Applications
The PDS-1 and PDS-4 were bought in small numbers by R&D organizations and many universities. They developed pioneering computer applications and trained the next generation of graphics system designers. The FRESS hypertext system had enhanced capability and usability if accessed from a PDS-1 system; the user could make hyperlinks with a light pen and create them simply with a couple of keystrokes. Multi-window editing on FRESS was also possible when using the PDS-1. PDS-1 systems were used to design Arpanet's network graphics protocol.
Imlac display systems were bundled into various larger commercial products involving visual design and specialized software. Imlac sold a newspaper layout and typesetting system using PDS-1 called CES. MCS's Anvil mechanical CAD system used later Imlac workstations to interactively design mechanical parts, which were then milled out automatically from metal stock.
Some simple applications such as text editors were entirely coded in Imlac assembler and could run without much involvement with a larger computer. Hofstadter composed his book Gödel, Escher, Bach on an Imlac editor. But most graphics applications required strong floating point support, compilers, and a file system. Those applications ran mostly on an expensive timeshared computer, which sent digested image data to the Imlac, which ran a small assembler program emulating a generic graphics terminal. A typical use was rendering architectural drawings and animated walkthroughs that had been previously drawn offline. PDS-1 use was held back for several years by not having a standard program library supporting animation or interactive drawing and dragging of objects.
But at night time, students were willing to write large amounts of assembler code just for fun. The PDS-1 applications most remembered today are the early interactive games. The two-player Spacewar! was ported from a PDP-1 demo. Frogger was created on a PDS-1 as part of a psychology experiment and then became a popular video arcade game. Mazewar, the first online multiplayer computer game, was created on a pair of PDS-1's. Later, up to 8 players ran on PDS-1 stations or other terminals networked to the MIT host PDP-10 computer running the Mazewar AI program. Mazewar games between MIT and Stanford were a major data load on the early Arpanet.
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