C Programming pdf - University of Mosul

University of Mosul

College of engineering

computer department

First class

•

C++ programming language

What Is Programming and Program Development Life
Cycle ?

• Programming is

a process of problem solving

• Step 1: Analyze the problem

– Outline the problem and its requirements
– Design steps (algorithm) to solve the problem

• Step 2: Implement the algorithm

– Implement the algorithm in code
– Verify that the algorithm works

• Step 3: Maintenance

– Use and modify the program if the problem domain changes

Algorithm

– Step-by-step problem-solving process

The Problem Analysis

–Coding–Execution Cycle

• Understand the Overall problem

• Understand problem requirements

– Does program require user interaction?
– Does program manipulate data?
– What is the output?

• If the problem is complex, divide it into subproblems

– Analyze each subproblem as above

The Problem Analysis

–Coding–Execution

Cycle (cont'd.)

• Run code through compiler

• If compiler generates errors

– Look at code and remove errors
– Run code again through compiler

• If there are no syntax errors

– Compiler generates equivalent machine code

• Linker links machine code with system resources

The Problem Analysis

–Coding–Execution

Cycle (cont'd.)

• Once compiled and linked, loader can place program into main memory

for execution

• The final step is to execute the program

• Compiler guarantees that the program follows the rules of the language

– Does not guarantee that the program will run correctly

The Language of a Computer

• Machine language:

language of a computer

• Binary digit (bit):

– The digit 0 or 1

• Binary code:

– A sequence of 0s and 1s

• Byte:

– A sequence of eight bits

The Evolution of Programming Languages

• Early computers were programmed in machine language

• To calculate wages = rates * hours in machine language:

100100 010001 //Load

100110 010010 //Multiply

100010 010011 //Store

The Evolution of Programming Languages

• Assembly language instructions are mnemonic

• Assembler: translates a program written in assembly language into

machine language

The Evolution of Programming Languages

• Using assembly language instructions, wages = rates • hours can

be written as:

LOAD rate
MULT

hour

STOR

wages

The Evolution of Programming Languages

• High-level languages include Basic, FORTRAN, COBOL, Pascal, C, C++,

C#, and Java

• Compiler

: translates a program written in a high-level language machine

language

• The equation wages = rate • hours can be written in C++ as:

wages = rate * hours;

The Problem Analysis

–Coding–Execution Cycle

Problem Analysis

Algorithm Design

Coding

Complier

Execution

Get Results

Errors

Using Any

Programming

Language

Translate Code

To Machine

Language

Then

Think

Write Code

Basic Definitions

• Programming language:

– a set of rules, symbols, and special words used to write computer

programs.

• Computer program

– Sequence of statements whose objective is to accomplish a task.

• Syntax:

– rules that specify which statements (instructions) are legal

Computer System

Input

Output

Processing

Operation

Oper

Example 1

• Write a program to find the Area of a rectangle

The area of the Rectangle are given by the following formula:

Area = Rect Length * Rect Width.

Input :

Rectangle Length , Rectangle Width.

Processing :

Area = Rect Length * Rect Width.

Output :

Print Out The area.

Example 2

• Write a program to find the perimeter and area of a square

The perimeter and area of the square are given by the following formulas:

perimeter = Side Length * 4

area = Side Length * Side Length

Input:

Square Side Length

Processing:

perimeter = Side Length * 4

area = Side Length * Side Length

Output:

Print Out The Perimeter and Area.

Your First C++ Program

#include

using namespace

std;

int

main()

{
  // This program is written by Mohamed El Desouki

cout << "My first C++ program." << endl;

return

}

Sample Run:

My first C++ program.

Processing a C++ Program (cont'd.)

•

To execute a C++ program:

– Use an editor to create a source program in C++

– Preprocessor directives begin with # and are processed by a the preprocessor

– Use the compiler to:

• Check that the program obeys the rules
• Translate into machine language (object program)

– Linker:

• Combines object program with other programs provided by the SDK to

create executable code

– Loader:

• Loads executable program into main memory

– The last step is to execute the program

Processing a C++ Program (cont'd.)

Interacting With User:

Displaying Messages on Screen

•

In C++ , we use Cout << “ Text To be Displayed on The screen “ ;

•

To use Cout << , we must use

– #include <iostream> ;
– using namespace std;

•

#include <iostream> notifies the

preprocessor

to include the contents of the

input/output

stream header file <iostream>

in the program

•

We can use the Escape Sequence to format the Displayed Text.

• We can put comment on our programs using

• //

to comment a single line

this progrm is written by mohamed

• /*

Mulitple Lines

• */

to comment multiple lines

This program is written by Mohamed

On Monday 11/1/2015

Interacting With User:

Comments

Example 1

• Write a program to find the Area of a rectangle

The area of the Rectangle are given by the following formula:

Area = Rect Length * Rect Width.

Input :

Rectangle Length , Rectangle Width.

Processing :

Area = Rect Length * Rect Width.

Output :

Print Out The area.

Central Processing Unit and Main Memory

Interacting With User:

Accept Input From User

• In C++ , we use Cin >> Variable; To accept an input from the user.
• To use Cin >>, we must use #include <iostream> ;

• #include <iostream> notifies the

preprocessor

to include in the program the

contents of the

input/output stream header file <iostream>

• A

variable

is a location in the computer’s memory where a value can be stored for

use by a program.

