Pseudocode Algorithms Using Sequence, Selection, and Repetition

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Pseudocode Algorithms Using Sequence, Selection,
and Repetition
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Objectives

• In this chapter you will be able to
• Develop solution algorithms to eight typical
  programming problems using sequence, selection,
  and repetition constructs

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Eight Solution Algorithms

• This chapter develops solution algorithms to
  eight programming problems of increasing
  complexity
• All the algorithms will use a combination of
  sequence, selection, and repetition constructs
• The algorithms have been designed to be
  interactive or to process sequential files

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1 Defining the Problem

• It is important that you divide the problem into
  its three components
• Input
• Output
• Processing

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2 The Control Structures Required

• Once the problem has been defined, write down the
  control structures (sequence, selection, and
  repetition) that may be needed, as well as any
  extra variables that the solution may require

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3 The Solution Algorithm

• Having defined the problem and determined the
  required control structures, devise a solution
  algorithm and represent it using pseudocode

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4 Desk Checking

• You will need to desk check each of the developed
  algorithms with two or more test cases

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Example 6.1 Process Number Pairs

• Design an algorithm that will prompt for and
  receive pairs of numbers from an operator at a
  terminal and display their sum, product, and
  average on the screen. If the calculated sum is
  over 200, an asterisk is to be displayed beside
  the sum. The program is to terminate when a pair
  of zero values is entered
• A Defining diagram (shown on page 74)

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Example 6.1 Process Number Pairs

• B Control Structures Required
• A DOWHILE loop to control the repetition
• An IF statement to determine if an asterisk is to
  be displayed
• Note the use of the NOT operator with the AND
  logical operator
• C Solution algorithm
• Refer to the code of the solution algorithm on
  page 74 of the textbook

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Example 6.2 Print Student Records

• A file of student records consists of S records
  and U records. An S record contains the
  students number, name, age, gender, address, and
  attendance pattern full-time (F/T) or part-time
  (P/T). A U record contains the number and name
  of the unit or units in which the student has
  enrolled. There may be more than one U record
  for each S record. Design a solution algorithm
  that will read the file of student records and
  print only the students number, name, and
  address on a STUDENT LIST.
• A Defining Diagram (shown on page 75 of the
  text)

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Example 6.2 Print Student Records

• B Control Structures Required
• A DOWHILE loop to control the repetition
• An IF statement to select S records
• C Solution algorithm
• Examine the pseudocode illustrated on page 75 of
  the textbook

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Example 6.3 Print Selected Students

• Design a solution algorithm that will read the
  same student file as in Example 6.2, and produce
  a report of all female students who are enrolled
  part-time. The report is to be headed PART TIME
  FEMALE STUDENTS and is to show the students
  number, name, address, and age
• A Defining Diagram (shown on page 76)

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Example 6.3 Print Selected Students

• B Control Structures Required
• A DOWHILE loop to control the repetition
• An IF statement or statements to select S,
  female, and part-time (P/T) students
• C Solution Algorithm
• Several algorithms for this problem will be
  presented, and all are equally correct
• The algorithms only differ in the way the IF
  statement is expressed, as shown in the code on
  pages 76 and in Solution 2 on page 77 of the
  textbook

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Example 6.4 Print and Total Selected Students

• Design a solution algorithm that will read the
  same student file as in Example 6.3 and produce
  the same PART TIME FEMALE STUDENTS report. In
  addition, you are to print at the end of the
  report the number of students who have been
  selected and listed, and the total number of
  students on the file
• A Defining Diagram (shown on page 78)

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Example 6.4 Print and Total Selected Students

• B Control Structures Required
• A DOWHILE loop to control the repetition
• IF statements to select S, female, and P/T
  students
• Accumulators for total_selected_students and
  total_students
• C Solution Algorithm
• Examine the code listed on page 78 of the
  textbook

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Example 6.5 Print Student Report

• Design an algorithm that will read the same
  student file as in Example 6.4 and for each
  student, print the name, number, and attendance
  pattern from the S records (student records)
  and the unit number and unit name from the U
  records (enrolled units records) as shown on page
  79 of the textbook. At the end of the report,
  print the total number of students enrolled
• A Defining Diagram (shown on page 79)

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Example 6.5 Print Student Report

• B Control Structures Required
• A DOWHILE loop to control the repetition
• An IF statement to select S or U records
• An accumulator for total_students
• C Solution Algorithm
• Examine the code illustrated on page 80 of the
  textbook for this program problem

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Example 6.6 Produce Sales Report

• Design a program that will read a file of sales
  records and produce a sales report. Each record
  in the file contains a customers number, name, a
  sales amount, and a tax code. The tax code is to
  be applied to the sales amount to determine the
  sales tax due for that sale, as shown in the
  table on page 80 of the textbook. The report is
  to print a heading SALES REPORT, and detail
  lines listing the customer number, name, sales
  amount, sales tax, and the total amount owed
• A Defining Diagram (shown on page 81)

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Example 6.6 Produce Sales Report

• B Control Structures Required
• A DOWHILE loop to control the repetition
• A case statement to calculate the sales_tax
• C Solution Algorithm
• Examine the code illustrated on page 81 which is
  the solution for this program problem

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Example 6.7 Student Test Results

• Design a solution algorithm that will read a file
  of student test results and produce a student
  test grades report. Each test record contains
  the student number, name, and test score (out of
  50). The program is to calculate for each
  student the test score as a percentage and to
  print the students number, name, test score (out
  of 50), and letter grade on the report. The
  letter grade is determined using the listing on
  page 81 of the text
• A Defining Diagram (shown on page 82)

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Example 6.7 Student Test Results

• B Control Structures Required
• A DOWHILE loop to control the repetition
• A formula to calculate the percentage
• A linear nested IF statement to calculate the
  grade. (The case construct cannot be used here,
  as CASE is not designed to cater for a range of
  values.)
• C Solution Algorithm
• Refer to the code shown on page 82 of the textbook

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Example 6.8 Gas Supply Billing

• Refer to the background of the Domestic Gas
  Supply company on page 83 of the text. Design a
  solution algorithm that will read the customer
  usage file, calculate the amount owing for gas
  usage for each customer, and print a report
  listing each customers number, name, address,
  gas usage, and the amount owing. Read the
  remainder of the problem specification on page 83
  and at the end of the report, print the total
  number of customers and the total amount owed to
  the company
• A Defining Diagram (shown on page 83)

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Example 6.8 Gas Supply Billing

• B Control Structures Required
• A DOWHILE loop to control the repetition
• An IF statement to calculate the amount_owing
• Accumulators for total_customers and
  total_amount_owing
• C Solution Algorithm
• Examine the code shown on page 84 of the
  textbook, which shows the pseudocode for this
  problem

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Summary

• This chapter developed solution algorithms to
  eight typical programming problems
• The approach to all eight problems followed the
  same pattern
• The problem was defined, using a defining diagram
• The control structures required were written
  down, along with any extra variables required
• The solution algorithm was produced, using
  pseudocode and the three basic control
  structures sequence, selection, and repetition