Algoritma dan Flowchart - anggafanani.lecture.ub.ac.idanggafanani.lecture.ub.ac.id/files/2014/10/Algoritma-dan-Flowchart... · Algoritma dan Flowchart Angga Akbar Fanani 1 Problem

04/10/2014

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Algoritma dan FlowchartAngga Akbar Fanani

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Problem

• Pertanyaan atau tugas yang kita cari jawabandan/atau penyelesaiannya

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We "just do" Guesswork-and-luck

Experience (possibly

someone else's)

Trial-and-error Scientifically"

HOW DO WE SOLVE PROBLEMS?

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The Problem-solving Process

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Problem specification

Algorithm

Program

Executable (solution)

Design

Implementation

Compilation

Analysis

The Problem-solving Process

Problem specification

Algorithm

Program

Executable (solution)

Analysis

Design

Implementation

Compilation

“Doctor, my head hurts“

Patient has elevated pressure in anterior parietal lobe

1. Sterilize cranial saw2. Anaesthetize patient

3. Remove top of skull4. Get the big spoon...5. etc., etc.

sterilize(saw,alcohol);raise_hammer();lower hammer(fast);start(saw);/* etc. etc. */0100111010110010101010101001010101010100

11001010101010100101101001110101010101

001001011101001111010101011111010101000110100001101...

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Definisi Algoritma

• Algoritma adalah urutan langkah logis tertentu untuk memecahkan suatu masalah▫ Urutan langkah logis, yang berarti algoritma harus

mengikuti suatu urutan tertentu, tidak boleh melompat-lompat

• Alur pemikiran dalam menyelesaikan suatu pekerjaan yang dituangkan secara tertulis.▫ Alur pikiran, sehingga algoritma seseorang dapat

juga berbeda dari algoritma orang lain▫ Tertulis, yang artinya dapat berupa kalimat,

gambar, atau tabel tertentu

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Definisi Algoritma

• Deretan langkah-langkah komputasi yang mentransformasikan data masukan menjadi keluaran

• Deretan instruksi yang jelas untuk memecahkan masalah, yaitu untuk memperoleh keluaran yang diinginkan dari suatu masukan dalam jumlah waktu yang terbatas

• Prosedur komputasi yang terdefinisi dengan baik yang menggunakan beberapa nilai sebagai masukan dan menghasilkan beberapa nilai yang disebut keluaran.

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Sejarah Algoritma

• Asal kata algoritma berasal dari nama Abu Ja’far Mohammed Ibn Musa al-Khowarizmi▫ Ilmuan Persia yang menulis kitab al jabar wal-

muqabala (the book of restoration and reduction)▫ Tahun 825 M

• Perubahan kata▫ Algorism proses menghitung dengan angka Arab▫ Algorist orang yang menggunakan angka Arab▫ Algorithm metode perhitungan secara umum

• Tahun 1950 euclid’s algorithm▫ Langkah-langkah menemukan pembagi bersama

terbesar (common greatest divisor = gcd)

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Ciri Algoritma (Donald E. Knuth)

• Finiteness: Algoritma harus berhenti setelah mengerjakan sejumlah langkah terbatas

• Definiteness: Setiap langkah harus didefinisikan secara tepat dan tidak berarti-dua (ambiguous)

• Algoritma memiliki nol atau lebih masukan (input)

• Algoritma memiliki nol atau lebih keluaran (output)

• Effectiveness: Algoritma harus efektif, setiap langkah harus sederhana sehingga dapat dikerjakan dalam sejumlah waktu yang masuk akal

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Algorithm -- Examples

• A cooking recipe• Assembly instructions for a model• The rules of how to play a game• VCR instructions• Description of a martial arts technique• Directions for driving from A to B• A knitting pattern• A car repair manual

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Almond and Honey Slice

1/2 quantity Shortcrust Pastry

185 g unsalted butter

100 g castor sugar

5 tablespoons honey

50 ml cream

50 ml brandy or any other liqueur or spirit

300 g flaked almonds

Preheat oven for 200° C

Line a 30 cm 20 cm baking tray with baking paper, and then with pastry

Bake blind for 20 minutes, then remove weights and foil

Turn oven up to 220° C.