• All variables must be

declared

with a name and a data type before they can be

used in a program.

• Declaration

DataType Identifier;

Int width ;

Float salary ;

C++ Data Types

char

Character or small
integer.

1byte

signed: -128 to 127
unsigned: 0 to 255

int

Integer.

4bytes

signed: -2147483648 to 2147483647
unsigned: 0 to 4294967295

short int (short)

Short Integer.

2bytes

signed: -32768 to 32767
unsigned: 0 to 65535

long int (long)

Long integer.

4bytes

signed: -2147483648 to 2147483647
unsigned: 0 to 4294967295

bool

Boolean value. It can
take one of two values:
true or false.

1byte

true or false

float

Floating point number.

4bytes +/- 3.4e +/- 38 (~7 digits)

double

Double precision floating
point number.

8bytes +/- 1.7e +/- 308 (~15 digits)

long double

Long double precision
floating point number.

8bytes +/- 1.7e +/- 308 (~15 digits)

Working With Variable

Int  length ;
Int  width;
Int  area;

Cin>>Length;

Cin>>width;

Area =  Length * width ;

Length

Width

area

Example 2

• Write a program to find the perimeter and area of a square

The perimeter and area of the square are given by the following formulas:

perimeter = Side Length * 4

area = Side Length * Side Length

Input:

Square Side Length

Processing:

perimeter = Side Length * 4

area = Side Length * Side Length

Output:

Print Out The Perimeter and Area.

Declaring & Initializing Variables

• Initialization means to give a variable an initial value.

• Variables can be initialized when declared:

  int first=13, second=10;
  char ch=' ';
  double x=12.6;

• All variables must be initialized before they are used in an arithmetic

operatation

– But not necessarily during declaration

Rules on Variable Names

•

DO NOT use reserved words as variable names

(e.g. if, else, int, float, case, for, …).

•

The first character has to be a letter or underscore. It can not be a numeric digit.

•

The second and the other characters of the name can be any letter, any number, or
an underscore “

”.

Examples

Some valid names:

my_name, m113_1, salary, bluemoon , _at

Some invalid names:

my name, my-name , 1stmonth , salary! , guns&roses ,

Frequently used data types

Data Types Bytes Used

int

4 Bytes

short

2 Bytes

double

8 Bytes

unsigned

4 Bytes

Float

4 Bytes

Double

8 Bytes

Char

1 Byte

• The data type

unsigned

is used to represent positive

integers.

•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

Example :

-3738.7878787878

3.141592653589790

0.123456789123456

•

We can use

Scientific Notation

to represent real numbers that are very large or very small in

value.

•

The letters

is used to represent times

to the power.

Example:
•

1.23 x 10

is represented as 1.23e

or 1.23e

or 1.23E

•

1 x 10

-9

is represented as 1e

-9

Frequently used data types

Arithmetic Operations

Parentheses are used in C++ expressions in the same manner as in algebraic expressions.

For example, to multiply

times the quantity

b + c

we write

a * ( b + c ).

There is no arithmetic operator for exponentiation in C++,

is represented as

x * x

Precedence of arithmetic operations

For example,

2 + 3 * 5

and

(2 + 3) * 5

both have different meanings

Precedence of arithmetic operations

Example :

• ? =

1 + 2 * (3 + 4)

– Evaluated as

1 +

(2 *

(3+4)

)

and the result is

• ? =

5 * 2 + 9 % 4

– Evaluated as

(5*2)

(9 % 4)

and the result is

• ? =

5 * 2 % ( 7

– 4)

– Evaluated as

(5 * 2)

– 4)

and the result is

Precedence of arithmetic operations

Data Type of an Arithmetic Expression

• Data type of an expression depends on the type of its operands

– Data type conversion is done by the compiler

• If operators are *, /, +, or – , then the type of the result will be:

– integer, if all operands are integer.

» Int A , B;

» A+ B  Integer.

– float, If at least one operand is float and there is no double

» Int A ; Float B;

» A + B  Float.

– double, if at least one operand is double

• Int A ; Float B; Double C;

» A + B + C  double.

Data Type of an Arithmetic Expression

Example

int * int;

int + float;

Int + double / float;

int

– double;

result int

result float

result double

Data Type of an Arithmetic Expression

• The data type of the target variable is also important
• If the

result is a real number

and the

target variable is declared as

integer

, only the integer part of the result will be kept, and

decimal

part will be lost

Example

The result is calculated as
16.66667

But avg will be

int avg;

float sum=100.0, cnt = 6.0;
avg = sum / cnt;

Data Type of an Arithmetic Expression

The result of the division will be

avg will be

16.0

float avg;
int sum=100, cnt = 6;
avg = sum / cnt;

• Only the integer part of the result will be considered if two operands are integer

Even when the target variable is float

Type Casting

int main()
{
  int  i=5, j=3;
  float div;
  div= i/j;
  cout<< div;
}

The div will be

1.0

and this is not write

int main()
{
  int  i=5, j=3;
  float div;
  div=(

float

) i/j;

cout<< div;
}

Type cast

: tells the compiler to treat

as a

float

After type casting , The div will be

1.66667

Increment and Decrement Operators

• Increment operator:

increment variable by 1

– Pre-increment: ++variable
– Post-increment: variable++

• Decrement operator:

decrement variable by 1

– Pre-decrement: --variable
– Post-decrement: variable --

• Examples :

++K , K++ 

k= K+1

--K , K-- 

K= K-1

Increment and Decrement Operators

• If the value produced by ++ or – –

is not used in an expression

, it does

not matter whether it is a pre or a post increment (or decrement).

