“Whoever designs a computer system must have a good understanding of the natures and skills of those people who will use it and then design the ways of working which will match their abilities and circumstances
By John Poulter, IT expert and professional member of BCS, The Chartered Institute for IT. June 2026.
The example of developing a computer system I am going to give here goes back to the earlier days of computing in the 1980s, but the lesson to be learned from it applies just as much today.
Mainframe Computers
Before personal computers (PCs) came into use, computer processing was carried out on what were known as mainframe computers. These were big things. With their associated printers, card readers and disc drives, they often occupied an entire room. At the time, even big organisations often had only one such computer, and this computer would carry out all of the processing, not only for the head office of the company but also for all of its subsidiaries too.
What each subsidiary company would do to use the central computer would be to write out on paper forms the data which it wished to be processed. These forms would then be sent as a batch to the computer centre in the head office. There the data on the forms would be keyed into punched cards which would then join a queue of jobs waiting to be fed into the computer. The computer could only process one job at a time, so it might take quite some while before the job was run. When, eventually, the job was run, the results from the computer processing would be printed out onto sheets of paper, and these sheets would then be sent back to the relevant department or subsidiary company which had submitted the data.
Setting up a computer accounting system
In this particular example, one of the subsidiary companies wished to have their accounts processed by computer. The head office therefore sent one of their computer experts to set up a computer accounting system for the subsidiary. The expert decided that the best form of accounting system for this subsidiary company should be an open-item system. This is an accounting system in which every entry to the system – including all alterations and corrections – are recorded on the computer printouts, so that all entries into the accounts would be visible without any doubts.
The computer at the head office was heavily loaded with jobs and the manager of the computer centre could only offer a weekly turn-around. That is because the whole process, from receiving the input forms, to queueing to get them punched, to queuing the job to run on the computer programme and then running it, to getting the printouts back to the subsidiary company’s accounts department, took a lot of time. As it happens, this quite suited the subsidiary company’s accounts department because it tended to run on a weekly cycle too. So, the computer expert set up an arrangement such that the clerks on the subsidiary company’s accounts department would always work with the latest printouts received from the computer centre and to use them to enter all new debits and credits for that week and also any corrections and alterations that might be necessary. This data was then all to be sent on the appropriate forms to the computer centre for processing the next week.
Finding problems with the computer system
In setting up the new computer system to work this way, the expert thought he’d been quite clever in spotting the synergy between what the computer centre could do and how the subsidiary company’s accounts department tended to work. However, as things turned out, he had indeed been quite clever, but, unfortunately, not quite clever enough.
At first the running of the new computer system went well, and after staying around for a few days in order to be sure, the expert returned to his head office thinking the job had been well done. A few weeks later he was summoned to his director’s office and was told that the new accounting system for the subsidiary company had gone haywire. The director wasn’t sure what the problem was but his instructions to the expert were simple: jump on a train and get there as fast as you can and fix it quick!
Realising and solving the problem
When the expert got there it did not take him long to find out what had gone wrong. One of the computer’s disc drives had failed, and although a replacement had been ordered it was awaiting customs clearance in the docks and could not be released. This meant that the computer in the computer centre could only process half of its workload, and so the manager of the computer centre directed that the subsidiary company’s new accounting system would only be run fortnightly instead of weekly.
Meanwhile, in the subsidiary company’s accounts department, the significance of this change was not appreciated. The clerks there were continuing to use the latest printouts which they had and were dutifully entering onto the forms the week’s new records and also any alterations and corrections which appeared to be required on the printouts. Unfortunately, since the latest printouts which they had were two weeks old the clerks were simply repeating some of the entries which they had made the previous week. Naturally, therefore, all the error correction records which were entering the system were being duplicated and then quadrupled and so on until the printouts soon became chaotic. Once the expert had recognised the problem, he was able to issue new operating instructions for the clerks in the subsidiary company’s office and the chaos was rapidly rectified.
It might seem strange that the managers and some of the clerks in the subsidiary company’s accounts department had not realised that they were simply duplicating any errors or corrections which they had entered only the week before. However, they didn’t. They just carried on doing what they’d been told to do. In parallel, the computer centre manager hadn’t appreciated the significance of the weekly cycle to the working of the new accounting system. So he hadn’t thought to tell the computer expert about the changed working cycle either.
What had the expert done wrong? Basically, he hadn’t thought to explain the critical nature of his weekly working arrangement to the computer centre manager or to the managers of the subsidiary company’s accounts department. It was actually a crucial component of the satisfactory working of the new accounting system. As a result, nobody had thought to notify him of the change of the processing cycle from weekly to fortnightly. If he had been notified, even at head office, he would have been able to devise and issue new working arrangements for the clerks in the subsidiary company’s office.
Setting up a system when things go wrong
What this illustrates is that there is more – often much more – to a computer system than just a computer programme. The new accounting computer programme itself was fine all the way through the problem and didn’t need any fixing. It was the operating arrangements which, although neat at the outset, had proved fallible to an unexpected development. Really, the expert should have known better to allow for unexpected developments to occur and to have arranged for him to be at least notified when and if they did.
Understanding the computer system users
To make the point more generally, when someone is designing a computer system, they must take account of the kind of people who will have to use it, and of the circumstances in which they would have to do so. Some people will quite naturally be technically proficient, while others will soon get hopelessly lost and confused by, say, an error message which they don’t understand. In addition, circumstances could change over time, such that some elements of the computer system might need to be modified to suit. Therefore, whoever designs a computer system must have a good understanding of the natures and skills of those people who will use it and then design the ways of working which will match their abilities and circumstances. Thus, designing and creating a computer system is much more than just specifying what a computer programme should do.
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Read more about John and his career in Archives of IT’s interview with him from 2022.
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