My First Computer

These pictures were taken in my college days. I went to school and worked at the Polytechnic Institute of Brooklyn - Microwave Research Institute. In those days there were no computers as we know them now (in 2006). The computer you see here is called the Bell Mark IV. It may well be the 4th digital computer ever built. (There was no such thing as a Personal Computer - PC). The Mark IV was built by the Bell Telephone Co. (now AT&T). There are no integrated circuits or transistors here. Not even a vacuum tube. The whole thing is made with relays.

Ones and zeros of the binary code were represented by relays. If the relay was open it was a zero. If it was closed it represented a one. Rows of relays became computer bytes. If the code was hexadecimal then eight relays would be a byte. Likewise on the punched tape storage device each row of eight holes represented one byte. The tape was fed through the "punching" (writing) and or the sensing (reading) machine. Sensing was done by phototubes that sensed the absence or presence of light.

		The fellow in the picture is a professor from India. He came as a visiting professor in electrical engineering.
The so called "Test Panel" was actually a telephone company switch panel

At the time this computer was already obsolete - so our school was willing to donate it to the University of Bihar. We suggested that new developments in computers would make this machine obsolete before it ever got to India and got re-assembled. But our professor friend said that there were no other computers in India and this would surely be the first. So we dismantled it and hauled it out of the building to be shipped all the way to Bihar.


A bank of relays - the "RAM" of the machine		The "backplane" interconnecting the banks of relays

Everything was mechanical - storage consisted of punched tape (paper tape with holes punched for bytes).		The top of a relay rack showing bus wiring up there

*That's me cutting the bus cables so we could separate the racks**		That's the professor taping up the ends of the cables

Finishing taping up the ends of the cables		Out she goes - this is one rack. The whole computer took up a medium size room however no cooling was needed since there was nothing to get hot with this machine

_______________________________________________________________________________________ * in case you are wondering how in the world these cables with hundreds of wires each could ever be put back together, we asked the professor this question. He said "we have very good telephone wiremen in India." (Every wire had a unique color code in the insulation - which was cotton). NOTE: The computer is essentially a collection of telephone switching panels rewired to do digital logic.
In the picture above and to the left you see that the computer was on the fourth floor of a building. Each rack had to be hauled out of a (removed) window by a large crane and put onto a flatbed truck. You should be aware that this machine was less powerful than the smallest microcomputer today. It also was continuous trouble because the relays would "stick." When that happened the machine would stop (we jokingly said it was "in tilt" referring to pinball machines). So you would go into the computer room and find the stuck relay. A small file was used to "clean" the contacts, then the program was "resumed."