• When ++ (or – –) is used before the variable name,

the computer first

increments (or decrements) the value of the variable

and then uses its

new value to evaluate the expression.

• When ++ (or – –) is used after the variable name,

the computer uses the

current value of the variable

to evaluate the expression, and then it

increments (or decrements) the value of the variable.

• There is a difference between the following

x = 5;

Cout << ++x;

x = 5;

Cout << x++;

special assignment statements

• C++ has special assignment statements called compound

assignments

• Example:

X +=5 ; means

x = x + 5;

x *=y; means

x = x * y;

x /=y; means

x = x / y;

Control Statements

• Normally, statements in a program are executed one after the other in the order

in which they’re written.

• This is called

sequential execution

• There are control statements enable you to specify that the next statement to

be executed may be other than the next one in sequence.

• This is called

transfer of control

• The control statements are categorized in almost two groups:

 Selection control statements

 Repetition control statements

Sequential Execution

Transfer of Control

• Selection statements are used to choose among alternative courses of action.

• For example, suppose the passing mark on an exam is 60. The pseudocode

statement

– If student’s marks is greater than or equal to 60 Then

Print “Passed”

Selection Statements :

If Statement

if (

Expression

)

action statement ;

if ( Expression)
{
action statement 1 ;
action statement 2 ;
.
.
action statement n ;
}

In C++ , The syntax for the If statement

if ( grade >= 60 )
cout <<"Passed\n“;

•The

xpression

can be any valid

expression including a relational expression

and even arithmetic expression

•In case of using arithmetic expressions , a

non-zero

value is considered to be

true

whereas a

is considered to be

false

Relational Expression and Relational Operators

Operator Means

Equal To

Not Equal To

Less Than

Less Than or Equal To

Greater Than

Greater Than or Equal To

•

Relational expression is an expression which compares 2 operands and returns a
TRUE or FALSE answer.

Example : a >= b , a == c , a >= 99

, „A‟ > „a‟

•

Relational expressions are used to test the conditions in selection, and looping
statements.

Example

: write a program that accept an integer from the user and in case this

integer is even print out the following message

“This number is even “ .

Selection Statements :

If Statement

• The IF…Else selection statement allows you to specify that there is a course of

actions are to be performed when the condition is true and another course of
actions will be executed when the condition is false.

•

For example, the pseudocode statement

– If

student’s mark is greater than or equal to 60

Print “Passed”

else

Print “Failed”

Selection Statements :

If .. Else Statement

if ( Expression)

action statement ;

Else

action statement ;

if ( Expression)
{
action statements 1 ;
.
action statement n ;
}
Else
{
action statements 1 ;
.
action statement n ;
}

In C++ , The syntax for the If…Else statement

if ( grade >= 60 )
cout <<"Passed\n“;
Else
cout <<“Failed\n”

Example

: write a program that accept an integer from the user and

print out whether it is

Positive

Negative

number.

Selection Statements :

– else Statement

Nested If

• Nested If :

means to write an if statement within another if statement.

Example

: write a program that accept an integer number from the user ,

in case the number is

Positive

, check and print out whether it is

Even

Odd

number.

int main()
{
int number;
cout <<"Please Enter any number \n";
cin >>number;

if ( number >=0)

if (number % 2 == 0)

cout <<" This is an Even number \n";

else

cout <<"This is an Odd number \n \n";

}

– Else IF statement

• For example, write a program that ask the user to Enter 2 numbers and print out

whether they are equal or there is one which is greater than the other.

int main()
{

int num1, num2;
cout <<"Enter Number 1 , Number2 \n";
cin >>num1>>num2;

if ( num1 == num2 )

cout << "Both Are Equal \n";

else if (num1 > num2 )

cout <<"Number 1 is greater than number 2 \n";

else

cout <<"Number 2 is greater than number 1 \n";

}

– Else IF

• For example, the following code will print



for exam grades greater than or equal to



for grades greater than or equal to



for grades greater than or equal to



for grades greater than or equal to

, and



for all other grades

– if

( grade >=

)

cout <<

"A\n“

;

else if

( grade >=

)

cout <<

"B\n”

;

else if

( grade >=

)

cout <<

"C\n”

;

else if

( grade >=

)

cout <<

"D\n”

;

else

cout <<

"F\n“

;

Combining more than one condition

Operator

Means

Description

And

The Expression Value Is true If and Only IF both
Conditions are true

The Expression Value Is true If one Condition Is True

• To combine more than one condition we use the logical operators.

Example

check whether num1 is between 0 and 100

IF ( (num1 >= 0) && (num1 <=100) )

Cout

<<“The Number Is between 1 and 100” ;

Else

Cout

<<“ The Number Is Larger Than 100”;

Example, print out the student grade according to the following formulas:



for exam marks greater than or equal

and less than

equal 100 ,



for exam marks greater than or equal

and less than

90 ,



for exam marks than or equal to

and less than

80 ,



for exam marks than or equal to

and less than

70 ,



for all other marks

– if

( marks >=

marks <= 100)

cout <<

"A\n“

;

else if

(marks >=

80 &&

marks <90 )

cout <<

"B\n”

;

else if

(marks >=

70 &&

marks <80 )

cout <<

"C\n”

;

else if

(marks >=

60 &&

marks <70 )

cout <<

"D\n”

;

else

cout <<

"F\n“

;

Combining more than one condition

Example

: A company insures its Employees in the following cases:

– Employee is married.
– Employee is an Single male above 30 years of age.
– Employee is an Single female above 25 years of age.

