1. General Algorithms for Common Business Problems

2. Simple Program Design, Fourth Edition Chapter 10
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
Simple Program Design, Fourth Edition Chapter 10

3. Simple Program Design, Fourth Edition Chapter 10
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
Simple Program Design, Fourth Edition Chapter 10

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
Simple Program Design, Fourth Edition Chapter 10

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
Simple Program Design, Fourth Edition Chapter 10

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
Simple Program Design, Fourth Edition Chapter 10

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
Simple Program Design, Fourth Edition Chapter 10

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)
Simple Program Design, Fourth Edition Chapter 10

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_totals 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
Simple Program Design, Fourth Edition Chapter 10

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
Simple Program Design, Fourth Edition Chapter 10

11. Simple Program Design, Fourth Edition Chapter 10
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
Simple Program Design, Fourth Edition Chapter 10

12. Simple Program Design, Fourth Edition Chapter 10
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
Simple Program Design, Fourth Edition Chapter 10

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
Simple Program Design, Fourth Edition Chapter 10

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
Simple Program Design, Fourth Edition Chapter 10

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 File’1
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
Simple Program Design, Fourth Edition Chapter 10

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
Simple Program Design, Fourth Edition Chapter 10

17. Simple Program Design, Fourth Edition Chapter 10
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
Simple Program Design, Fourth Edition Chapter 10