COP 1002

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COP 1002

• Chapter 6
• By Ali Fazelpour

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Review of DOWHILE

• Counter Controlled Loop
• Header Record Logic
• Similarity
• Test at the beginning of Loop
• Both based on counter
• Steps to be repeated in the TRUE Path
• Number of times to repeat is known in advance
• Difference
• First input record (the header record) specifies
  the no. of times to execute the loop

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DOWHILE Issue

• What if we do not know the number of times to be
  repeated in advance
• E.g., No. of Customers to do shopping today
• No. of defective parts to be received today
• Lets modify the structure to accommodate the new
  situation

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Trailer Record Logic (TRL)

• Trailer Record Logic Trailer Record (Last Input
  Record) to control the loop
• This record is a signal to the computer that no
  more data to process
• Trailer record contains some data that differs
  from the rest of the input.

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Trailer Record Logic (TRL)

• This data will be used in the loop test to
  determine when all input has been processed.
• What type of Information in the Trailer Record
  It depends on the Algorithm
• It differs from algorithm to algorithm
• E.g., Student File Name, SSN, and so on
• SSN 000-00-000 is a good trailer data
• Dummy data Trailer data

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Problem 6.1 Defective Parts

• Problem Description
• A manufacture produces a large number of parts in
  two plants
• Some parts are defective and will be returned to
  the headquarter
• Input Plant code, Part , Part type and returned
  date
• Plant Code is 1,2

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Problem 6.1

• A program that reads data and prints the
  following output
• Total number of defective parts for each plant
• Trailer Record Plant Code 9
• Fig. 6.1 ( page 102)
• Fig. 6.2 (Page 103)

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Problem 6.1

• Psuedocode Fig 6.3 (Page 104)
• Heading Lines
• Detail Lines
• Total Lines
• Priming Read and Loop Read

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Problem 6.2 Defective Parts Using Modules

• Problem description
• The same as problem 6.1
• Modular Approach
• Structure Chart Fig. 6.4 (Page 107)
• Flowchart Fig. 6.5 (Page 107) Main Module

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Problem 6.2 Defective Parts Using Modules

• Flowchart Pseudocode Fig. 6.7 (Page 108)
  Process Heading Module
• Flowchart Pseudocode Fig. 6.8 (Page 108)
  Process Initialization Module
• Flowchart Pseudocode Fig. 6.9 (Page 108)
  Process Totals Module
• Flowchart Fig. 6.10 (Page 109) Process Detail
  Record Module
• Pseudocode Fig. 6.11 (Page 109) Process Detail
  Record Module

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Automatic End-of-File processing

• Not necessary to have a trailer record
• because most programming languages have a
  build-in function to recognize the end of file
• Instead of checking for a trailer value, check
  for EOF
• Flowchart Fig 6.12/ EOF Priming/Loop Read (Page
  110)
• Pseudocode (Fig. 6.13 Page 111)
• Tests are changed
• Rather than testing for a specific value as
  trailer record, we replace it with EOF Test

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Problem 6.3 Defective Parts with Multiple
headings

• Output heading on every page of the report, not
  just the first page
• Number each page
• Use EOF Processing approach

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Problem 6.3

• SOLUTION
• Output the headings at the top of every page
• Counter (LINECNT) to keep track of the number of
  detail lines that printed on each page
• LINECNT 0 each time a detail line printed
  increase the LINECNT by 1
• LINECNT gt 55 Start new page and print the
  headings
• PAGECNT to keep track of page number
• PAGECNT 1, increment by 1 every time we have a
  new page

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Problem 6.3

• STRUCTURE CHART Fig. 6.14 (Page 112)
• PROCESS HEADING module is not controlled by mail
  module any more
• It is controlled by PROCESS A DETAIL RECORD
  Module
• Because we need to check if we have enough room
  to print detail record in the current page,
  otherwise go to next page
• Checking for LINECNT gt 55

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Problem 6.3

• Flowchart for Main Module Fig. 6.15 (Page 113)
• No call to PROCESS HEADING MODULE, because it is
  not controlled by main module any more

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Problem 6.3

• Pseudocode for Main module (Fig. 6.16/Page 113)
• Start/Stop
• Priming READ/Loop Read

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Problem 6.3

• Flowchart Pseudocode Fig. 6.17 (Page 114)
  Process Initialization Module
• Flowchart Pseudocode Fig. 6.18 (Page 114)
  Process Totals Module
• Flowchart Fig. 6.19 (Page 115) Process Detail
  Module
• Pseudocode Fig. 6.20 (Page 115) Process Detail
  Module
• Flowchart Pseudocode Fig. 6.21 (Page 116)
  Process Heading Module

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Multiple Headings Summary

• Two additional counters
• Initialization/Increment-Decrement/Testing
• LINECNT of lines being printed on each page
• PAGECNT of pages being printed

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Multiple Heading Summary

• Flowchart Fig. 6.22 (Page 117) Multiple
  Heading Summary
• B000 Process Initialization Module
• MAXLINES 55 Named Constant Its value does
  NOT change during program execution
• Refer to MAXLINES instead of a constant such as
  55
• Advantage of Named Constant Flexibility
• B010 process a detail Record Module
• Refer to MAXLINES instead of 55
• C000 Process Heading Module

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Problem 6.4

• Problem description
• Input Names, Address, Credits
• Print Names/credit for more than 60 credits,
  otherwise do nothing (NULL ELSE)
• Trailer Record Negative credit
• Headings on each page and page number

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Problem 6.4

• Structure Chart
• Fig 6.23 (Page 118)
• Flowchart Fig 6.24 (Page 119) - Main Module
• Pseudocode Fig 6.25 (Page 119) Main Module

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Problem 6.4

• Flowchart Fig 6.26 (Page 120) Detail Record
  Module
• Pseudocode Fig 6.27 (Page 121) Detail Record
  Module
• Flowchart Pseudocode Fig 6.28 (Page 121)
  Process Initialization Module
• Flowchart Pseudocode Fig 6.29 (Page 121)
  Process Heading Module

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DOWHILE Summary