Bring remaining ingredients to a boil, stirring.

Spread evenly over pastry.

Bake until topping is bubbling and has caramelised evenly, about 15 minutes.

Cool before cutting into fingers or squares.

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From: Stephanie Alexander, The Cook’s Companion, Viking/Penguin, Ringwood, Victoria, 1996, p. 349.

Almond and Honey Slice

1/2 quantity Shortcrust Pastry

185 g unsalted butter

100 g castor sugar

5 tablespoons honey

50 ml cream

50 ml brandy or any other liqueur or spirit

300 g flaked almonds

Preheat oven for 200° C

Line a 30 cm 20 cm baking tray with baking paper, and then with pastry

Bake blind for 20 minutes, then remove weights and foil

Turn oven up to 220° C.

Bring remaining ingredients to a boil, stirring.

Spread evenly over pastry.

Bake until topping is bubbling and has caramelised evenly, about 15 minutes.

Cool before cutting into fingers or squares.

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From: Stephanie Alexander, The Cook’s Companion, Viking/Penguin, Ringwood, Victoria, 1996, p. 349.

Instructions are given in the order in which they are performed (“executed”)

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Correct Algorithm?Cut chicken into pieces

and brown the pieces on all sides in a casserole dish in hot olive oil.

Remove the chicken and to the juices in the casserole add garlic, onions and green peppers, and sauté until onion is golden.

Add bay leaf, whole tomatoes, and chicken broth.

When the broth boils add salt, saffron and rice.

Arrange chicken on rice, cover casserole and bake in a moderate oven (350°F) for 20 minutes or until the rice is tender.

Add beans and artichokes during last 10 minutes of cooking.

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From: “Arroz Con Pollo” in The Margaret Fulton Cookbook, Hamlyn, Sydney, 1968.






Arrange chicken on rice, cover casserole and bake in a moderate oven (350°F) for 20 minutes or until the rice is tender.

Add beans and artichokes during last 10 minutes of cooking.

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From: “Arroz Con Pollo” in The Margaret Fulton Cookbook, Hamlyn, Sydney, 1968.

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Arrange chicken on rice, cover casserole and bake in a moderate oven (350°F) for 10 minutes.

Add beans and artichokes.

Cover, and bake for another 10 minutes or until rice is tender.

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Correct algorithm ???...

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Correct algorithm

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Values

• Represent quantities, amounts or measurements

• May be numerical or alphabetical(or other things)

• Often have a unit related to their purpose

• Example:▫ Recipe ingredients

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Variables

• Are containers for values – places to store values

• Example:

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This jar

can contain

10 cookies

50 grams of sugar

3 slices of cake

etc.

ValuesVariable

Restrictions on Variables

• Variables may be restricted to contain a specific type of value

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Instructions (Primitives)

• Some action that is ▫ simple

▫ unambiguous

▫ that the system knows about...

▫ ...and should be able to actually do

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Instructions – Examples

• Take off your shoes

• Count to 10

• Cut along dotted line

• Knit 1

• Purl 2

• Pull rip-cord firmly

• Sift 10 grams of arsenic

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Directions to perform specific actions on valuesand variables

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Instructions -- Application

• Some instructions can only be applied to a specific type of values or variables

• Examples:

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Instructions (Primitives) --Recommendations• When writing an algorithm, make each

instruction simple and unambiguous

• Example:

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Cut chicken into pieces and brown the pieces on all sides in a casserole dish in hot olive oil.

Cut chicken into pieces.Heat olive oil in a casserole

dish.Brown the chicken pieces in

the casserole dish.

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Instructions (Primitives)

• When writing an algorithm, make each instruction simple and unambiguous

• Example:

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Cut chicken into pieces and brown the pieces on all sides in a casserole dish in hot olive oil.

