The USSC90, punch-cards and codes.

Our punch-station.

The 90 column punch-cards. 

A 90 column punch-card contained two rows of data, an upper half and a lower half with each 45 columns of 6 bits. 
In the punchcard, each high-bit (1) was represented by a round hole. 
The cards were stored in a controlled climate. When they got too dry, they got stiff and could brake easily and 
when they got moist they would get soft and swelled and could not be fed into the reader properly.
All data-entry was done by punching cards with a stand-alone punch-card-machine with a QWERTY-keyboard.  

Data typist

Data entry room
With these machines, alpha-numeric data was punched into the cards in the Remington-Rand code (RR), using 52 combinations of 6 bits to code numbers, characters and symbols. There were five types of punch-cards:
1- Data : with 90 characters of data punched in 6 bit Remington Rand-code (RR).
2- Programs: containing one address and one instruction in RR-code.
3- Programs in MC: with 8 instructions or numbers in the four bit code.
4- Standard routines: provided by Univac, like arithmetic- and card reading-routines.
5- The routine LOAD: to load programs. A self-loading program, started by typing in a bootstrap.

Card with RR-code

Card with MC-code

Machine code.

All instructions and operands existed of a signed word of ten digits, each digit coded biquinary. The name Biquinary did mean that each digit was coded binary, only the fourth bit represented the value 5. This value-5-code made the (hardware) calculation to access the magnetic-drum-memory more simple. Apart from the numbers there were six odd codes, named: k y t K Y T. These were used to address the three registers or were used in calculations as sentinels.

The Remington Rand card-code:

For Alpha-numeric data-entry the 90 column cards were punched in the Remington Rand code (RR), a 6 bit alfa\num.-code. This code was also used for punching programinstructions. Of this six-bit code only 51 bit-combination were meaningful since the denser bit-combinations were not used to prevent lines of holes in the punched cards, wich would make the card easy to fold and to got jammed in the high speed cardreader.
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