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Pan Books Ltd
Michael Bews
ZX Spectrum 48K

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Mike Wright
Chris Bourne


CPA Software helps make business decisions.

THE MAJORITY of business programs for the ZX-81 and Spectrum are based on the traditional areas of word processing, databases, spreadsheets and finance - payroll and ledger - packages. In a different area entirely the Hilderbay Critical Path Analysis program is more concerned with project planning.

CPA is a method of determining those activities in a project where a delay in the activity will cause a delay in the whole project. It can be applied to all projects where activities are started and stopped independently and which, in some cases, must be performed in a particular order. CPA has been used successfully in many fields. They include planning production, scheduling maintainence, town planning and construction. It can also be used for everyday tasks such as planning a shopping expedition or decorating, although its use in such areas is usually restricted to exercises for those being taught the methodology.

The program is designed for use by those who already have a background in CPA. That is made obvious by an impressive-looking manual which occupies two sides of A4 paper, with one of them devoted to background. Before the program can be run the usual network diagram shows the numbered activities and their duration, and cost if desired. The start and end points of the activities are also numbered independently.

Once the program has been loaded using LOAD "CPA", it asks whether a printout is required. Having entered either Y(es) or N(o) the master menu is displayed. That reminds the user of the elements of the network, gives instructions on how to get a warm re-start - i.e., without losing the data already entered - and the five options. They are SAVE problem on tape; LOAD problem from tape; enter a NEW problem; MODIFY existing data; SOLVE existing problem.

Initially the second option will be selected to enter a new problem. The program prompts for the number of activities in the network and also warns that existing data will be deleted. If that has been chosen by mistake, entering 0 returns directly to the master menu, keeping the old data.

After that the program continues to prompt for the start node, end node, duration and cost for each activity in turn. Once the data for an activity has been entered it is displayed with the activity number and the user is asked to confirm that it is correct.

Pressing any key except Y starts the data entry for that activity again. Once the data for the last activity has been entered the information for all activities is displayed. Pressing any key causes the calculation of the problem. When completed, the display shows the nodes of the activity, the earliest start time for the activity, the latest ending time, the float or amount of time an activity can be delayed without delaying the protect and the cost.

Also shown is a critical path through the network and the cost of that path. Although the critical path is displayed on-screen, for some reason it is omitted from the printout; duration and cost remain.

The program is easy to use but gives very little protection against typing errors. The manual we received with the program makes a passing reference to an example. It seems to bear little relation to the figures in the manual. The program restricts the number of nodes to being fewer than the number of activities, which is not mentioned anywhere in the documentation but can be avoided by creating dummy activities with no duration.

Improvements could be made by printing all critical paths through a network and also by giving the user the option to add activities once a problem has been set up. CPA will analyse large networks reasonably satisfactorily provided the user is prepared to tolerate its limitations. For those who wish to use a more complete package, if Hilderbay also produces the Project Planning Package at £120 plus VAT.

Critical Path Analysis is available from Hilderbay Ltd at 8-10 Parkway, Regents Park, London NW1 7AA and costs £15 inclusive of VAT.

Not Rated