– Conditions :

Marital status = „M‟;

Marital Status =„S‟ and Sex=„M‟ and Age >30

Marital Status =„S‟ and Sex=„F‟ and Age >25

Selection statements:

Switch Statement.

The switch control statement that allows us to make a decision from the number

of choices

Switch (

Expression

)

{

case

constant 1 :

Action statements;

break

;

case

constant 2 :

Action statements;

break

;

case

constant 3 :

Action statements;

break

;

default :

Action statements;

}

Expression

It could be an integer constant like

1, 2 or 3, or an expression that evaluates to an

integer .

Constant : is a specific value.

Switch (10);

Int i ;
Switch (i);

switch ( i + j * k )

switch ( 23 + 45 % 4 * k )

Switch (10.0);

float i ;
Switch (i);

switch ( i + j * k )

switch ( 23 + 45 % 4 * k )

Case 50:

Case 40 +10;

Case >= 50;
Case a+ b;

int i;
Cin>>I;
switch ( i )
{
case 10 :

Cout << "I am in case 1 \

n“ ;

break ;

case 20 :

Cout << "I am in case 2 \

n“ ;

break ;

case 30 :

Cout << "I am in case 3 \

n“ ;

break ;

default :
Cout << "I am in default \

n“ ;

}

char ch = 'x' ;

switch ( ch )
{
case 'v' :

Cout<< "I am in case v \

n“ ;

break ;

case 'a' :

Cout<< "I am in case a \

n“ ;

break ;

case 'x' :

Cout<< "I am in case x \

n” ;

break ;

default :
Cout<< "I am in default \

n„ ;

}

Expression Possible Forms

switch ( i + j * k )
switch ( 23 + 45 % 4 * k )

switch

(

grade

)

{

case

cout <<"You Got A \n"; break;

case

cout <<"You Got B \n"; break;

case

cout <<"You Got C \n"; break;

case

cout <<"You Got D \n"; break;

default :

cout <<" Sorry , You Got F \n";
}

( marks >=

marks <= 100)

cout <<

"A\n“

;

else if

(marks >=

80 &&

marks <90 )

cout <<

"B\n”

;

else if

(marks >=

70 &&

marks <80 )

cout <<

"C\n”

;

else if

(marks >=

60 &&

marks <70 )

cout <<

"D\n”

;

else

cout <<

"F\n“

;

Switch Versus IF

– Else IF

• There are some things that you simply cannot do with a switch. These

are:

– A float expression cannot be tested using a switch
– Cases can never have variable expressions (for example it is wrong to

say case a +3 : )

– Multiple cases cannot use same expressions.

– switch works faster than an equivalent IF - Else ladder.

Control Statements : Repetition statements

• Some times we need to repeat a specific course of actions either a

specified number of times or until a particular condition is being satisfied.

• For example :

– To calculate the Average grade for 10 students ,
– To calculate the bonus for 10 employees or
– To sum the input numbers from the user as long as he/she enters

positive numbers.

• There are three methods by way of which we can repeat a part of a

program. They are:

– (a) Using a while statement
– (b) Using a do-while statement
– (C) Using a for statement

1- The While Loop

1- loop counter is any numeric variable ( int

, float ,….).

2- when using a counter , the while loop is called

counter

–controlled loop.

3- The initial value of the loop counter is up to you,

but you have to increment it to avoid endless loops.

While ( continuation condition)
{

Action statement 1 ;
Action statement 2 ;

.
.

Action statement n ;
}

1- The While Loop

The condition being tested
may be relational, logical or
even numeric expression :

while ( i <= 10 )

while ( i >= 10 && j <= 15 )

While (3) , While (3 + 5)

• Example

: Write a program that calculates and prints out the Average

grade for

students .

int counter = 1;

int grade=0 , sum=0;

while (

counter <=6

)

{

cout <<"Enter grade for student no " << counter <<"\n";

cin >>grade;

sum += grade;

counter ++;

}

cout <<"Average Grade is " << sum/counter <<"\n";

1- The While Loop

• Example

: Write a program To print out the sum of the numbers entered

from the user as long as he/she enters positive numbers.

int number=0 , sum=0;

while (

number >= 0

)

{

cout <<" Enter Positive numbers to sum \n";

cin>>

number

;

sum += number;

}

Cout <<“ sum = “ << sum <<“\n”;

1- The While Loop

• Example

: Write a program To print out the sum of the numbers entered

from the user as long as he/she enters positive numbers.

int number=0 , sum=0;

cout <<" Enter Positive numbers to sum \n";

cin>>number;

while (

)

{

sum += number;

cout <<" Enter Positive numbers to sum \n";

cin>>

number

;

If (number < 0)

break;

}

1- The While Loop

• Example

: Write a program that calculates and prints out the Average

grade for

students or ends the program by entering -1.

int grade=0, counter =1, sum=0;

cout <<" Enter 5 grades or -1 To Exit \n";

while (counter <=5

grade !=-1)

{

cin>>grade;

sum += grade;

counter ++;

}

cout <<"The sum of grades is " << sum <<"\n";

1- The While Loop

2- The do-while Loop

1- loop counter is any numeric variable ( int

, float ,….).

