Algorithm and Programming (Looping Structure)

Adam Mukharil Bachtiar
English Class
Informatics Engineering 2011
Algorithms and Programming
Looping Structure

Steps of the Day
Let’s Start
For Structure While Do
Structure
Repeat Until
Structure

WhyWeNeedLooping
Structure?
Make a program to showing “I LOVE
ALGORITHM” on the screen as much as 1000
times. WHAT WILL YOU DO?

WhatisLoopingStructure
An Algorithm structure that allow us to REPEAT
some statements that fulfill LOOPING CONDITION.

ComponentsinLooping
Structure
• Looping condition
• Body statement
• Initialization
• Termination

TypesofLoopingStructure
• FOR
• WHILE
• REPEAT

For Structure
Definition and Structures of For Structure

ForStructure
• For structure was used in looping that have
specified ending of repetition.
• Number of repetition have been known in
the beginning.
• Can be in ASCENDING or DESCENDING way

Format of For Structure (Ascending)
Algorithm Notation:
for variable  start_value to end_value do
statement
endfor
Pascal Notation I:
for variable := start_value to end_value do
statement;

Pascal Notation II:
for variable := start_value to end_value do
begin
statement;
end;

Example of For in Ascending Way (Algorithm)
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Algoritma Deret_Bilangan_Ganjil
{I.S: Diinputkan satu nilai akhir oleh user}
{F.S: Menampilkan jumlah deret ganjil}
Kamus:
x,akhir:integer
jumlah:integer
Algoritma:
input(akhir)
jumlah  0
for x  1 to akhir do
if x mod 2 = 1 then
jumlah  jumlah + x;
endfor
output(‘Jumlah deret ganjil dari 1 – ‘,akhir,’ = ‘,jumlah)

Example of For in Ascending Way (Pascal)
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program Deret_Bilangan_Ganjil;
uses crt;
var
x,akhir:integer;
jumlah:integer;
begin
write('Masukan batas akhir angka : ');readln(akhir);
jumlah:=0;
for x:=1 to akhir do
begin
if x mod 2=1 then
jumlah:=jumlah+x;
end;
writeln('Jumlah Deret ganjil dari 1 - ',akhir,' = ',jumlah);
writeln();
write('Tekan sembarang tombol untuk menutup...');
readkey();
end.

Format of For Structure (Descending)
Algorithm Notation:
for variable  end_value downto start_value do
statement
endfor
Pascal Notation I:
for variable := end_value downto start_value do
statement;

Pascal Notation II:
for variable := end_value downto start_value do
begin
statement;
end;

Example of For in Descending Way (Algorithm)
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Algoritma Deret_Faktorial
{I.S: Diinputkan satu nilai oleh user}
{F.S: Menampilkan faktorial dari bilangan tersebut}
Kamus:
i,nilai:integer
faktorial:integer
Algoritma:
input(nilai)
faktorial1
for i  nilai downto 1 do
faktorialfaktorial*i
endfor
output(nilai,’! = ‘,faktorial)

Example of For in Descending Way (Pascal)
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program Deret_Faktorial;
uses crt;
var
i,nilai:integer;
faktorial:integer;
begin
write('Masukan nilai = ');readln(nilai);
faktorial:=1;
for i:=nilai downto 1 do
faktorial:=faktorial*i;
writeln(nilai,'! = ',faktorial);
writeln();
readkey();
end.

While Structure

WhileStructure
• While structure always be executed while its
condition value is true.
• If the condition value is false, it means stop
repetition.
• While structure have condition in the
beginning of structure.

Format of While Structure
Algorithm Notation:
while kondisi do
statement
endwhile
Pascal Notation I:
while kondisi do
statement;

Pascal Notation II:
while kondisi do
begin
statement;
end;

Example of While (Algorithm)
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Algoritma Deret_Bilangan
{I.S: Diinputkan satu angka oleh user}
{F.S: Menampilkan jumlah deret dari 1 sampai angka}
Kamus:
i,deret:integer
angka:integer
Algoritma:
input(angka)
deret0
i1
while i<=angka do
deretderet+i
ii+1;
endwhile
output(‘Jumlah deret dari 1 – ‘,angka,’ = ‘,deret)

Example of While (Pascal)
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program Deret_Angka;
uses crt;
var
i,deret:integer;
angka:integer;
begin
write('Masukan angka = ');readln(angka);
deret:=0;
i:=1;
while i<=angka do
begin
deret:=deret+i;
i:=i+1;
end;
writeln('Jumlah deret dari 1 - ',angka,' = ',deret);
writeln();
readkey();
end.

Repeat Structure

RepeatStructure
• Repeat structure always be executed until its
condition value is true.
• If the condition value is true, it means stop
repetition.
• Repeat structure have condition in the end
of structure.

Algorithm Notation:
repeat
statement
until kondisi
Pascal Notation:
repeat
statement;
until kondisi;

Example of Repeat (Algorithm)
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Algoritma Coba_Password
{I.S: Diinputkan password oleh user}
{F.S: Menampilkan pesan benar atau salah}
Kamus:
const
password=1234
pass,i,j:integer
Algoritma:
i1
j3
repeat
input(pass)
if pass=password then
output(‘Password anda benar!’);
else
ii+1
jj-1
output(‘Password salah (‘,j,’ kali lagi)!’)
endif
until (pass=password)or(i=4)

Example of Repeat (Pascal)
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program Coba_Password;
uses crt;
const
password=1234;
var
pass,i,j:integer;
begin
i:=1;
j:=3;
repeat
write('Masukan password (',i,'): ');readln(pass);
if pass=password then
begin
writeln('Password anda benar!');
writeln();
writeln('Tekan sembarang tombol untuk menutup...');
readkey();
end
else
begin
i:=i+1;
j:=j-1;
writeln('Password salah (',j,' kali lagi)!');
readkey();
end;
clrscr();
until (pass=password)or(i=4);
end.

Exercise 1
Make the algorithm to solve this problem below (Color of
stars will be different each row):
N=5
*
* *
* * *
* * * *
* * * * *

Exercise 2
Make the algortihm to solve this problem below (Color of
stars will be different each row):
N=3
*
* *
* * *
* *
*

Exercise 3
Make algorithm to count:
s = 1 – 2/3 + 3/5 – 4/7+….

Exercise 4
Make algorithm to count the maximum value and
mean value from n students.

Contact Person:
Adam Mukharil Bachtiar
Informatics Engineering UNIKOM
Jalan Dipati Ukur Nomor. 112-114 Bandung 40132
Email: adfbipotter@gmail.com
Blog: http://adfbipotter.wordpress.com
Copyright © Adam Mukharil Bachtiar 2011

Algorithm and Programming (Looping Structure)

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