Cut chicken into pieces.Heat olive oil in a casserole

dish.Brown the chicken pieces in

the casserole dish.

A “sequence” of simple instructions

Function

• A named sequence of instructions

• So that you can▫ Refer to it collectively (by name)

▫ ...instead of individually (by each instruction in the sequence)

• Example:

▫ Drive_To_Uni

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Function -- Examplefunction Drive_To_Uni{

1. find car keys2. disable car alarm3. open car door

4. get in car5. shut car door6. put keys in ignition7. start car8. back car out of

driveway9. drive to end of street

10. turn right11. drive to end of street12. turn left...etc...etc...etc

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...etc...etc...etc...52. find parking space53. pull into parking

space54. turn off engine55. remove keys from

ignition56. open car door57. get out58. shut car door59. lock car door60. enable alarm

}

Function – Example

function Do_Wednesday{

Wake_upHave_ShowerEat_BreakfastDrive_To_UniSit_1301_Lecture...etc...etc...etc...Drive_From_Uni...etc...etc...etc...

}

function Do_Week

{

Do_Monday

Do_Tuesday

Do_Wednesday

Do_Thursday

...etc...etc...etc...

}

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Components of an Algorithm

• Variables and values

• Instructions▫ Sequences

▫ Functions

▫ Selections

▫ Repetitions

Also required: Documentation

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Struktur dasar algoritma

Struktur Urut (Sequence),

Struktur Pemilihan (Selection),

Struktur Pengulangan (Repetition).

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Sequence

• A series of instructions

• ...to be carried out one after the other...

• ...without hesitation or question

• Example:

▫ How to cook a Gourmet MealTM

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Sequence -- Example

1. Open freezer door2. Take out Gourmet Meal™3. Close freezer door4. Open microwave door5. Put Gourmet Meal™ on carousel6. Shut microwave door7. Set microwave on high for 5 minutes8. Start microwave9. Wait 5 minutes10.Open microwave door11.Remove Gourmet Meal™12.Close microwave door

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Struktur Urut (Sequence)

• suatu struktur program dimana setiap baris program akan dikerjakan secara urut dari atas ke bawah sesuai dengan urutan penulisannya.

• instruksi baris program 2 akan dikerjakan jika instruksi baris program 1 telah selesai dikerjakan.

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Selection

• An instruction that decides which of two possible sequences is executed

• The decision is based on a single true/falsecondition

• Examples:

▫ Car repair

▫ Reciprocals

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Selection Example – Car Repairif (motor turns) then {

CheckFuelCheckSparkPlugsCheckCarburettor

}else {

CheckDistributorCheckIgnitionCoil

}

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Selection Example – Car Repair

if (motor turns) then {


}else {


}

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Should be a true or falsecondition

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}else {


}

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Sequence if the condition is true




}else {


}

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Sequence if the condition is false

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Struktur Pemilihan (Selection),

• Menghasilkan nilai benar (true) atau nilai salah (false).

• IF sederhana IF <syarat> THEN

<instruksi>

• Pada bentuk IF sederhana ini,

intruksi akan dikerjakan jika

syarat yangdiuji benilai benar (true). Jika syarat yang diuji benilai salah (false) maka tidak ada instruksi yang dikerjakan.

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IF … THEN … ELSE …• IF <syarat> THEN

<instruksi1>

ELSE

<instruksi2>

• Pada bentuk ini terdapat dua

kemungkinan pilihan yang

akan dikerjakan berdasarkan

hasil pengujian, jika syarat

yang diuji benilai benar maka instruksi1 yang dikerjakan, dan jika syarat yang diuji bernilai salah maka instruksi2 yang dikerjakan.

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IF Bersarang (Nested IF)

• IF <syarat1> THEN<instruksi1>

• ELSE IF <syarat2> THEN<instruksi2>

• ELSE IF <syarat3> THEN<instruksi3>

• ELSE IF <syaratm> THEN<instruksim>

• ELSE<Instruksin>

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Repetition

• Repeat an instruction...