2- The initial value of the loop counter is up to you,

but you have to increment it to avoid endless loops.

3- The Loop Body is Executed at least one Time.

2- The do-while Loop

The condition being tested
may be relational, logical or
even numeric expression :

while ( i <= 10 )

while ( i >= 10 && j <= 15 )

While (3) , While (3 + 5)

• Example

: Write a program that calculates and prints out the Average

grade for

students .

int counter = 1;

int grade=0 , sum=0;

{

cout <<"Enter grade for student no " << counter <<"\n";

cin >>grade;

sum += grade;

counter ++;

}

while (

counter <=6

) ;

cout <<"Average Grade is " << sum/counter <<"\n";

2- The do-While Loop

Control Statements : Repetition statements

• Some times we need to repeat a specific course of actions either a

specified number of times or until a particular condition is being satisfied.

• For example :

– To calculate the Average grade for 10 students ,
– To calculate the bonus for 10 employees or
– To sum the input numbers from the user as long as he/she enters

positive numbers.

• There are three methods by way of which we can repeat a part of a

program. They are:

– (a) Using a while statement
– (b) Using a do-while statement
– (C) Using a for statement

3- The For Loop.

• For Loop is probably the most popular looping instruction.

• general form of for statement is

•

The for allows us to specify three things about a loop in a single line:

(a) Setting a loop counter to an initial value.

(b) testing the loop counter to detect whether its value reached the number

of repetitions desired.

within the loop has been executed.

• Example

: Write a program that calculates and prints out the Average

grade for

students .

int grade=0, sum=0;

for (int counter =1 ; counter <=6 ; counter ++)

{

cout <<"Enter Grade \n";

cin>>grade;

sum += grade;

}

cout <<"

The Average grades is

“ << sum/6 <<"\n";

3- The For Loop.

int counter = 1;
int grade=0 , sum=0;
while (

counter <=6

)

{
cout <<"Enter grade for student \n“ ;
cin >>grade;
sum += grade;

counter ++;

}
cout <<"Average Grade is "
<< sum/6 <<"\n";

• Example

: Write a program that prints out numbers from

;

for (int i= 0 ; i <=10 ; i++)

cout << i << "\n“;

• Example

: Write a program that prints out the even numbers from

;

for (int i = 2 ; i <=20 ; i+=2 )

cout << i << "\n“;

3- The For Loop.

• Example

: Write a program that prints out numbers from

10 in

descending order

;

for (int i = 10 ; i >=0 ; i-- )

cout << i << "\n“;

• Example

: Write a program that accepts 10 numbers from the user and

prints out the sum of even numbers and the sum of odd numbers.

3- The For Loop.

int i = 1 ;

for ( ; i <= 10 ; i + + )

cout<< i ;

int i = 1 ;

for ( ; i <= 10 ; )

{

cout<< i ;

i ++;

}

int i ;

for ( i = 0 ; i++ < 10 ; )

cout<< i ;

int i ;

for ( i = 0 ; ++ i < 10 ; )

cout<< i ;

3- The For Loop.

• Example

: Write a program that calculates the Factorial for any given

positive number.

: Factorial (5) = 5 * 4 * 3 * 2 * 1

int number, factorial=1;

cout <<"Enter a positive number\n";

cin >> number;

if (number < 0 )

cout <<" Enter Positive Numbers only\n";

else

for (int i= 1 ; I <=number ; i++)

factorial = factorial * i;

cout <<" Factorila = “ << factorial <<"\n";

3- The For Loop.

Nested Loops

• Example

: Write a program that calculates the Factorial for numbers from

;

for ( int number=1; number<=10 ; number++)

{

for ( int i= 1 ; i <=number ; i++)

{

factorial = factorial * i ;

}

cout <<" Factorila of " << number <<"=" << factorial <<"\n";

}

*
**
***
****
*****
******

• Example

: Write a program that prints out the following pattern.

Nested Loops

for (int i = 1; i <= 5; i++)

{

for (int j = 1; j <= i ; j++)

cout << "*";

cout << endl;

}

Functions

• Most computer programs that solve real-world problems include hundreds and even

thousands of lines.

• Experience has shown that the best way to develop and maintain a large program is

to construct it from smaller pieces or

modules

, each of which is more manageable

than the original program.

• This technique is called

divide and conquer

• A Function :

is a self-contained block of statements that perform a specific

task.

• using a

function

is something like hiring a person to do a

specific job

for

you.

Task 1

Task 2

Task 3

Task 4

Function ( )

In Real Life

In Programming

Why to use Functions ?

• Functions

allows to write more manageable units of code.

• Writing functions

avoids rewriting

the same code over and over.

• Easy

maintenance

for programs.

Important Tips

Don‟t

try to cram the entire logic in one function. It is a very bad style of

programming.

Instead,

break a program into small units and write functions for each of these

isolated subdivisions.

Don‟t

hesitate to write functions that are called only once.

Task 1

Task 2

Task 3

Task 4

Get_Marks( )

Calc_sum( )

Calc_Average ( )

Print_out ( )

Calculate and print out The

sum and the Average of 3

student marks.

