By Gareth Mitchell
Digital Planet, BBC World Service
Gareth gets nostalgic at Bletchley
The BBC World Service's technology radio programme, Digital Planet, goes to the National Museum of Computing at Bletchley Park to explore the history of personal computing.
Silence on the radio can be both troubling and mysterious in equal measures. After all, a lack of audio when sound is all you have, makes quite an impact.
So, one of my favourite moments in our tour of Bletchley Park is the silence, albeit a very brief one, that follows one of the questions I asked Kevin Murrell, the curator of the PC Gallery at the museum and Bill Thompson, BBC columnist and Digital Planet studio commentator.
Standing in front of an original Apple Macintosh, sharing a display with an early IBM PC, the question to them was, which of these two was the most important in the story of personal computing? Was it the Macintosh that brought us the graphical user interface that we all now take for granted on our desktops? Or was it the affordable, modular PC?
This pause for thought came just as we had revelled in personal computing nostalgia. Next to the Mac and the PC were their ancestors from the 1970s and early 80s. A real treat was an original Sinclair ZX80, the calculator-like microcomputer with that horrendously hard to type on plastic keypad.
Next to that, there was a Commodore Vic 20, my first ever computer. Its entire 3.5k of memory, is smaller than the file size of an email.
Also on display, were blasts from the past like the Acorn Atom, Dragon 32, Oric-1, Commodore PET and Apple II. There was even a fully working BBC Micro on which Bill revisited his programming past.
Struggling with a now unfamiliar and long forgotten keyboard layout, he managed '10 PRINT "BILL", 20 GOTO 10'.
Colossus could read 6,000 characters per second
Having gone back to BASIC, we reflected on the shift from computers that you programme yourself and in some cases build yourself to today's world of relatively standardised ready-to-go plastic boxes.
But just down the corridor at Bletchley Park, was a beast that made even the Sinclair ZX Spectrum look like the height of modernity.
Occupying a large room, with the whiff of hot thermionic valves and a clatter of relays from old telephone exchanges was Colossus.
This aptly named brute was the star code-cracker of the Second World War. It has been completely rebuilt and now chugs away in full working order at Bletchley.
Its job was to help intercept communications between Hitler and his most senior generals. Ciphers intercepted by radio were fed in to Colossus on reels of paper tape punched with holes.
It was Colossus' job to unravel the settings that the German operators had programmed into their cipher machines. Colossus could read 6,000 characters per second, an astonishing technical feat for the day.
Colossus was top secret - it was only fully declassified in 2002 - so it had little direct impact on the development of today's computers.
But many of those who worked on it found their way in to the post-war computer industry and no doubt brought much of their knowledge to the forerunners of the machines that now sit on our desks.
For Digital Planet producer Michelle Martin, the rhythmic mechanical workings of Colossus were a radio gift and they provide a rich aural accompaniment to the interview we recorded with Tony Sale, who led the rebuild project at Bletchley.
But the sounds of Colossus were literally music to the ears of composer Matthew Applegate AKA 'Pixelh8' who has produced a number of tracks based on samples of the mighty code cracker's teleprinter.
On Digital Planet, Matthew told us how he collaborated with Bletchley Park to bring the sounds of its many historical computers to music, through a thoroughly modern movement called 'chiptunes'.
Another of Pixelh8's chip tunes is a remix of the Digital Planet them music that he produced especially for us. It's even now available as free ring tone.
I have the ring tone on my own mobile phone. A device with orders of magnitude more processing power than Colossus. Oh, and what was the most influential early personal computer - the IBM or the Mac? Well, download the Digital Planet podcast or hear us through the iPlayer.