▫ ...while (or maybe until) some true or false condition occurs

▫ Test the condition each time beforerepeating the instruction

• Also known as iteration or loop• Example:

▫ Algorithm for getting a date

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Repetition – Example

function AskOnDate ( name, time, location ){

Phone(name)Say("Hey", name, "it's your lucky day!")Say("Wanna come to", location, "at", time, "?")ListenToReply ( )start begging count at zerowhile (reply is "No" and begging count < 100){

Say("Oh please!")add 1 to begging count ListenToReply ( )

}}

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Repetition – Example (cont)


Phone(name)Say("Hey", name, "it's your lucky day!")Say("Wanna come to", location, "at", time, "?")ListenToReply ( )start begging count at zerowhile ( reply is "No" and begging count < 100 ){

Say("Oh please!")add 1 to begging countListenToReply ( )

}}

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Condition is tested before sequence

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}}

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Sequence may not get executed at all





}}

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Ensure initial values of variables used in the conditions are set correctly

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}}

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Ensure the variables used in the conditions are updated in each repetition




Say("Oh please!")}

}

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Infinite loop

• What if we don’t increment the begging count?

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Struktur pengulangan repetition

• Struktur for

• Mengulang satu baris instruksi atau satu blok instruksi sampai jumlah perulangan yang disyaratkan terpenuhi.

• Ciri utama terdapat nilai awal dan nilai akhir yang menunjukkan banyaknya pengulangan yang akan dilakukan.

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Struktur while• untuk mengulang satu baris instruksi atau

satu blok baris instruksi selama syarat yang diberikan masih terpenuhi.

• Syarat akan diuji didepan.

• Jika syarat yang diuji bernilai benar maka instruksi1, instruksi2, instruksi3 akan dikerjakan, setelah mengerjakan instruksi1, instruksi2, instruksi3 maka syarat akan diuji lagi.

• pengulangan akan berhenti jika syarat yang diuji bernilai salah.

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Struktur do … while

• mengulang satu baris instruksi atau satu blok baris instruksi sampai syarat tidak terpenuhi.

• syarat akan diuji dibelakang, sehingga baris instruksi yang masuk dalam blok do…while minimal akan dikerjakan satu sekali.

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Documentation

• Records what the algorithm does

• Describes how it does it

• Explains the purpose of each component of the algorithm

• Notes restrictions or expectations

• Example:▫ Getting a date (again)

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Documentation -- ExampleThink of something romantic to dodecide on time and location

Work through address book to look for a person

initialise booking to “unsuccessful”until (successfully booked){

get next Name in little black bookAskOnDate(Name, Time, Location)DetermineBookingSuccess

}

Assumes that I will find someone in the book before it runs out

SighWithRelief

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From Algorithms to Programs

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Problem

ProgramProgram

AlgorithmAlgorithm: A sequence of instructions describing how to do a task (or process)

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The Software Development Process

• Define the problem clearly

• Analyse the problem thoroughly

• Design an algorithm carefully

• Code the algorithm efficiently

• Test the code thoroughly

• Document the system lucidly

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Top-down Algorithm Design

• Write down what you have to do

• Break that into 3-7 smaller steps

• Break each step into 3-7 smaller steps

• Keeping subdividing until each individual step is easy enough to do

• Example:▫ Learning

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Top-down Design -- Example

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Learn

Prepare

Study

Reinforce

ReadMake notesPrepare questions

Attend lectureListen and thinkComplete pracAttend tute

Record answers to questions

Revise notes

Read lecture notesRead textbook

Read exerciseDesign algorithmCode solutionTest and document

Record insights

Cara Penyajian Algoritma

• Uraian Deskriptif▫ Menggunakan bahasa yang bisa di gunakan sehari-

hari

• Menggunakan flow chart (diagram alir)

• Menggunakan pseudo-code▫ Ditulis dalam kode-kode yang disepakati yang

mempunyai arti

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Algoritma dan Flowchart

• Algoritma merupakan urutan langkah logika pemikiran detail yang diperlukan untuk memecahkan masalah.