Functions

Function Definition

return-value-type

function-name(

parameter-list

)

{

Lines of code to be
executed
…
…
…
(Body)

}

Parameter-List

: Is a list of

data  values  supplied  from
the  calling  program  as
input  to  the  function.  It  is

Optional

return-value-type

Is the data type for the
returned

value

from

the

function

the

calling

program. It is

Mandatory,

no returned value expected
, we use keyword

Void.

Function Types

1. Built in Functions (Ready Made).

• For Example : Math Library Functions <cmath> Like

Built in Functions

int

abs

(int

number

) ;

double

pow

(double

base

, double

exponent

) ;

Double

floor

(double

number

);

Double

sqrt

(double

number

);

To correctly use the built in functions we must know well its header (prortotype).

return-value-type

function-name(

parameter-list

)

#include <iostream>

#include <cmath>

using namespace std;

int main ( )

{

int i = -5 ;

double x = 5.0;

double y = 2.0;

double z = 5.21;

cout << "The absolute value of i is " <<

abs (i)

<< "\n \n";

cout << "The power of x to the power y is " <<

pow (x,y)

<< "\n \n";

cout << "The Floor for Z is " <<

floor (z)

<<"\n \n";

cout << "The Ceil for Z is " <<

ceil (z)

<<"\n \n";

}

Function Types

2. User Defined Functions ( Tailored by Programmers).

Working with user defined functions is done in three steps :

1- Function declaration (

Prototype

, in C++ written before Main ( ) ).

2- Function Definition (

Body

, in C++ written After Main ( ) ).

3- Invoking Function (

Calling

, From The Main ( ) ).

Building Functions

1- Function Declaration (Written before The main( ) )

return-value-type

function-name(

Formal

parameter-list

)

2- Function Definition (Written after The main( ) )

return-value-type

function-name(

Formal

parameter-list

)

{

Lines of code to be
executed

}

3- Invoking Function ( From The main( ) )

Function name (

Actual Parameter- List

);

Formal Parameter-List

Is a list of input parameters
with their data types .

Int abs (

int

);

Actual Parameter-List

: Is a

list

input

parameters

without their data types .

Cout << abs (

);

User-Defined Functions

• Value-returning functions: have a return type

– Return a value of a specific data type using the return statement
– the returned value can be used in one of the following scenarios:

• Save the value for further calculation

Int result;
Result = sum ( x , y );

• Use the value in some calculation

Result = sum(x , y) /2;

• Print the value

Cout << sum(x , y);

• Void functions: do not have a return type

– Do not use a return statement to return a value

Flow of Execution

• Execution always begins at the first statement in the function main

• Other functions are executed only when they are called

• Function prototypes appear before any function definition

– The compiler translates these first

• The compiler can then correctly translate a function call

Flow of Execution (cont'd.)

• A function call results in transfer of control to the first statement in the

body of the called function

• After the last statement of a function is executed, control is passed back

to the point immediately following the function call

• A value-returning function returns a value

– After executing the function the returned value replaces the function

call statement

• For Example

: write a program that ask the user to Enter 2 integer numbers

and print out the larger of them.

int larger (int num1 , int num2);

int main ()

{

int n1 , n2 , result;

cout <<"Please Enter 2 integer numbers \n";

cin >>n1 >> n2;

result = larger(n1,n2);

cout <<" The Larger number is " << result<<"\n";

}

int larger (int num1 , int num2)

{

int max;

if (num1 >= num2)

max = num1;

else

max = num2;

return max;

}

For Example:

Write a program to calculate the Area and volume for a sphere.

– The area of sphere = 4 * PI * Radius * Radius .

– The Volume of sphere = 4/3 * PI * Radius

Radius * Radius .

– Note :

PI = 3.14

For Example

: write a program that ask the user to Enter 3 integer numbers

and print out their sum and Average.

int sum (int num1 , int num2, int num3);

float average (int num1,int num2, int num3 );

int main ()

{

int n1 , n2 , n3 ;

cout <<"Please Enter 3 integer numbers \n";

cin >>n1 >> n2 >> n3;

cout <<" The sum of the 3 number is " <<

sum (n1, n2,n3)

<<"\n";

cout <<" The average of the 3 number is " <<

average (n1, n2,n3)

<<"\n";

}

int sum (int num1 , int num2, int num3)

{

return num1+num2+num3;

}

float average (int num1, int num2, int num3 )

{

return sum (num1 , num2 , num3)/3;

}

100

Function Parameter‟s Default Value

int sum (int num1 , int num2, int

num3 = 90

);

int main( )

{

int n1 , n2 ;

cout <<"Please Enter 3 integer numbers \n";

cin >>n1 >> n2 ;

cout <<" The sum of the 3 number is " <<

sum (n1, n2)

<<"\n";

}

int sum (int num1 , int num2, int

num3 = 90

)

{

return num1+ num2+ num3;

}

Function Parameters Types

101

• Value parameter

Reference parameter

– The value parameter has its own copy of the data

– During program execution, The value parameter manipulates the data

stored in its own memory space.

the actual parameter not Affected

with any change.

void swap( int x, int y )

{

int temp;

temp= x;

x = y;

x = temp;

}

Temp

•

Reference parameter

– A reference parameter stores the address of the corresponding actual parameter

– During program execution to manipulate data, The address stored in the

reference parameter directs it to the memory space of the corresponding actual

parameter

• Reference parameters are useful in three situations:

– Returning more than one value

– Changing the actual parameter

– When passing the address would save memory space and time

102

Function Parameters Types

103

Function Parameters Types

void swap( int &x, int &y )

{

int temp;

temp= x;

x = y;

x = temp;

}

Scope of a variable

scope

is the context within a program in which a variable is valid and

can be used.

