Chapter 7 Loops - ftms.edu.my€¦ · DO-WHILE Loop • Like a while loop, a do-while loop is a...

PROG0101 Fundamentals of Programming

PROG0101

FUNDAMENTALS OF PROGRAMMING

Chapter 7

Topics

• Loops

• Condition Tested Loops

• Counted Loops

• Endless Loops

• FOR Loop

• WHILE Loop

• DO-WHILE Loop

• A loop is a sequence of instructions that is continually

repeated until a certain condition is reached.

• Loops allow for the same statement to be executed a

number of times in succession.

Pseudocode:

Do Something

Until Condition

Flowchart:

Condition

Do something

• There are three types which are common to most

programming languages:

– Condition Tested Loops

– Counted Loops

– Endless Loops

Condition Tested Loops

• A condition tested loop is one which repeats a set of

instructions until a certain condition is reached.

• The test can be performed at the start of the loop

(before any of the instructions are executed), during

the loop, or at the end of the loop.

• Usually, the condition will be testing the result of

executing the statements that are inside the loop.

Counted Loops

• A counted loop is one which allows the programmer

to instruct the computer to perform a set of

instructions x times, where x is usually an integer

value, but some programming languages offer other

data types.

• One could argue that the counted loop is just a

condition tested loop which updates a counter and

exits once a given value is reached.

Counted Loops

• The only time to use a count loop is when the

program can determine ahead of time how many

times the loop will repeat.

• There are generally two ways that the number of

repetitions of a loop will be know ahead of time:

– The loop always repeats the same number of

times.

– The program calculates the number of repetitions

based upon user input.

Endless Loops

• An endless loop goes round and round until one of

three things happens:

– The computer is turned off (or the application

stopped, forcefully)

– The computer encounters an EXIT (or similar)

statement

– An error forces the application to 'crash'

• Some endless loops serve a purpose, in message

loops, for example, where it is necessary to

continually monitor for incoming messages from the

operating system.

Example of Loop Statement

• These are examples loop statement in programminglanguage

– FOR Loop

– WHILE Loop

– DO … WHILE Loop

FOR Loop

• A FOR loop is a loop that repeats a specified numberof times.

• The loop uses a counter to tell it how many times torun the same sequence of activities.

FOR Loop

• The counter has the following three numeric values:

– Initial counter value

– Increment (the amount to add to the counter eachtime the loop runs)

– Final counter value

• The loop ends when the counter reaches the finalcounter value, or, if there is an associated testcondition, when the test condition is true.

FOR Loop

Condition

(Final

counter)

Do something

Initial value

Increment

Pseudocode:

FOR x times

Do Something

Increment

Flowchart:

FOR Loop

FOR loop syntax:

FOR (initial counter value, final counter, increment)

Statement (Do Something)

FOR Loop

Example 1:

FOR (x=1, x<5, x++)

PRINT “Hello World”

Output:

Hello World

FOR Loop

Example 2:

FOR (x=1, x<=4, x++)

PRINT x

Output:

FOR Loop

Example 3:

FOR (x=5, x>0, x--)

PRINT x

Output:

WHILE Loop

• A WHILE loop is a loop that repeats while some

condition is satisfied.

• The WHILE loop tests its condition at the beginning of

every loop.

• If the condition is false from the start, the sequence of

activities contained in the loop never runs at all.

Flowchart:

WHILE Loop

Condition

Do something

Pseudocode:

WHILE condition

Do SomethingFalse

WHILE Loop

WHILE loop syntax:

WHILE (Condition)

Statement (Do Something)

WHILE Loop

Example 1:

WHILE (x < 5)

Output:

Hello World

WHILE Loop

Example 2:

WHILE (key != Esc)

Output:

Hello world

DO-WHILE Loop

• Like a while loop, a do-while loop is a loop that

repeats while some condition is satisfied.

• Unlike a while loop, a do-while loop tests its condition

at the end of the loop.

• This means that its sequence of activities always runs

at least once.

DO-WHILE Loop

Flowchart:

Condition

Do something

Pseudocode:

something

WHILE condition

DO-WHILE Loop

DO-WHILE Loop Syntax

Statement

WHILE (Condition)

DO-WHILE Loop

Example 1:

WHILE (x<5)

Output:

Hello World

DO-WHILE Loop

Example 2:

WHILE (x>5)

Output:

Hello World

DO-WHILE Loop

Example 3:

WHILE (Key != Esc)

Output:

Hello World

Exercise

Draw flowchart diagram for the following programs using

1. A program that display number 1 to 20

2. A program that display a person name x times.

Chapter 7 Loops - ftms.edu.my€¦ · DO-WHILE Loop • Like a while loop, a do-while loop is a...

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