Flowchart.ppt 653k1k

School of Business Eastern Illinois University

Program Flowchart, Pseudocode & Algorithm development Week 2: Wednesday 1/22/2003 Friday © Abdou Illia, Spring 2003

1/24/2003

Project 1 

Exercise # 8, page 57 Bohl & Rynn’s textbook

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Due date: February 3rd, 2003

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Learning Objectives 

Understand the relation between Algorithm and Pseudocode or program flowchart

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Draw flowcharts

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Write pseudocodes

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Recall form Class 2 & 3 

Use of tools by analyst/programmer in SDLC

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Design/Programming tools used for: –

Specifying problem-solving logic

Example Pseudocode: English-language statements that describe the processing steps of a program in paragraph form.

START READ EMPLOYEE DATA COMPUTE GROSS PAY COMPUTE DEDUCTIONS COMPUTE NET PAY WRITE EMPLOYEE PAYCHECK STOP

Algorithm ? 

Step-by-step procedure to solve a problem

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An algorithm can be expressed using: – – –

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A System Flowchart A Program Flowchart A Pseudocode, etc.

Any algorithm must meet the following requirements: – –

Use operations from only a given set of basic operations (+,-,/,*,<,>…) Produce solution in a finite number of such operations

Example of algorithm (program flowchart) Algorithm for determining salespersons’ pay

REGSALES = Regular sales amount

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SALESALES = Reduced sales amount REGCOM = Regular commission (6%) SALESCOM = Sales commission (3%) PAY = Total pay due

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Algorithm vocabulary SYMBOLS START

NAME

USE

Terminal interrupt symbols

Terminal point (start, stop, or break)

STOP Input/Output symbol

Process symbol

Reading data from an input medium or writing data to an output medium

Processing input data

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Algorithm vocabulary SYMBOLS

NAME

USE

Flowline symbol

Sequence of operations and direction of data flow

Decision symbol

Predefined-process symbol

Decision-making operations

Operations specified elsewhere (not in the current algorithm)

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Algorithm vocabulary SYMBOLS

NAME

USE

Connector symbol

Exit to, or entry from, another part of the Flowchart

Preparation symbol

Control operations: Set limit on loop-control variables, Initialize accumulators, etc.

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Algorithm vocabulary Item

Meaning

Variables

Data items whose values may change, or vary during processing

Data independence

Using Variables instead of their specific values gives a program the capacity to perform processing on any set of input data.

Assignment statement

Statement that assign a value (calculated or not) to a variable

Constant

A value that doesn’t change

Example READ REGSALES, SALESALES

Comment 1) Variables names are placeholders for values 2) Variable names are chosen by programmer 3) Names should be descriptive

READ $1000, $3000

REGCOM = REGSALES *.06

.06

The computer will perform the calculation first, and then, assign the result to REGCOM

IFTHENELSE / DECISION SYMBOL An Example

General form :

READ AMOUNT

:

NO

Is Condition True ?

NO

YES

Could be many processings,…

AMOUNT

DISCOUNT = AMOUNT * .10

SUBBIL= AMOUNT

SUBBIL = AMOUNT – DISCOUNT

Processing 2

: :

YES

> 200 ? Processing 1

Processing 3

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Could be many processings,…

: :

Exercise 1: Tuition bill Problem

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Write the program flowchart to prepare a tuition bill. The input will contain the student name, Social Security Number, and total number of credits for which the student has enrolled. The bill will contain the student name, Social Security Number, and computed tuition. Total credits of 10 or more indicate that the student is full-time. Full-time students pay a flat rate of $1000 for tuition. Total credits of less than 10 indicate that the student is part-time. Part-time students pay $100 per credit for tuition. Exercise 11 (Chapter 3)

(To be done in class)

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Exercise 1’s solution: (Part 1: System Flowchart)

(To be done in class)

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Exercise 1 solution: (Part 2: Program Flowchart)

Project 1

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Write a program flowchart and corresponding pseudocode to solve the following problem: Assume the input for a student is name, student number, and three grades. Output the student name and an S (Success) if the average of the three grades is 65 or more. Otherwise (else), output the student’s name, a U (Unsuccess), and the number of additional points needed for an S.