– Local variable

: declared within a function (or block)

– can be accessible only within the function or from declaration to the end of the

block.

– Within nested blocks if no variable with same name exists.

104

int main ( )

{

Int x ;

}

int sum (int x , int y )

{

int result ;

result = x + y;

return result;

}

Scope of a variable

Global variable

: declared outside of every function definition.

– Can be accessed from any function that has no local variables with the same

name. In case the function has a local variable with the same name as the
global variable ,

105

Int z ;

int main ( )

{

}

int sum (int x , int y )

{

}

106

int

= 100 ;

int main ( )

{

int

= 10;

int y = 50;

cout << " Global X" <<

::x

<< " Main

" <<

<< " " << y;

{

int z ,

;

z=100;

y=100;

x= 250;

cout <<" inner block " <<

;

}

Scope of a variable

107

• Using global variables causes side effects

– A function that uses global variables is not independent

– If more than one function uses the same global variable and something goes

wrong ,

– It is difficult to find what went wrong and where Problems caused in one area

of the program may appear to be from another area.

– To prevent the global variable to be modified use the

Const

Keyword.

Const

float

pi = 3.14

;

Scope of a variable

Static and Automatic Variables

• Automatic variable:

– memory is allocated at block entry and de-allocated at block exit
– By default, variables declared within a block are automatic variables

108

int issue_ticket (int x , int y )

{

int ticket_no = 0;

cout <<"Flight No : " <<flight_no <<"\n";

cout <<"Ticket no : " << ++ ticket_no <<"\n";

cout <<"Issued For: " << pname <<"\n \n \n";

}

Ticket No

Static and Automatic Variables

• Automatic variable:

– memory is allocated at block entry and de-allocated at block exit
– By default, variables declared within a block are automatic variables

• Static variable:

– memory remains allocated as long as the program executes
– Variables declared outside of any block are static variables
– Declare a static variable within a block by using the reserved word

static .

Static

int

;

109

Arrays

• Array : is a collection of fixed number of elements, wherein all

of elements have same data type.

• Array Basics:

– Consecutive group of memory locations that all have the same type.

– The collection of data is indexed, or numbered, and at starts at 0 and

The highest element index is one less than the total number of
elements in the array.

• One-dimensional array:

– elements are arranged in list form.

• Multi-dimensional array:

– elements are arranged in tabular form.

110

• Syntax for declaring a one-dimensional array:

Datatype

ArrayName

[

ArraySize

] ;

ArraySize

: any positive integer or constant variable.

111

• Example:

int num[5];

Arrays

• Example:

const

int

size = 5

;

int num[

size

];

num

• Accessing array Elements

Arrayname

[

element index

Arrays

•

Example:

int list[

];

list[

] = 34;

Cout << list [

];

112

113

Array Initialization

• Consider the declaration

int list[10]; //array of size 10

• After declaring the array you can use the For .. Loop to initialize it with

values submmited by the user.

• Using

for

loops to access array elements:

for (int i = 0; i < 10; i++)

//process list[i]

• Example:

for (int i = 0; i < 10; i++)

cin >> list[i];

• Example

Write a program that ask the user to enter 10 Employee

salaries and store them , then add a bonus of 10 % for each
employee and print out the average salary value.

114

• Arrays can be initialized during declaration

– In this case, it is not necessary to specify the size of the array

• Size determined by the number of initial values in the braces

• Example 1:

int Items

[]

{

12, 32, 16, 23, 45

}

;

• Example 2:

int

items

[10] = {

};

• Example 3: int

items [10] = {

5, 7, 10

};

115

Array Initialization

int

Arr1

[5]

;

int

Arr2

[ 5 ] ;

Arr1 =

Arr2

;

116

Array Initialization

117

Array as a Parameter to Function

• Arrays are passed by reference only
• The symbol & is not used when declaring an array as a formal parameter
• The size of the array is usually passed as a parameter to the function.

Float calc_Average ( Float marks [ ] , int size )
{
float sum =0 ;

for (int I =0 ; I <size ; I ++)
  Sum += marks [ I ] ;

return sum / size;
}

•

We may add keyword

const

before array name to

Prevent the function from modifying the array elements.

Float calc_Average (

const

Float marks [ ] , int size )

118

bool find_Item( int list[ ] , int searcheditem , int size)
{
int  indx;
bool  found = false;

for ( indx = 0 ; indx < size ; indx++)
if (list[indx] == searcheditem)
{
   found =true ;
   break ;
}
     return found;
}

• Example

Write a program that uses a function to search for an

item within an array.

Two Dimensional Array

• Used when data is provided in a table form.
• For Example , to store 4 Marks for 6 students.

119

M 1

Student 1

Student 2

Student 3

Student 4

Student 5

Student 6

120

• Two dimensional Array declaration

Datatype

ArrayName

[ Rows] [Columns] ;

Example :

Float marks [6] [4] ;

marks [4][2]= 20 ;

121

Two dimensional Array Initialization

• Consider the declaration

float marks[6][4];

• After declaring the array you can use the For .. Loop to initialize it with

values submmited by the user.

