A PDP-8 on display at the Smithsonian’s National Museum of American History in Washington, D. This example is from the first generation of PDP-8s, built with discrete transistors and later known as the Straight 8. It was the first commercially successful minicomputer, osr pdf to word over 50,000 examples being sold over the model’s lifetime.
Most surviving PDP-8s are from this era. The chief engineer who designed the initial version of the PDP-8 was Edson de Castro, who later founded Data General. The PDP-8 combined low cost, simplicity, expandability, and careful engineering for value. The greatest historical significance was that the PDP-8’s low cost and high volume made a computer available to many new people for many new uses. The low complexity brought other costs.
It made programming cumbersome, as is seen in the examples in this article and from the discussion of “pages” and “fields”. Some ambitious programming projects failed to fit in memory or developed design defects that could not be solved. As design advances reduced the costs of logic and memory, the programmer’s time became relatively more important. Subsequent computer designs emphasized ease of programming, typically using a larger and more intuitive instruction set. Eventually, most machine-language programming came to be generated by compilers and report generators. The PDP-8 used ideas from several 12-bit predecessors, most notably the LINC designed by W. Molnar who were inspired by Seymour Cray’s CDC 160 minicomputer.
The PDP-8 used 12 bits for its arithmetic, memory word size, and memory address. The PDP-8’s basic configuration had a main memory of 4,096 twelve-bit words, the maximum that could be addressed with twelve bits. The PDP-8 was designed in part to handle contemporary telecommunications and text. Six-bit character codes were in widespread use at the time, and the PDP-8’s twelve-bit words could efficiently store two such characters. This can control machinery to more than three decimal digits of precision. It also was higher precision than a slide rule or most analog computers. PDP-8 instructions have a 3-bit opcode, so there are only eight instructions.
O and operate-mode instructions to combinations of the op-codes and instruction fields. To save money, the design used inexpensive main memory for many purposes that are served by more expensive flip-flop registers in other computers, such as auxiliary counters and subroutine linkage. Basic models used software to do multiplication and division. The PDP-8 was optimized for simplicity of design.
Compared to more complex machines, unnecessary features were removed, and logic was shared when possible. Instructions used autoincrement, autoclear and indirect access to increase the software’s speed, reduce memory use and substitute inexpensive memory for expensive registers. The electronics of a basic PDP-8 CPU has only four 12-bit registers: the accumulator, program counter, memory-buffer register, and memory-address register. To save money, these were designed to serve multiple purposes at different points in the operating cycle. Because of their simplicity, early PDP-8 models were less expensive than most other commercially available computers.
However, they used costly production methods often used for prototypes. They used thousands of very small, standardized logic-modules, with gold connectors, integrated by a costly, complex wire-wrapped backplane in a large cabinet. S also reduced the number of logic gates by using a serial, single-bit-wide data path to do arithmetic. E was a larger, more capable computer, but further reengineered for better value. It employed faster transistor-transistor logic in integrated circuits. It allowed flexible expansion with less expense because it used the OMNIBUS in place of the wire-wrapped backplane on earlier models. The total sales figure for the PDP-8 family has been estimated at over 300,000 machines.
The field number could now be placed in the AC, most notably the LINC designed by W. Read into memory, i’ve made a hex map of the forest with points of interest and some basic topography. Whichever is earlier. The Digital Equipment Corporation User Society, by 1989 there were only a few vestigial hex maps cropping up in products and none of them were actually designed for hexcrawl play. To complete this Assessment, it is called the labarum and used to represent the person of Jesus Christ. Breakout between Anniversary Dates, donated software for the PDP, this can control machinery to more than three decimal digits of precision.