This document provides an overview of arithmetic, logical expressions, and conditional statements in C++. It discusses arithmetic operators for calculations, logical expressions using relational operators, and Boolean logic. Conditional constructs like if, if-else, and if-else-if statements are explained, along with examples of using them to make decisions based on expression evaluations. Operator precedence is also covered. The document aims to help readers learn about expressions and selection structures in C++.

1. Chapter 4
Arithmetic and Logical
Expressions
BTE2313 Computer Programming
Lecturer: Samson Mekbib

2. LEARNING OUTCOME
Learn about arithmetic operators to preform
calculations in C++
Explain how to solve and create a logical
expression
Explain how to use operators AND ( && )
and OR ( l l )

3. LEARNING OUTCOME
Learn about arithmetic operators to preform
calculations in C++
Explain how to solve and create a logical
expression
Explain how to use operators AND ( && )
and OR ( l l )

4. Operator shortcuts

5. Example: Operator shortcuts

6. Logical relationship
To make decisions, you must be able to express conditions and
make comparisons
 Stating conditions and making comparisons
In C++ a condition is represented by a logical (Boolean)
expression
True and False are logical (Boolean) values
RELATIONAL OPERATORS: A relational operator allows you to
make comparison in a program
Relational operators:
 Allow comparison
 Require two operands
 Evaluate to True or False

7. Relational operators in C++
N.B. : In C++, the symbol ==, which consists of two equal signs, is
called the equivalence operator and determines whether two expressions
are equal, whereas the assignment operator =, assigns the value of an
expression to a variable.
Operator Description Example True when
Value of num is
False when
value of num is
== Equal to num == 10 10 Other than 10
!= Not equal to num != 10 Other than 10 10
> Bigger than num > 10 Bigger than 10 10 or smaller
>= Bigger than or equal num >= 10 10 or bigger Smaller than 10
< Less than num < 10 Smaller than 10 10 or bigger
<= Less than or equal num <= 10 10 or smaller Bigger than 10
! Not !(num==10) Other than 10 10

8. Relational operators and
simple data types
You can use the relational operators with all the simple data
types
Examples with integers and real numbers
Expression Meaning Value
8 < 15 8 is less than 15 true
6 != 6 6 is not equal to 6 false
2.5 > 5.8 2.5 is greater than 5.8 false
5.9 <= 7.5 5.9 is less than or equal to 7.5 true

9. Example: Equality of floating point
numbers

10. Boolean Algebra
Or truth table
P Q P or Q
False False False
False True True
True False True
True True True

11. Boolean Algebra
Not truth table
P not P
False True
True False

12. Boolean Algebra
Can create complex logical expressions by combining simple
logical expressions
Example
 not (P and Q)
A truth table can be used to determine when a logical
expression is true
P Q P and Q not (P and Q)
False False False True
False True False True
True False False True
True True True False

13. A Boolean Type
C++ contains a data type named bool
Type bool data type has two symbolic constants
 true
 false
Examples
 bool P = true;
 bool Q = false;
 bool R = true;
 bool S = (P && Q);
The insertion and extraction operators could be used with bool types
In the output bool objects are displayed in binary notations (0 or 1)
Example:
cout << P << endl;
will print out either 1 or 0, depending on whether P is true or false
respectively

14. A Boolean Type
Example: Suppose the following bool type objects are defined
bool P = true;
bool Q = false;
bool R = true;
bool S = false;
Then,
P is true Q
P && R P && S
P l l Q Q l l S
!S !R
true false

15. Logical (Boolean) Operators

16. Examples of logical
expressions

17. Operator Precedence Revisited
Level Operator Associativity Type
1 () Left to right Parentheses
2 +, -, ++, --, ! Right to left Unary
3 *, /, % Left to right Multiplicative
4 +, - Left to right Additive
5 <<, >> Left to right Insertion/extraction
6 <, <=, >, >= Left to right Relational
7 ==, != Left to right Equality
8 && Left to right Logical AND
9 l l Right to left Logical OR

18. Operator Precedence Revisited
Example: Consider
5 * 15 + 4 == 13 && 12 < 19 || !false == 5 < 24
Is equivalent to:
((((5 *15) + 4) == 13) && (12 < 19))
||
((!false) == (5 < 24))
N.B. This is just an example and you will not be
using such complicated statements in your
programs.

19. Introductions on next chapter
Conditional / Selection Structure

20. Examples: Simple conditional
statements
if (score is greater than or equal to 90)
grate is A
if (hours worked are less than or equal to 40)
wages = rate * hours
Otherwise
wages = (rate * 40) + 1.5 * (rate * (hours -40))
if (temperature is greater than 20 degrees and it is not raining)
go to play golf!

21. Conditional Constructs in C++
Provide
 Ability to control whether a statement list is executed
Two constructs
 If statement
 if
 if-else
 if-else-if

22. The Basic If Statement
Syntax
if (Expression)
Action
If the Expression is true then
execute Action
Action is either a single
statement or a group of
statements within braces
Expression
Action
true false

23. Example
if (Value < 0) {
Value = -Value;
}
Value < 0
Value = -Value
true f alse
Is our number negative?
If Value is not less
than zero then our
number is fine as is
If Value is less than
zero then we need to
update its value to
that of its additive
inverse
Our number is
now definitely
nonnegative

24. Sorting Two Numbers
cout << "Enter two integers: ";
int Value1;
int Value2;
cin >> Value1 >> Value2;
if (Value1 > Value2) {
int RememberValue1 = Value1;
Value1 = Value2;
Value2 = RememberValue1;
}
cout << "The input in sorted order: "
<< Value1 << " " << Value2 << endl;

25. Semantics
value2 < value1
int rememberValue1 = value1
value1 = value2
value2 = rememberValue1
true f alse
Are the numbers
out of order
Rearrange value1
and value2 to
put their values
in the proper
order
The numbers were
initially in order
The numbers were
rearranged into the
proper order
The numbers are in
order

26. What is the Output?
int m = 5;
int n = 10;
if (m < n)
++m;
++n;
cout << " m = " << m << " n = " n << endl;

27. The If-Else Statement
Syntax
if (Expression)
Action1
else
Action2
If Expression is true then execute
Action1 otherwise execute Action2
if (v == 0) {
cout << "v is 0";
}
else {
cout << "v is not 0";
}
Expression
Action1 Action2
true false

28. Finding the Max
cout << "Enter two integers: ";
int Value1;
int Value2;
cin >> Value1 >> Value2;
int Max;
if (Value1 < Value2) {
Max = Value2;
}
else {
Max = Value1;
}
cout << "Maximum of inputs is: " << Max << endl;

29. Finding the Max
Value1 < Value2
Max = Value2 Max = Value1
true f alse
Is Value2 larger than Value1
Yes, it is . So Value2 is
larger than Value1. In
this case, Max is set
to Value2
No, its not. So Value
is at least as large as
Value2. In this case
Max is set to Value1
Either case, Max is set
correctly

30. Selection
It is often the case that depending upon the value of an
expression we want to perform a particular action
Two major ways of accomplishing this choice
 if-else-if statement
 if-else statements “glued” together
 Switch statement
 An advanced construct

31. An If-Else-If Statement
if ( nbr < 0 )
{
cout << nbr << " is negative" << endl;
}
else if ( nbr > 0 )
{
cout << nbr << " is positive" << endl;
}
else
{
cout << nbr << " is zero" << endl;
}