the expression

i-- Value of ii is decrementeddecremented afterafter being used in the expression

--i Value of ii is decrementeddecremented beforebefore being used in the expression


Example:

j = i++ - 2

Example:

j = i++ - 2

i 5

similar to similar to

j = i – 2;j = i – 2;

i = i + 1;i = i + 1;

Prefix and PostfixPrefix and Postfix

j ??3

6


Example:

j = ++i - 2

Example:

j = ++i - 2

i 5

similar to similar to

i = i + 1;i = i + 1;

j = i – 2;j = i – 2;

Prefix and PostfixPrefix and Postfix

j ??4

6


Example: int x = 10;

float y;y = (float) x;

Example: int x = 10;

float y;y = (float) x;

CoersionCoersion

( float ) 10( float ) 10 10.00000010.000000

x 10

y ??10.000000

Coersion is used to compute a value that is equivalent to its operand’s value (based on the stated data type)


Example: int total, number;

float average;…average = total / number;


float average;…average = total / number;

CoersionCoersion

15 / 215 / 2 77

total 15

number 2

average ??7.000000



float average;…average = (float) total / number;


float average;…average = (float) total / number;

CoersionCoersion

15.000000 / 215.000000 / 2 7.5000007.500000

total 15

number 2

average ??7.500000


End of Lecture 6End of Lecture 6

Yes !! That’s all? Yes !! That’s all? What’s next???What’s next???

CONTROL STRUCTURE: CONTROL STRUCTURE: SELECTIONSELECTION on the way … on the way …

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