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Frequently used data types

•float

and

double

data types for storing real numbers.

• The

float

data type has a precision of seven digits

-This means after the decimal point you can have seven digits

Example:

-3.14159 534.322344

0.1234567

•

The

double

data type has a precision of fifteen digits

-This means after the decimal point you can have fifteen digits

Example :

3738.7878787878 3.141592653589790

0.123456789123456

LECTURE # 5 :
STRUCTURED PROGRAMMING

C++ Operators

D. Abdalrahman R. Qubaa

First Class, System and Control Engineering Dep.

Content

Arithmetic Operations



Arithmetic Operators



Increment and decrement operators



Decision making operators (Equality, relational and

logical)



Conditional operator



Precedence and associativity of operators



Common errors

Arithmetic Operations



Operators: Data connectors within expression or equation



Operators types based on their mission

1. Arithmetic

: addition + , subtraction -, modulo division / , ...etc (x+y)

2. Equality and Relational

: equal to == , less than <, grater than >,

…etc

(x<y)

3. Logical :

NOT, AND, OR (x and y)

Operators



Operators types based on number of operands



Unary operators

◼

Have only one operand

◼

May be prefix or postfix

◼

e.g.

++ !

(

++ ,

--)



Binary operators

◼

Have two operands

◼

Infix

◼

e.g.

(

)



Ternary operators

◼

Have three operands

◼

e.g. ? : (

i > j

max=i

max=j

)

Assignment statement



Assignment statement takes the form below



Expression is evaluated and its value is assigned to the variable on

the left side



Shorthand notation



varName = varName

operator

expression;



varName

operator

= expression;

varName = expression;

c = c + 3;

c += 3;

Arithmetic Operators



Arithmetic Operators: All of them are binary operators



Arithmetic expressions appear in straight-line form



Parentheses () are used to maintain priority of manipulation

C++ operation

C++ arithmetic
operator

Algebraic
expression

C++ expression

Addition

f + 7

Subtraction

p - c

MUltiplication

bm or b . m

b * m

Division

x / y or x ÷ y

x / y

Modulus

r mod s

r % s

Assignment between objects



Assignment between objects of

the same type

is always supported

Assignment

operator

Sample

expression

Explnation

Assigns

Assume: int c = 3, d = 5, e = 4, f = 6, g = 12;

c += 7

c = c + 7

10 to c

d -= 4

d = d – 4

1 to d

e *= 5

e = e * 5

20 to e

f /= 3

f = f / 3

2 to f

g %= 9

g = g % 9

3 to g

Decision Making:

Equality

and

Relational Operators

Standard algebraic
equality operator or
relational operator

C++ equality
or relational
operator

Example
of C++
condition

Meaning of
C++ condition

Relational operators

x > y

is greater than y

x < y

is less than y



x >= y

is greater than or equal to y



x <= y

is less than or equal to y

Equality operators

x == y

is equal to y



x != y

is not equal to y

Arithmetic Operators Precedence



Operators in parentheses evaluated first



Nested/embedded parentheses (Operators in innermost pair first)



Multiplication, division, modulus applied next



Addition, subtraction applied last

(Operators applied from left to

right)

Operator(s)

Operation(s)

Order of evaluation (precedence)

()

Parentheses

Evaluated first. If the parentheses are nested, the
expression in the innermost pair is evaluated first. If
there are several pairs of parentheses “on the same level”
(i.e., not nested), they are evaluated left to right.

*, /, or %

Multiplication Division
Modulus

Evaluated second. If there are several, they re
evaluated left to right.

+ or -

Addition
Subtraction

Evaluated last. If there are several, they are
evaluated left to right.

