PDP-1 alphanumeric codes - Revision history

Sgeo: Oops

2025-06-20T22:45:44Z

Oops

Sgeo: Explanation of Concise code <-> FIO-DEC

2025-06-20T14:39:18Z

Explanation of Concise code <-> FIO-DEC

Sgeo: Octal clarification

2025-06-20T14:25:07Z

Octal clarification

Jsummers: Category:Digital Equipment Corporation

2016-03-11T20:20:05Z

Category:Digital Equipment Corporation

Jsummers at 22:20, 4 March 2016

2016-03-04T22:20:42Z

Dan Tobias: Created page with "{{FormatInfo |formattype=electronic |subcat=Character Encodings |released=1959 }} The '''PDP-1 alphanumeric codes''' were used to encode text characters for input and output o..."

2014-04-28T23:40:36Z

Created page with "{{FormatInfo |formattype=electronic |subcat=Character Encodings |released=1959 }} The '''PDP-1 alphanumeric codes''' were used to encode text characters for input and output o..."

New page

{{FormatInfo
|formattype=electronic
|subcat=Character Encodings
|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]

@@ Line 6: / Line 6: @@
 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 octal numbers (6 bits), 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. FIO-DEC codes are the same as Concise codes, with an extra bit (octal 20) to ensure the number of 1 bits is odd. (e.g. concise code 61 is FIO-DEC 61 as that has 3 bits on, and concise code 63 is FIO-DEC 263, as octal 63 has 4 bits on). This serves as a parity bit that a program reading in FIO-DEC encoding can check.
+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 octal numbers (6 bits), 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. FIO-DEC codes are the same as Concise codes, with an extra bit (octal 200) to ensure the number of 1 bits is odd. (e.g. concise code 61 is FIO-DEC 61 as that has 3 bits on, and concise code 63 is FIO-DEC 263, as octal 63 has 4 bits on). This serves as a parity bit that a program reading in FIO-DEC encoding can check.
 == Links ==

@@ Line 6: / Line 6: @@
 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 octal 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.
+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 octal numbers (6 bits), 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. FIO-DEC codes are the same as Concise codes, with an extra bit (octal 20) to ensure the number of 1 bits is odd. (e.g. concise code 61 is FIO-DEC 61 as that has 3 bits on, and concise code 63 is FIO-DEC 263, as octal 63 has 4 bits on). This serves as a parity bit that a program reading in FIO-DEC encoding can check.
 == Links ==

← Older revision		Revision as of 20:20, 11 March 2016
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	* [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_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]		* [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]]

@@ Line 1: / Line 1: @@
 {{FormatInfo
 |formattype=electronic
-|subcat=Character Encodings
+|subcat=Character encoding
 |released=1959
 }}