http://fileformats.archiveteam.org/api.php?action=feedcontributions&feedformat=atom&user=Sgeo 2026-04-05T16:38:07Z User contributions MediaWiki 1.19.2 http://fileformats.archiveteam.org/wiki/PDP-1_alphanumeric_codes 2025-06-20T22:45:44Z

<p>Sgeo: Oops</p> <hr /> <div>{{FormatInfo<br /> |formattype=electronic<br /> |subcat=Character encoding<br /> |released=1959<br /> }}<br /> 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.<br /> <br /> 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.<br /> <br /> == Links ==<br /> * [https://archive.org/stream/bitsavers_decpdp1F15_2666384/F15_PDP1_Handbook_Apr60#page/n15/mode/2up 1960 manual showing Friden and Concise codes]<br /> * [https://archive.org/stream/bitsavers_decpdp1F17_28841238/F17_PDP1Maint_1962#page/n123/mode/2up 1962 manual showing FIO-DEC and Concise codes]<br /> <br /> [[Category:Digital Equipment Corporation]]</div>

Sgeo http://fileformats.archiveteam.org/wiki/PDP-1_alphanumeric_codes 2025-06-20T14:39:18Z

<p>Sgeo: Explanation of Concise code &lt;-&gt; FIO-DEC</p> <hr /> <div>{{FormatInfo<br /> |formattype=electronic<br /> |subcat=Character encoding<br /> |released=1959<br /> }}<br /> 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.<br /> <br /> 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.<br /> <br /> == Links ==<br /> * [https://archive.org/stream/bitsavers_decpdp1F15_2666384/F15_PDP1_Handbook_Apr60#page/n15/mode/2up 1960 manual showing Friden and Concise codes]<br /> * [https://archive.org/stream/bitsavers_decpdp1F17_28841238/F17_PDP1Maint_1962#page/n123/mode/2up 1962 manual showing FIO-DEC and Concise codes]<br /> <br /> [[Category:Digital Equipment Corporation]]</div>

Sgeo http://fileformats.archiveteam.org/wiki/PDP-1_alphanumeric_codes 2025-06-20T14:25:07Z

<p>Sgeo: Octal clarification</p> <hr /> <div>{{FormatInfo<br /> |formattype=electronic<br /> |subcat=Character encoding<br /> |released=1959<br /> }}<br /> 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.<br /> <br /> 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.<br /> <br /> == Links ==<br /> * [https://archive.org/stream/bitsavers_decpdp1F15_2666384/F15_PDP1_Handbook_Apr60#page/n15/mode/2up 1960 manual showing Friden and Concise codes]<br /> * [https://archive.org/stream/bitsavers_decpdp1F17_28841238/F17_PDP1Maint_1962#page/n123/mode/2up 1962 manual showing FIO-DEC and Concise codes]<br /> <br /> [[Category:Digital Equipment Corporation]]</div>

Sgeo