View source for PDP-1 alphanumeric codes

{{FormatInfo
|formattype=electronic
|subcat=Character encoding
|released=1959
}}
The '''PDP-1 alphanumeric codes''' were used to encode text characters for input and output on a DEC PDP-1, a computer model that was available from 1959 to 1969. The introduction of this model predated the creation of [[ASCII]], so (as was common in the early computer industry) a proprietary coding was used.

Several different codings were used, actually; the manuals show at least three, Friden Code, FIO-DEC Code, and Concise Code. They each assigned different code points to the various letters, numbers, punctuation, and control characters. Concise codes were two-digit numbers, but were not always consecutive for letters of the alphabet; A through G were 61 through 67, but H was 70 and J was 41. Friden Codes used three digit numbers, while FIO-DEC codes used a mixture of two and three digit numbers, most of which were either equal to the Concise Code or to the Concise Code with another digit placed before it.

== Links ==
* [https://archive.org/stream/bitsavers_decpdp1F15_2666384/F15_PDP1_Handbook_Apr60#page/n15/mode/2up 1960 manual showing Friden and Concise codes]
* [https://archive.org/stream/bitsavers_decpdp1F17_28841238/F17_PDP1Maint_1962#page/n123/mode/2up 1962 manual showing FIO-DEC and Concise codes]

[[Category:Digital Equipment Corporation]]