Exercise 2: Billing problem

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Exercise 11 (Chapter 2)

Look at the program flowchart on the next slide, and answer the following questions: (a)

For what variables are values read as input ?

(b)

What variables’ values are output ?

(c)

What constants are used ?

(d)

Simulate the execution of this algorithm, assuming the values shown below are read as input for the first four variables named. NAME

Mrs. A. B. Wallace

ITEM

Blouse

QTY

3

PRICE

49.99

AMTOD DISCOUNT SUBBILL TAXES BILL

Exercise 2: Billing problem Exercise 11 (Chapter 2) START READ NAME, ITEM, QTY, PRICE AMTOD = QTY * PRICE

DISCOUNT = AMTOD * .10 SUBBILL = AMTOD - DISCOUNT

TAXES = SUBBILL * .05

BILL = SUBBILL + TAXES

WRITE NAME, ITEM, BILL

STOP

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Exercise 1 solution: Program Flowchart & corresponding Pseudocode

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START READ NAME, SSN, CREDITS

NO

CREDITS

Pseudocode for Tuition problem Start YES

≥ 10 ?

Read NAME, SSN, CREDITS IF CREDITS >= 10 THEN

TUITION =

TUITION = 1000

TUITION = 1000

100 * CREDITS

ELSE TUITION = 100 * CREDITS WRITE NAME, SSN, TUITION

ENDIF Write NAME, SSN, TUITION Stop

STOP

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Pseudocode 

Other common way to represent algorithms

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Similar to programming languages like Visual Basic but –

Does not require strict rules as programming languages

Pseudocode for Tuition problem (see Slide12) Start Read NAME, SSN, CREDITS IF CREDITS >= 10 THEN UPPERCASE for variable names

TUITION = 1000 ELSE TUITION = 100 * CREDITS

UPPERCASE for Reserved words ENDIF

Write NAME, SSN, TUITION Titlecase

Lowercase for non- reserved words

Stop

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Pseudocode

Pseudocode for Tuition problem (see Slide12) Start Read NAME, SSN, CREDITS IF CREDITS >= 10 THEN Use of indentation (i.e. clauses are indented a few positions) for clarity

TUITION = 1000 ELSE TUITION = 100 * CREDITS ENDIF Write NAME, SSN, TUITION Stop

Exercise 3: Weekly Payroll problem

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Exercise 19 (Chapter 4)

Construct a program flowchart and corresponding pseudocode to solve the following problem: ABC company needs a weekly payroll report for its salespeople. Input to the program is a salesperson’s name, number, and weekly sales. Output is the salesperson’s name, number, and pay. Each salesperson receives a base pay of $300 as well as a 10% commission on his or her total sales up to and including $500. Any sales over $500 merit a 15% commission for the employee. (For example, if sales = $600, then pay = $300 + $50 [or .10 * 500] + $15 [.15 * 100] = $350). Use a DOWHILE loop and a counter to compute the weekly payroll for exactly 20 employees.

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Exercise 3’s solution: (Part 1: System Flowchart) NAME, NUM, SALES

WEEKLY PAYROLL PROGRAM

NAME, NUM, PAY

(To be done in class)

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Exercise 3 solution: (Part 2: Program Flowchart)

Exercise 3 solution: (Part 3: Pseudocode) (To be done in class)

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Algorithm Development Process 

Design verification, in order to: – –

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Prevent errors from occurring Detect and correct errors soon

Selection of Review Team for: – –

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Informal design review or Structured design review

Structured Design Review: – –

Selection of representative values of input (data normally expected, extreme values, invalid data) Following designed algorithms to determine what output are produce.

Summary Questions 1. Distinguish between Algorithm on the one hand, and Program flowchart and Pseudocode on the other hand. Discuss the relations between the two. 2. (a) List the main keywords used in Pseudocodes. (b) What control structures they represent. You should know how to design program logic using Program Flowcharts & Pseudocodes (Review Exercises 1,2,3 above & Exercise 15 Ch.4 and answer on page 339)

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