permacomputing

commit d8f373bc788edc21171fad42ad0d3499393ce19a
parent 1511fff427ae166231cd5c22026a4d1a786c4356
Author: neau <neau@web>
Date:   Wed, 22 Jun 2022 16:45:10 +0200

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CARDIAC.mdwn
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+CARDIAC (CARDboard Illustrative Aid to Computation) is a learning aid developed by David Hagelbarger and Saul Fingerman for Bell Telephone Laboratories in 1968 to teach high school students how computers work. 
+
+The kit consists of an instruction manual and a [[paper computer]].
+
+The computer operates in base 10 and has 100 memory cells which can hold signed numbers from 0 to ±999. It has an instruction set of 10 instructions which allows CARDIAC to add, subtract, test, shift, input, output and jump. 
+
+   INP 	Input 	take a number from the input card and put it in a specified memory cell.
+   CLA 	Clear and add 	clear the accumulator and add the contents of a memory cell to the accumulator.
+   ADD 	Add 	add the contents of a memory cell to the accumulator.
+   TAC 	Test accumulator contents 	performs a sign test on the contents of the accumulator; if minus, jump to a specified memory cell.
+   SFT 	Shift 	shifts the accumulator x places left, then y places right, where x is the upper address digit and y is the lower.
+   OUT 	Output 	take a number from the specified memory cell and write it on the output card.
+   STO 	Store 	copy the contents of the accumulator into a specified memory cell.
+   SUB 	Subtract 	subtract the contents of a specified memory cell from the accumulator.
+   JMP 	Jump 	jump to a specified memory cell. The current cell number is written in cell 99. This allows for one level of subroutines by having the return be the instruction at cell 99 (which had '8' hardcoded as the first digit.
+   HRS 	Halt and reset 	move bug to the specified cell, then stop program execution.