Example



The statement is written in algebra as

z = pr % q + w / (x – y)

How can we write and evaluate the previous statement in C++ ?

z = p * r % q + w / (x -

y);

Example:

Exercise 1



State the order of evaluation of the operators in each of the
following C++ statements and show the value of

after

each statement is performed.



x = 7 + 3 * 6 / 2 - 1;



x = 2 % 2 + 2 * 2 - 2 / 2;



x = ( 3 * 9 * ( 3 + ( 9 * 3 / ( 3 ) ) ) );



324

Increment and Decrement Operators



Unary operators



Adding 1 to or (subtracting 1 from) variable

’s value



Increment operator gives the same result of

(c=c+1) or (c+=1)



Decrement operator gives the same result of

(c=c-1) or (c-=1)

Operator Called

Sample
expression

Explanation

Preincrement

++a

Increment a by 1, then use the new value of
a in the expression in which a resides.

Postincrement

a++

Use the current value of a in the expression
in which a resides, then increment a by 1.

−−

Pridecrement

--b

Decrement b by 1, then use the new value of
b in the expression in which b resides.

−−

Postdecrement

b--

Use the current value of b in the expression
in which b resides, decrement b by 1.

Examples

int

x = 10;

cout << “x = “ << ++x << endl;
cout << “x = “ << x << endl;

Example # 1

x = 11

output # 1

int

x = 10;

cout << “x = “ << x++ << endl;
cout << “x = “ << x << endl;

Example # 2

x = 10
x = 11

output # 2

Examples

int

x = 10 , y;

y = ++x;

cout << “x = “ << x << endl;
cout << “y = “ << y << endl;

Example # 1

x = 11
y = 11

output # 1

int

x = 10 , y;

y = x++;

cout << “x = “ << x << endl;
cout << “y = “ << y << endl;

Example # 2

x = 11
y = 10

output # 2

Relational and Equality Operators



Binary operators



Used in decision -making statements

Standard algebraic
equality operator or
relational operator

C++ equality
or relational
operator

Example
of C++
condition

Meaning of
C++ condition

Relational operators

x > y

is greater than y

x < y

is less than y



x >= y

is greater than or equal to y



x <= y

is less than or equal to y

Equality operators

x == y

is equal to y



x != y

is not equal to y

Relational and Equality Operators (cont.)



Have the same level of precedence



Applied from left to right



Used with conditions



Return the value true or false



Used only with a single condition

Logical Operators



Used to combine between multiple conditions



&& (logical

AND

)



true if both conditions are true

gender == 1 && age >= 65



|| (logical

)



true if either of condition is true

semester_Average >= 90 || final_Exam >= 90

condition

Logical Operators (cont.)



(logical

NOT

, logical negation)



Returns

true when its condition is false, and vice versa

!( grade == sentinelValue )

Also can be written as

grade != sentinelValue

Conditional operator (

)



Ternary operator requires three operands



Condition



Value when condition is

true



Value when condition is

false



Syntax

Condition

condition’s true value

condition’s false value

Examples

Can be written as

Can be written as .. ?

grade >= 60 ? cout<<“Passed” : cout<<“Failed”;

Example # 1

cout << (grade >= 60 ? “Passed” : “Failed”);

int

i = 1, j = 2, Max;

Max = ( i > j ? i : j );

Example # 2

bool

Variables in Expressions



false

is zero and

true

is any non-zero



The following codes applies implicit conversion between bool and
int

int

x = -10 ;

bool

flag = x ;

(true)

int

a = flag ;

// assign the value 1

int

b = !flag;

// assign the value 0

x = flag + 3;

// assign the value 4

cout << a << b << x;

On the screen: 1 0 4

Code # 1

Common Compilation Errors



Attempt to use % with non-integer operands



Spaces between pair of symbols e.g. (= =, ! =,

…etc)



Reversing order of pair of symbols e.g. =!



Confusing between equality (==) and assignment operator (=)

Exercise - 1

What is the output of the following program?

#include

<iostream>

2
3
4
5
6

int

main()

7 {
8

int

10      x = 30; y = 2;  z = 0;
11
12      cout << (++++x && z ) << endl;
13      cout << x * y + 9 / 3 << endl;
14      cout << x << y << z++ << endl;
15
16

return

17
18 }

// end main

What is wrong with the following
program?

int

main()

2 {
3

int

a,b,c,sum;

sum = a + b + c ;

return

6 }

Exercise - 2