Wikipedia:Reference desk/Archives/Computing/2021 April 30

= April 30 =

How do I turn my Right Alt key into a dead key?
The Bangla Keyboard Layout Jatiya has three mode normal, Shift and Righ Alt+Shift. https://commons.wikimedia.org/wiki/File:KB-Bengali-National.svg

I recently found out about dead keys Dead key. Is there any way I can make a layout that makes the right alt key a dead key on Linux(PopOS, ubuntu based). I think it will significantly bring my Bangla and English typing speed close. --Greatder (talk)

etymology of a directory in computing
Just curious about the etymology of Directory (computing) when was the first use in computing terms. List of computer term etymologies has nothing. I'm assuming it derives from books like a Telephone directory but I've no source? --Salix alba (talk): 05:51, 30 April 2021 (UTC)
 * Sorry, maybe I'm being obtuse, but why wouldn't it just be derived from the general definition of a directory: a structured listing of names, address, etc.? I wouldn't expect there to be a specific etymology for terms like "user name" or "credentials" or "directory", since the earlier usages are not that different in function than the computer versions, even if the format may be distinct. A computer directory and Pigot's Directory are not terribly different things. Matt Deres (talk) 19:27, 30 April 2021 (UTC)


 * The term was definitely used in 1965 for the file system of Multics. I don't know if this was the earliest use in the computing context, but the Multics file system was one of the earliest file systems, and rather innovative in introducing a hierarchical directory structure instead of a one-level structure with a single master index, one of many features of Multics that was copied by UNIX. Peter G. Neumann's SRI web page lists an email address – perhaps he can tell more. --Lambiam 22:16, 30 April 2021 (UTC)

Directory (computing) says that early computing systems had only a 'flat' file system. The 'Folder' concept of a hierarchical file system was introduced on ERMA in 1958.

Is it a Directory, a List, or a Catalogue? find  - info about IBM's Catalogs, again much the same concept under a different name.

CS 537 Notes, Section #25: Directories (Uni of Wiscon-Madison Computer Sciences Department CS 537) mentions DEC's TOPS-10 of 1967 as using directories, named as such. The DECsys (Technical Notes on DECsys) was introduced in 1965, using a PDP-7 and DECtape which apparently supported directories: The DECtape article says it was introduced for the PDP-1 and PDP-4 in March and May 1963 respectively, and later on the PDP-7. The DECtape was based on the LINCtape device  This storage device was first used with the LINC of 1962, perhaps the first minicomputer (alas no refs for the LINCtape section in our article.) DEC was involved with the LINC because it was built using DEC Systems Modules, and DEC starting manufacturing LINCs from the original 1963 design. (Bell et al, p. 175 The 1964 PDP-6 Monitor (a core resident collection of programs for controlling the operating environment) used DECtape, which "was a 128-word/block, block-addressable medium of 450 Kcharacters for which a file system was developed. Memory minimizing led to very sparing use of shared tables. The key global variable data was restricted to: core allocation table, clock queue, job table, linked buffers for Teletype and other buffered I/O devices (e.g., DECtape directory), and a directory of system programs and Monitor facilities.([Bell et al, p. 503)

So, it appears that the term directory was actually used by DEC from at least 1963, and probably by the LINC when referring to the file system from 1962. All these tape systems were formatted in addressable fixed-sized blocks, which I think allows certain blocks to act as tables as pointers to 'files' which (I think) in Unix terms at least point to inodes. Going back even further, the LINCtape was based on the tape drive for the TX-2 Tape System, released in around 1958, which according to this site was also block-addressable. I can't find any reference to the specific term 'directory' in this context. The last site links to a very readable memoir (but no text search) by Wesley A. Clark who co-designed the LINC - the TX-2 tape drive is mentioned on p. 138 [pdf 6]. Check out the first cat connected to a computer...

Which all ends up at The Evolution of the Unix Time-sharing System* by Dennis M. Ritchie who worked at Bell Labs on Multics. "...it was not until well into 1970 that Brian Kernighan suggested the name `Unix,' in a somewhat treacherous pun on `Multics,' the operating system we know today was born." MinorProphet (talk) 12:25, 7 May 2021 (UTC)


 * DEC's Files-11 ODS (On Disk Structure) starts at LBN 0 with INDEXF.SYS. This file contains a boot block, then several home blocks containing information about the volumes structure, a file bitmap and then the file headers.  These headers fulfill the same purpose as inodes and each describes the file's structure (including its primary name) and location on disk.  A file header therefore is analogous to, but not identical to, an inode.  The headers are found within INDEXF.SYS by offset using the FID (File IDentification number).  At its simplest a directory consists of consecutive records each of which contain minimal information, the file's name (in this directory) and the FID.  A lookup therefore reads the directory, obtains the FID and then goes to INDEXF.SYS to find the file details and layout.  The TU58/DECtape had the same structure.  The tape started with INDEXF.SYS and the files were laid down in subsequent blocks.  In passing, it was important to record the wanted files in the order in which they would be used to reduce tape rewinds.  On the VAX 11.730 and VAX 11/750 the console boot devices was a TU58 and the boot block contained the BOOT58 program that enabled the machine to read the rest of the console tape.
 * Thanks, Martin, really clear and interesting info. At least Mercury delay tubes had gone out of fashion... MinorProphet (talk) 17:20, 7 May 2021 (UTC)