[Klug-general] Fwd: Re: Fwd: Re: Now here's a funny thing.

[Mike Evans]

Erm, yes I do remember punched cards.  My first ALGOL programs were 
written on them.

Oh and FF was never carriage return:  00 was alwas NUL and FF was always 
a deletion - DEL.  The equivalent was also true of five-bit encoding. 
These come from punched tape, originally from telex machines, and both 
codes meant 'ignore me'.  This meant that blank tape (feed holes only) 
was 00 by default and could be skipped and any section of tape could be 
deleted by punching out all the holes, creating FF's.  In this way paper 
tape could be edited rather than having to scrap it and start again.

Interestingly in later years the technique was re-used in EPROMs - at 
least by Psion.  Erasing an EPROM with UV light set all the bits to 0. 
Any bit could then be programmed to a 1 using a raised voltage one one 
of the pins and a series of write cycles to the appropriate address. 
After programming it was therefore possible to overwrite sections with 
FF and these were taken as deleted data.  No doubt the idea will get 
recycled again shortly in some other guise.