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The PDP-1 (Programmed Data Processor-1) was the first computer in Digital Equipment Corporation's PDP series and was first produced in 1960. It is famous for being the computer most important in the creation of hacker culture at MIT, BBN and elsewhere. The PDP-1 was also the original hardware for playing history's first game on a minicomputer, Steve Russell's Spacewar!.



It has an 18-bit word and had 4 kilowords as standard main memory (equivalent to 9 kilobytes, or 9,000 bytes), upgradable to 64 kilowords (144 kB). The magnetic core memory's cycle time was 5 microseconds (corresponding very roughly to a "clock speed" of 200 kilohertz; consequently most arithmetic instructions took 10 microseconds (100,000 operations per second) because they had two memory cycles: one for the instruction, one for the operand data fetch. Signed numbers were represented in one's complement.

The PDP-1 was built mostly of DEC 1000-series System Building Blocks, using Micro-Alloy and Micro-Alloy-Diffused transistors with a rated switching speed of 5 MHz.


The PDP-1 used punched paper tape as its primary storage medium. Unlike punched card decks, which could be sorted and re-ordered, paper tape was difficult to physically edit. This inspired the creation of text-editing programs such as Expensive Typewriter and TECO. Because it was equipped with online and offline printers that were based on IBM electric typewriter mechanisms, it was capable of what, in eighties terminology, would be called "letter-quality printing" and therefore inspired TJ-2, arguably the first word processor.

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