1. Operators and Expressions
Knowledge:
Know the types of basic arithmetic operators and their order of precedence
Skill:
Develop skills in computer arithmetic
FTSM
Computer Science Department

2. Introduction
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
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3. W + Z Operator and Operand Operand Operand Operator
What are operator and operand?
Example:
W + Z
Operand
Operand
Operator
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4. A / B Operator and Operand Operator ?? Operand?? Which is which?
Example:
A / B
Operand??
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5. Basic Arithmetic Operators
Addition (+)
Modulus (%)
Subtraction (-)
Multiplication (*)
Division (/)
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6. Basic Arithmetic Operators
Multiplication, addition and subtraction are the simplest to use
Division is easy, but some precautions need to be taken
Modulus is the one that normally confuses novices
So, let’s study in detail the Division and Modulus
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7. W / Z Division Integer Division W and Z are integers Floating Division
Example:
W / Z
Integer Division
W and Z are integers
Floating Division
W or Z or both are floats
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8. 8 / 2 = 4 Integer Division  the result is also an integer an integer
Example:
8 / 2 = 4
an integer
 the result is also an integer
an integer
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9. 12 / 5 = 2 Integer Division  the result is also an integer an integer
Example:
12 / 5 = 2
an integer
 the result is also an integer
an integer
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10. 12.0 / 5 = 2 Floating Division a float an integer
Example:
12.0 / 5 = 2
a float
the result is a float
an integer
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11. Something to ponder …
What will be the answer if an integer is divided by 0? How about if one of the operands is a negative integer?
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12. Modulus
It returns the remainder that occurs after performing the division of 2 operands
Rule: Operands must be integers
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13. 12 % 5 = 2 Modulus an integer an integer
Example:
12 % 5 = 2
an integer
the result is the remainder of 12/5
an integer 2
result 5 12 10
remainder 2
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14. 7 % 3 = 1 Modulus an integer an integer
Example:
7 % 3 = 1
an integer
the result is the remainder of 7/3
an integer 2
result 3 7 6
remainder 1
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15. 12.0 % 3 = ?? Modulus a float an integer INVALID! Example:
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16. Something to ponder …
The earlier expressions contain only one operator at a time. What if the expression contains more than one operator?
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17. Arithmetic Expression
An expression may contain 2 or more arithmetic operators
Main issue:
ORDER OF PRECEDENCE
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18. Arithmetic Expression
Examples:
5 + 6
= 11
5 + 6 * 2
= 17
= 22 or 17?
– 2 * 2
= ??
= ??
12 / 6.0 – 2 * 2
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19. Arithmetic Expression
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
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20. Arithmetic Expression
Example:
Example:
– 2 * 2 = 4.5 4
8.5 –
– 4
4.5
– 2 * 2 =
– 2 * 2 = ??
– 2 * 2 = – 4
8.5
– 4
4.5
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21. Try it! 12 + 6.0 – 2 * 2 = ?? What’s the answer?? Example:
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22. Arithmetic 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:
( 9 – ( ) ) * 3 = ??
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23. Arithmetic Expression
Example:
( 9 – ( ) ) * 3 = ??
 ( 9 – ( ) ) * 3 = 12 – 12 4
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24. Assignment Statement There are 3 types of assignment: Simple Multiple
Shorthand
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25. variable = expression ;
Simple Assignment
Syntax:
variable = expression ;
Don’t forget the semicolon !!
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26. Simple Assignment 0.25 10.00 ?? 7.50 Example: price discount total
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 _
Buying price: 10.00
Discount rate: 0.25 _
0.25
Buying price: 10.00
Discount rate: _
Buying price: 10.00 _
10.00
Buying price: _
Simple Assignment
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); }
discount ??
price
total
7.50
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27. variable = variable = expression ;
Multiple Assignment
Syntax:
variable = variable = expression ;
Don’t forget the semicolon !!
