General Algorithms for Common Business Problems

1
General Algorithms for Common Business Problems
2
Objectives

• In this chapter you will be able to
• Provide general pseudocode algorithms to four
  common business applications. Topics covered
  are
• Report generation with page break
• Single-level control break
• Multiple-level control break
• Sequential file update

3
Program Structure

• The aim of this chapter is to present a number of
  general pseudocode solutions for typical
  programming problems
• This basic solution algorithm forms the framework
  for most commercial business programs
• It does not include processing for page headings,
  control breaks, total lines, or special
  calculations
• Examine the hierarchy chart and pseudocode shown
  on pages 161 and 162 of the textbook

4
Report Generation with Page Break

• Most reports require page heading lines, column
  heading lines, detail lines, and total lines
• Reports are also required to skip to a new page
  after a predetermined number of detail lines have
  been printed
• Examine the typical report on page 162 of the
  textbook along with the hierarchy chart and
  pseudocode of the solution algorithm on pages 162
  through 164 of the textbook

5
Single-Level Control Break

• A control break total line is a summary line for
  a group of records that contain the same record
  key
• There are two things you must consider when
  designing a control break program
• The file to be processed must have been sorted
  into control field sequence
• Each time a record is read from the input file,
  the control field on the current record must be
  compared with the control field on the previous
  record

6
Single-Level Control Break

• A Hierarchy Chart (shown on page 165)
• All control break report programs will require
  the following variables
• A variable named this_control_field which will
  hold the control field of the record just read
• A variable named prev_control_field which will
  hold the control field of the previous record
• One or more variables to accumulate the control
  break totals
• One or more variables to accumulate the report
  totals

7
Single-Level Control Break

• B Solution Algorithm (shown on page 166 and
  167)
• There are four points in this mainline algorithm
  that are essential for a control break program to
  function correctly
• Each time a new record is read from the file, the
  new control field is assigned to the variable
  this_control_field
• When the first record is read, the new control
  field is assigned to both the variables
  this_control_field and prev_control_field
• The variable prev_control_field is updated as
  soon as a change in the control field is detected
• After the end of the file has been detected, the
  module Print_control_total_line will print the
  control break totals for the last record or set
  of records

8
Multiple-Level Control Break

• Often reports are required to produce
  multiple-level control break totals
• The concepts that applied to a single-level
  control break program also apply to a
  multiple-level control break program
• The general solution algorithm that was developed
  for a single-level control break program can be
  extended by the addition of two new modules to
  incorporate a two-level control break
• A Hierarchy Chart (shown on page 169)

9
Multiple-Level Control Break

• B Solution Algorithm (shown on pages 170
  through 172)
• The points to be noted in this mainline are
• Each time a new record is read from the input
  file, the new control fields are assigned to the
  variables this_minor_control_field and
  this_major_control_field
• When the first record is read, the new control
  fields are assigned to both the current and
  previous control field variables
• After the end of the input file has been
  detected, the two modules Print_minor_control_tota
  ls and Print_major_control_totals will print
  control totals for the last minor control field
  record, or set of records, and the last major
  control field or set of records

10
Sequential File Update

• Sequential file updating involves updating a
  master file by applying update transactions on a
  transaction file
• Both files are sequential
• A new master file that incorporates the update
  transaction is produced
• A system flowchart of a sequential update program
  is illustrated on page 173 of the textbook

11
System Concepts

• Master File
• A master file is a file that contains permanent
  and semi-permanent information about the data
  entities it contains
• Transaction File
• A transaction file contains all the data and
  activities that are included on the master file
• If the transaction file has been designed
  specifically to update a master file, there are
  usually three types of update transactions on
  this file

12
System Concepts

• These are transactions to
• Add a new record
• Update or change an existing record
• Delete an existing record
• Audit Report
• An audit report is a detailed list of all the
  transactions that were applied to the master file
• Error Report
• An error report is a detailed list of errors that
  occurred during the processing of the update

13
Sequential Update Logic

• Processing involves reading a record from each of
  the input files and comparing the keys of the two
  records
• As a result of this comparison, processing falls
  generally into three categories
• If the key on the transaction record is less than
  the key on the old master record, the transaction
  is probably an add transaction
• If the key on the transaction record is equal to
  the key on the old master record, the transaction
  is probably an update or delete transaction
• If the key on the transaction record is greater
  than the key on the old master record, there is
  no matching transaction for that master record

14
Sequential Update Logic

• Sequential update programs also need to include
  logic that will handle multiple transaction
  records for the same master record, and the
  possibility of transaction records that are in
  error
• The types of transaction record errors that can
  occur are
• An attempt to add a new master record when a
  record with that key already exists on the master
  file
• An attempt to update a master record when there
  is no record with that key on the master file
• An attempt to delete a master record when there
  is no record with that key on the master file
• An attempt to delete a master record when the
  current balance is not equal to zero

15
Balance Line Algorithm

• A good general solution algorithm written in
  pseudocode was presented by Barry Dwyer in a
  paper entitled One More Time How to Update a
  Master File1
• This algorithm has been referred to as the
  balance line algorithm
• It handles multiple transaction records for the
  one master record, as well as the possibility of
  transaction record errors
• 1 Barry Dwyer, One More Time- How to Update a
  Master File, Comm. ACM, Vol. 124, No. 1, January
  1981.

16
Balance Line Algorithm

• A modularized version of the balance line
  algorithm is presented in this chapter
• A Hierarchy Chart (shown on page 176)
• B Solution Algorithm
• Refer to the mainline and subordinate modules
  shown on pages 176 through 179 of the textbook

17
Summary

• The aim of this chapter was to develop general
  pseudocode algorithms to four common business
  applications
• The applications covered were
• Report generation with page break
• Single-level control break
• Multiple-level control break
• Sequential file update