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Encyclopedia > CARDboard Illustrative Aid to Computation

Cardiac (CARDboard Illustrative Aid to Computation) was 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 consisted of an instruction manual and a die-cut cardboard "computer". Bell Laboratories (also known as Bell Labs and formerly known as AT&T Bell Laboratories and Bell Telephone Laboratories) was the main research and development arm of the United States Bell System. ... The tower of a personal computer. ...

The computer "operated" by means of pencil and sliding cards. Any arithmetic was done in the head of the person operating the computer. The computer operated in base 10 and had 100 memory cells which could hold signed numbers from ±0 to ±999. It had an instruction set of 10 instructions which allowed CARDIAC to add, subtract, test, shift, input, output and jump.



The “CPU” of the computer consisted of 4 slides that moved various numbers and arrows to have the flow of the real CPU (the user's brain) move the right way. The had one flag (+/-), affected by the result in the accumulator. Die of an Intel 80486DX2 microprocessor (actual size: 12×6. ... In animals the brain, or encephalon (Greek for in the head), is the control center of the central nervous system, responsible for thought. ...

Memory consisted of the other half of the cardboard cutout. There were 100 cells, 98 of which were “RAM”, one was “ROM” and one which could best be described as “EEPROM”. Memory cells held signed decimal numbers from ±0 to ±999 and were written with a pencil. Cells were erased with an eraser. A “bug” was provided to act as a program counter, and was placed in a hole beside the current memory cell. The terms storage (U.K.) or memory (U.S.) refer to the parts of a digital computer that retain physical state (data) for some interval of time, possibly even after electrical power to the computer is turned off. ... Look up RAM, Ram, ram in Wiktionary, the free dictionary. ... Read-only memory (usually known by its acronym, ROM) is a class of storage media used in computers and other electronic devices. ... An EEPROM (also called an E2PROM)[] or Electronically Erasable Programmable Read-Only Memory, is a non-volatile storage chip used in computers and other devices to store small amounts of volatile (configuration) data. ... The decimal (base ten or occasionally denary) numeral system has ten as its base. ...


CARDIAC had a 10 instruction machine language. An instruction consisted of three decimal digits (the sign is ignored). The first digit was the op code (O), the second and third digits was an address (A). Addressing was one of accumulator to memory absolute, absolute memory to accumulator, input to absolute memory and absolute memory to output. A system of codes directly understandable by a computers CPU is termed this CPUs native or machine language. ...


High level languages were never developed for CARDIAC, since they would defeat one of the purposes of the device, to teach a little assembly language programming.

Programs were hand assembled, then written, by pencil into the appropriate memory cells.

Instruction Set

Opcode Mnemonic Description
0 INP Input – take a number from the input card and put it in a specified memory cell.
1 CLA Clear and add – clear the accumulator and add the contents of a memory cell to the accumulator.
2 ADD Add - add the contents of a memory cell to the accumulator.
3 TAC Test accumulator contents – performs a sign test on the contents of the accumulator.
4 SFT Shift – shifts the accumulator x places left, then y places right, where x is the upper address digit and y is the lower.
5 OUT Output – take a number from the specified memory cell and write it on the output card.
6 STO Store – copy the contents of the accumulator into a specified memory cell.
7 SUB Subtract – subtract the contents of a specified memory cell from the accumulator.
8 JMP Jump - jump to a specified memory cell. The current cell number is written in cell 99. This allows for one level of subroutines.
9 HRS Halt and reset – move bug to the specified cell, then stop program execution.


Programs were run by first sliding three slides so that the number in the instruction register equaled the number in the memory cell the bug was sitting in. Once that was done the bug was moved to the next memory cell. The user then followed an arrow which would then tell them what to do next. This would continue for all of program execution.


There are two ways to get one of these devices. One is from Comspace Corporation at [1]. Another is a recreation based off of pictures from the internet from [2].



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