The earliest references to computers in the school magazine appeared over sixty years ago when pioneering Old Portmuthians were reported to be forging careers in computer programming for a range of new and exciting applications. Having learnt the new skills after leaving the school, OPs were working on the 1961 census as well as in military and telecommunications development. 

 In 1964, Physics teacher Mr Starling encouraged some Lower Sixth pupils, under his guidance, to design and build a computer. The machine had electro-mechanical relays and was able to add and subtract in binary arithmetic. It took half a minute to add two numbers.  

The computer quickly fell into disuse but, five years later, some pupils discovered parts of it in a cupboard. But Mr Starling had left and no plans for it had survived, so they spent their Physics lessons, Maths lessons, and a lot of spare time developing it. Their reward was the ability to multiply and divide numbers. Progress was being made.  

Using some scrapped computer parts (which had been made in the 1940s for the Admiralty Surface Weapons Establishment on Portsdown Hill), pupils rebuilt the 1964 computer but it was found to be working twenty times faster than expected and would not reliably stop. It was rebuilt once again and transistors were introduced. But it remained erratic in its performance, achieving the correct calculation only once in every five attempts. It was decided to give up on it and build a new, completely transistorised machine. It is not known if this was successful.  

Through the 1960s, pupils visited Sussex University, where a computer with heat-generating valves occupied a large, air-conditioned room, and attended talks about how computers were going to change the world. From 1971, an annual pilgrimage to Cosham was organised for Lower (Junior) School boys to try out a computer that was in the proud possession of Highbury Technical College. Each boy was “able to process his own programme through the computer”. But it was to be some years before "information technology", as we now know it, became a part of PGS and the nation’s school’s curricula. 

In 1977 the school was offered a free Honeywell 115 Disk Computer that was surplus to a local company’s requirements. It offered “high internal speed” and “16k to 32k characters of internal memory”. The school governors declined the offer. Instead, money was raised for a computer for the Lower School - believed to have been a Commodore PET. This was soon in great demand by pupils during and after school. It was reported that "the games programmes attract the most interest, but a desire to explore the machine's practical application is already being shown, and it is hoped to be able to devise a course in the basic principles for next year's Uppers." At about the same time the Upper (Senior) School purchased four Commodore PETs, two for use in the Maths Department and one each in the Chemistry and Physics departments. A Compter Club was formed and another was added and networked to share a dot matrix printer. Memory size was doubled from 16k to 32k following the donation of extra memory chips by a parent.  

The BBC - in its valued public service role - initiated a computer literacy scheme and invested a lot of time and resources into raising awareness and promoting computing as an exciting subject and career choice and a vital investment in the country’s future. The BBC Micro, made by Acorn, became the standard in state schools. By 1983, two basement storerooms in E block were reported to have been converted into a Computer Centre with "up-to-date computer equipment"and the first school prize for computing was initiated. Commodores were still in use for learning Basic and were popular, being described as versatile and "not ready for pensioning off". A Sinclair ZX81 was added and was found, with its wedge shape, to be useful as a doorstop and BBC Micros, long overdue, arrived. A printer and a bar-code reader also were generously donated. A Tandy TRS-80 and Sinclair QLs were added, the latter proving "surprisingly reliable". At an Open Day it was used by pupils to offer computer dating.  

Mr Thornton, teacher of Maths, later wrote, "The computer centre was a hive of activity late into the night. Pupils were able to write their own programs then and were interested in the intellectual exercise of how the computer worked. Courses on machine-code programming were led by pupil experts and pupil knowledge led to them reaching the British finals of the Computer Quiz in successive years and winnings several programming prizes. Voice recognition and robotics attracted interest: a team led by pupils worked for Acorn producing a superb implementation of the COMAL language for the BBC Micro in 16k. In 1986, the first Head of Computing, Mr Harrison, was appointed, heading a department of which he was the only member. And, for the first time, computing appeared on the timetable with, initially, a double period for Middle School pupils. The digital age was about to take off at PGS.