The ICT 1301 Resurrection Project.
Initial Orders Funtionality
The primary function of initial orders was to prepare the machine and then load
a working program into the machine.
To do this the operator set the manual indicators ( a group of switches on the control console ) according to what he wanted done. Then started the process by pressing the INITIAL ORDERS Button, placing the run stop switch to RUN and pressing the start button.
The Initial Orders program was loaded from the DRUM, as the program ran it examined the switches and decided what actions had to be taken, for example:-
Recovering the Code
To complete this project we needed to recover the initial orders from this machine, the drum
was not functional at all. Although we had a few listings we were unsure if any listing was
the 'Correct' listing for this machine. As soon as the drum started to work we put
a sub project into place to recover the Initial Orders.
This involved extracting all the 4,800 digits ( 400 words ) and comparing the results to what we knew was required, then as we improved the recovery of the drum code we could allow for gained and lost bits in the digits.
We extracted about 4 differing versions at various stages of drum repair ( a total of 19,200 digits ) the result is that we are now confident that we have a good working copy of the Code.
Without a working output device, and no code in the machine to drive a device. During this period we captured the snapshots by transmission of the code as an RS232 stream sent by hand coded software we manually keyed in each time. It was still quicker than trying to write all of those digits without error, by hand.
Needeless to say we were very pleased with this, and had a little well deserved celebration !
A Salute to Bill Foote
Initial Orders ( a Foote-Note ) excuse the Pun !
We have been contacted by Bill Foote who worked on refining the original Initial Orders code, as it went through the final stages of adaption to the original ICT 1301 Computer.
Initial Orders was stored on the reserved bands of the drum and was locked out to write orders, so that it became Read Only. In modern computer parlance, this was the Bootstrap program, it was used to load card programmes, in a relative address format, to clear and prepare drum store, issue a form feed to the line printer to set it at top of form.
In diagnosotic mode it would read binary or machine code engineering programs into the memory and even at a pinch if the card reader was being repaired, would load engineering cards into the machine via the check read brushes of the card punch, a somewhat toturous route but essential is you wished to repair the card reader and run tests on it.
The code was limited according to the size and number of drums on the machine. A half drum machine was limited to what the code could do. A full drum allowed the full set of facilities. A multi drum machine in the later end of the life of the equipment used the second set of reserved bands to extend on the facilities even further, as the example which follows shows.
As the 1301 suppoprted a full set of both decimal and sterling arithmetic functions, problems arose when the currency was changed in the UK, the potential was that all of the software written had to be recomplied, or even re-written from scratch, if the documentation for the original program had been " Mislaid ".
To aid the transition the machines were modifed to follow the conversion of any sterling functions to be decoded as decimal functions, this took the form of a keyswitch hidden under the covers. But what was the switch set to ? as lots of computing hours and even days were lost running ledger updates when the machine was switched to the wrong mode, eventually a very small extension to I/O's was added to add zero to a digit with a packed ten ( that's an Hexadecimal h0A ) in the pence position and if it came out of the mill as a two digit answer the machine was in decimal mode and if it remained packed in one digit the machine was in sterling mode.
On the 1302 ( that very rare and recently rediscovered animal ) the I/O's also allowed the starting of the Executive code, a three thousand 1301 word chunk of code that ran multiple programs and handled device transfers in a true time sharing mode. So in Summary the Initial Orders code was the loading and start point of most applications the machine ran, we have managed to recover the code from flossies drum and can now move the project forward knowing that at least the machine can be exercised and run its test software.
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