• Using 2 nested

for

loops to access array elements:

for (int row = 0; row < 6; row++)

for (int col = 0; col < 4; col++)
cin >> marks[ row ][col];

• Two dimensional Arrays can be initialized during declaration

• Example 1:

float marks

[4][3]

{{20,30,35},

  {40,45,65},
  {60,65,75},
  {80,65,45}}

;

122

Two dimensional Array Initialization

123

• Example

Write a program that build a matrix of 5 rows and 3

columns . As the use to enter the values for all the matrix items ,
print out the

sum of all matrix items

and print out the

sum of the

diagonal items.

void printMatrix( int matrix[ ][

], int Rows)

  {
     int row, col;
     for (row = 0; row < Rows ; row++)
   {
   for (col = 0; col < 4; col++)
     cout << setw(5) << matrix [row] [col] ;
   }
     cout <<“\n” ;
}

124

when declaring a two-dimensional array as a formal parameter, you can omit

the size of the first dimension, but not the second;

that is, you must specify the number of columns.

Two dimensional Array as a Parameter to

Function

Struct

• Struct

: collection of a fixed number of components (members),

accessed by name

– Members may be of different types.

– For Example :

to store a student record which includes different data

items like (student_no , Fname, Lname , Total_Marks

, GPA , …….).

– Syntax for Defining Struct is :

125

Struct

struct_name

{

Datatype  identifier 1;
Datatype  identifier 2;
.
.
.
Datatype  identifier n;

} ;

• For Example

: To store an Employee data like (

emp_no , fname , lname ,

salary , bonus , net_salary

);

126

Struct   Employee
{
int   emp_no ;
string   fname ;
string   lname;
float   salary;
float   bonus ;
float   net_salary;
} ;

Struct

• Once , a new struct is defined , we can use it as any other data type.

127

struct Employee

{

int       emp_no ;
string   fname ;
string   lname;
float    salary;
float   bonus ;
float   net_salary;

} ;

int main ()
{

Employee emp1 , emp 2;

}

Emp 1

Emp_no :

Fname :

Lname :

Salary :

Bonus :

Net_salary :

Emp 2

Emp_no :

Fname :

Lname :

Salary :

Bonus :

Net_salary :

Struct

To Access the Memebers of the struct , use the

Operator

128

struct Employee

{

int       emp_no ;
string   fname ;
string   lname;
float   salary;
float   bonus ;
float   net_salary;

} ;

int main ()
{

Employee emp1;
emp1

emp_no = 12;

emp1

fname="Ahmed";

emp1

lname="Ali";

emp1

salary=3000;

emp1

bonus=500;

emp1

net_salary= emp1.salary + emp1.bonus;

}

Emp 1

Emp_no :

Fname :

Lname :

Salary :

Bonus :

Net_salary :

Ahmed

Ali

3000

500

3500

Assignment and Comparison

Value of one struct variable can be assigned to another struct variable

of the same type using an assignment statement

Example :

Employee emp1 , emp2 ;

emp2 = emp1;

copies the contents of

emp1

into

emp2

;

129

• Compare struct variables member-wise

– No aggregate relational operations allowed

• To compare the values of

emp1

and

emp2

if ( emp1.emp_no

emp2.emp_no &&

emp1.fname

emp2.fname && emp1.salary

emp2.salary )

{

}

struct Variables and Functions

• A

struct

variable can be passed as a parameter by value or by reference.

• A function can return a value of type

struct

130

struct distance_type
{
Int feet ;
float inches;
};

distance_type

Add_distances

(distance_type d1 , distance_type d2 );

int main ()
{
}

distance_type

Add_distances

(distance_type d1 , distance_type d2 )

{
distance_type result;
result.feet = d1.feet + d2.feet;
result.inches = d2.inches + d2.inches ;
return result;
}

131

Arrays in structs

struct Student

{

int       student_no ;
string   sname ;
float   GPA;
float   marks[3];

} ;

int main ()
{

Student s1;
s1

student_no = 120;

sname="Ahmed Ibrahim";

GPA= 3.56;

s1.marks[0] = 80;
s1.marks[1] = 70;
s1.marks[2] = 90;

}

132

structs in Arrays

struct Employee

{

int       emp_no ;
string   fname ;
string   lname;
float   salary;
float    bonus ;
float   net_salary;

} ;

int main ()
{

Employee arr[5];
arr[0]

emp_no = 12;

arr[0]

fname="Ahmed";

arr[0]

lname="Ali";

arr[0]

salary=3000;

arr[0]

bonus=500;

arr[0]

net_salary= arr[0].salary + arr[0].bonus;

}

structs within a struct

133



Revision

• Write a program that used to manage The HR data of a department

that has a team of 5 employees .

The employee data like ( eno , ename

, job ,salary , bonus)

. The program should have

Function to accept the data of employees and automatically set the
salary according to the following formulas In case the

job = „Manager‟  salary = 5000

job = „Engineer‟  salary        = 3000
job = „Clerck‟  salary            =  2000
Otherwise    salary              =  1000

2. Function to set the bonus value for a specific employee

according to specific percent.

3. Function to print out the data of all employees.

134