IBM 305 RAMAC
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The IBM 305 RAMAC was the first commercial computer that used a moving-head hard disk drive for secondary storage. The system was publicly announced on September 14, 1956, with test units already installed at the U.S. Navy and at private corporations. RAMAC stood for "Random Access Method of Accounting and Control", as its design was motivated by the need for real-time accounting in business.
IBM 305 RAMAC system: IBM 305 main system (Processing unit, magnetic process drum, magnetic core register, electronic logical and arithmetic circuits) IBM 370 printer (left), IBM 380 console (right)
One RAMAC storage disk showing head crash damage
IBM 305 at U.S. Army Red River Arsenal. Foreground: two 350 disk drives. Background: 380 console and 305 processing unit
RAMAC mechanism at Computer History Museum
Plugboard
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A plugboard or control panel is an array of jacks or sockets into which patch cords can be inserted to complete an electrical circuit. Control panels are sometimes used to direct the operation of unit record equipment, cipher machines, and early computers. The array of holes is often contained in a flat removable panel that can be inserted into a machine and pressed against an array of contacts. This allows the machine to be quickly switched between different applications.
IBM 402 accounting machine control panel wiring. This board was labeled "profit & loss summary."
Reverse side of the same 402 plugboard, showing the pins that make contact with the machine's internal wiring. The holes were called hubs.
An operator inserting a control panel into an IBM 407 Accounting Machine Another panel is on the floor nearby.
An 80-column punched card. Rows 0 to 9 are labeled. The 12 row, on top, has one punch in column 7. The 11 row, below it is not punched on this card. As cards passed through a read station, usually 9-edge (bottom edge) first, wire brushes, one for each column, would make contact through the holes.