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28. Multiple Assignment Example: int number, total;
float start_x, start_y;
. . .
number = total = 0;
start_x = start_y = 100.0;
total ??
number
start_x ??
start_y
100.0
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29. Shorthand Assignment variableX = variableX op expression ;
Syntax:
variableX = variableX op expression ;
variableX op= expression;
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30. Shorthand Assignment Example: 15 + 5 20 num = num + 5;
Whenever the expression on the right contains the variable on the left (to which the value is assigned)
Example:
num = num + 5;
num 15 20
15 + 5
20
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31. Shorthand Assignment Example: similar to num = num + 5 num += 5;
Expressions can also be stated using shorthand assignment operators
Example:
num += 5;
shorthand assignment operator
similar to num = num + 5
Shorthand assignment operators have the lowest order of precedence – the last one to be evaluated
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32. Examples of expression
Shorthand Assignment
Operation
Examples of expression
Description +=
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;
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33. Shorthand Assignment Example: pay += hour * rate * 2
similar to pay = pay + (hour * rate * 2)
180.00
pay
100.00
hour 8
rate
5.00
pay + (hour * rate * 2)
 pay + (8 * 5.00 * 2)  
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34. Assignment by Value Every assignment expression has a value
Example:
int a, x, y, p;
Line 1: a=1;
Line 2: x = y = 0;
Line 3: p = 12;
Line 4: p = p +3;
Line 5: q = p = p + x;
Example:
Expression 1: a = 1;
Expression 2: x = y = 0;
Expression 3: p = 12;
p = 0;
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35. Examples of Expression
Relational Operators
Operation
Description
Examples of Expression
Value
<
Less than
6 < 9
1 (true)
<=
Less than or equal to
5 <= 5
>
Greater than
2 > 6
0 (false)
>=
Greater than or equal to
9 >= 5 ==
Equal to
7 == 5 !=
Not equal to
6 != 5
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36. Mantic/Logical Operators
Symbol Description
&& AND
|| OR
! NOT a b
a && b
a || b !a !b 1
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37. Compound Statement ! ( c > a ) Example:
Arithmetic, relational and mantic operators can be integrated/combined in one expression
Example:
! ( c > a ) a 2 b 5
! ( 15 > 2 ) c 15
 ! ( 1 ) d 17
 0
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38. Compound Statement (a >= 1) && (b == 5) Example:2
1 && ( b == 5 ) b 5
1 && ( 5 == 5 ) c 15
1 && 1 d 17 1
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39. Compound Statement (c >= ( b * 3 ) ) || (a == 3) Example:
( c >= ( 5 * 3 ) ) || ( a == 3) a 2
( 15 >= 15 ) || ( a == 3) b 5
1 || ( a == 3 )
1 || ( 2 == 3 ) c 15
1 || 0 d 17 1
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40. Compound Statement ! ( ( a < b ) || ( c > d ) ) Example:2
! ( 1 || ( c > d ) ) b 5
! ( 1 || ( 15 > 17 ) )
! ( 1 || 0 ) c 15
! 1 d 17
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41. Increment and Decrement
This operation contains only one operand, that is, the operand which value will be incremented/
decremented
Symbol
Description
Examples of Expression ++
Increment operand by 1
i++
i = i + 1 --
Decrement operand by 1
i--
i = i – 1
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42. Increment and Decrement
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 ?? 26 27
Key-in a number: 26
Value before being incremented: 26
Value after being incremented: 27 _
Key-in a number: 26
Value before being incremented: 26 _
Key-in a number: _
Key-in a number: 26 _
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43. Prefix and Postfix
Increment and Decrement operators can be either in prefix or postfix forms
Expression
Description
i++
Value of i is incremented after being used in the expression
++i
Value of i is incremented before being used in the expression
i--
Value of i is decremented after being used in the expression
--i
Value of i is decremented before being used in the expression
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44. Prefix and Postfix Example: j = i++ - 2 similar to j = i – 2;
i = i + 1; i 5 6 j ?? 3
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45. Prefix and Postfix Example: j = ++i - 2 similar to i = i + 1;5 6 j ?? 4
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46. Coersion int x = 10; Example:
Coersion is used to compute a value that is equivalent to its operand’s value (based on the stated data type)
Example:
int x = 10;
float y;
y = (float) x; x 10 y ??
( float ) 10
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47. Coersion int total, number; Example: float average; …
average = total / number;
total 15
number 2
average ??
15 / 2 7
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48. Coersion int total, number; Example: float average; …
average = (float) total / number;
total 15
number 2
average ??
/ 2
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49. End of Lecture 6 Yes !! That’s all? What’s next???
CONTROL STRUCTURE: SELECTION on the way …
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