• Algoritma dapat direpresentasikan dalam format grafis yang disebut flowchart atau diagram alir.

• Flowchart juga dapat digunakan untuk menggambarkan aliran urutan program

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Bagan-bagan Flowchart

• Terminal▫ Bentuk : rounded rectangle

▫ Mengindikasikan titik awal atau akhir

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• Connector▫ Bentuk : circle

▫ Mengindikasikan titik penghubung ke bagan lain yang terputus dalam satu halaman karena terlalu jauh atau memungkinkan memotong garis panah lain

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• Connector▫ Bentuk : pentagon

▫ Mengindikasikan titik penghubung ke bagan lain yang terputus karena beda halaman

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• Preparation atau initialization▫ Bentuk : hexagon

▫ Mengindikasikan tahap awal pemrograman (misalnya mendeklarasikan variabel, mengidentifikasikan nilai awal konstanta atau variabel)

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• Data▫ Bentuk : parallelogram

▫ Mengindikasikan masukan atau keluaran data

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• Process▫ Bentuk : rectangle

▫ Mengindikasikan proses komputasi

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• Predefined/Nested Process (Subroutine)▫ Bentuk : rectangle

▫ Mengindikasikan proses komputasi

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• Manual Operation▫ Bentuk : trapezoid

▫ Mengindikasikan operasi yang dilakukan secara manual

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• Manual Input▫ Bentuk : trapezoid

▫ Mengindikasikan masukan manual menggunakan input device (misalnya keyboard, mouse, bar code reader, imaging device)

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• Card▫ Bentuk : chamfered rectangle

▫ Mengindikasikan penggunaan card reader (misalnya punched card reader ataupun memory card reader)

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• Database atau Repository▫ Bentuk : drum

▫ Mengindikasikan penggunaan media penyimpanan basisdata

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• Display▫ Bentuk : CRT Symbol

▫ Mengindikasikan proses penampilan informasi untuk dibaca atau dilihat user di layar monitor atau projector

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• Report▫ Bentuk : Sheet

▫ Mengindikasikan proses pencetakan laporan untuk dibaca atau dilihat user menggunakan printer atau plotter

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• Annotation▫ Bentuk : Arrow

▫ Mengindikasikan hubungan presedensi antar operasi atau alur urutan operasi

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• Decision▫ Bentuk : diamond

▫ Mengindikasikan pencabangan alternatif operasi dengan pengambilan keputusan berdasarkan kriteria atau kondisi

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Decision / Condition Structure

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YES

NO

YES

NO

YES

NO

YES

NO

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Repetition / Recursive Structure

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YES

NO

YES

NO

Metodologi Pengembangan Program

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Mulai

Analisis Domain Masalah

Merumuskan Algoritma

SemuaSkenarioTertulis ?

Mapping Flowchart

StrukturLogika

Sesuai ?

Verify Program Code

Identifier,Syntax,

Semantic ?

Debug Listing Program

Compile Machine Code

CompileBerhasil

?

Eksekusi Program

EksekusiBerhasil

?

Keluaran Program Sesuai ?

Eksekusi Program

Selesai

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Contoh Algoritma

Step 1: Turn the stereo on.Step 2: If the band is set to FM, switch it to AM.Step 3: If the station is set to a station greater

than 610, turn the station to the left until 610 is reached.

Step 4: If the station is set to a station less than 610, turn the station to the right until 610 is reached.

Step 5: Listen to the best sports talk station in the country.

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Contoh Flowchart

Algoritma dan Flowchart - anggafanani.lecture.ub.ac.idanggafanani.lecture.ub.ac.id/files/2014/10/Algoritma-dan-Flowchart... · Algoritma dan Flowchart Angga Akbar Fanani 1 Problem

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