IT (and Sex) were invented quite recently (allegedly)

The Chilton ICL 1906A in 1971, photograph courtesy Atlas Computer Laboratory, Chilton

Isn't it funny (and annoying) how 'the young' think they invented everything? Speaking to a lad in the pub recently he expressed his surprise "You've got a blog?" Almost a "you know how to use a computer?" (With a look of total incredulity all over his pizza-like chops.) If they ever thought about anything (other than their image) they's know that some of us were not only operating and programming wharehouse-sized mainframe beasts in the '60's, some of us were even designing them. All this even before their parents were born.

I worked on the ICL 1900 series machines for several years as an operator, programmer, shift leader and ops manager. I used George 1, 2 and 3 plus COBOL, ALGOL, FORTRAN and PLAN.

The ICL 1900 was a word machine with 24-bit words, containing 4 * 6-bit characters. Instructions were whole words, and a word could be addressed in both 'word' or 'character mode depending on the type of data it held.

Most 1900 machines were multi-programming under the control of the EXECutive or Operating System, (which, sometimes, wouldn't load from card or tape and had to be 'hand-switched' in the back of the CPU - a memory feat which hasn't been seen since.)

There were no fixed "partitions" within which programs had to abide, but there was full hardware protection to prevent one program from errantly trespassing in another's space.

Likewise all peripherals were available in a general pool and allocated to a program when requested and then released back to the pool when finished with (using a teletype as in the picture above). Every program started at address zero wherever it was located in physical memory, hardware 'datum' and 'limit' registers provided the translation/protection for user programs, which could be moved in memory as other programs altered their size or were deleted.

The memory size (core store or later ECL electronic) was typically 32K, 48K for smaller machines, 64K, 128K, 192K or 256K for larger machines.

An optional Hardware Floating Point unit was available, but tended not to be fitted on commercial machines.

The ICT (later ICL) 1900 series (I worked on earlier machines such as:- Atlas, Pegasus, 1301 and even Holleriths) was begat of a Canadian machine called the FP6000 (FP = Ferranti Packard). The main difference was the incorporation of a "standard" physical interface (i.e. a standard kind of plug) for all peripherals, and the use of a single operation code to drive all peripherals rather than having separate instructions to read a card, or print a line or whatever. The "PERI" instruction, an EXTRACODE implemented by the EXECutive, instead pointed to a small group of control words in memory which supplied the details for whatever I/O operation. This instruction caused an interupt/exchange of control to the memory-resident monitor that contained the actual low-level driver code for each type of peripheral. (The FP6000 on the other hand had "hardwired" and distinct op codes for each kind of I/O operation and did not have the concept of a resident monitor through which I/O was mediated).

Believe me, PC's are a piece of **** compared to these brutes. We may have scrunched up a few tapes and wrecked a few discs but we rarely lost any information (and what we did we could recover by the Grandfather, Father and Son system of storage.)

Speaking of screwing things up (I think I was) for the uninitiated, this is a punched card (mainly 80 column but some 40c existed). We have all probably heard of making a mistake, punching the wrong sequence of holes and then filling them up with 'chads' to save repunching it all. Well, I can admit to dropping a box full of these (over 5,000) whilst loading them into the reader and yes - it did take me all night (unpaid) to put them back in order. Those were the days - NOT.