114

Why is ASCII this way? First of all, there is no one best sorting order for everything. For example, should UPPER or lower case be first? Should numbers be before or after letters? Too many choices, and no way to please everyone. So they came up with specific pieces that "made sense": Numerals 0x30–0x39 - Easy bit mask to get your integer value. UPPER ...


63

It all dates back to typewriters, but the two layouts aren’t ASCII v. non-ASCII, they’re mechanical v. electric. The !" etc. layout was common on mechanical typewriters, based on the layout used for the Remington No. 2 in 1878. This is the layout that ASCII was based on; that’s why “!”, “"” etc. received consecutive encodings, aligned with the encodings of ...


60

According to ASA X3.4-1963 Appendix A, one of the design considerations was: (7) Ease in the identification of classes of characters Furthermore: A4.4 The character set was structured to enable the easy identification of classes of graphics and controls. And on page 8: A6.3 To simplify the design of typewriter-like devices, it is desirable that ...


52

While general purpose function keys are something that had already been introduced in the 60s by manufacturers like Friden (Flexowriter, 1965) or HP (9810A, 1971), it wasn't until IBM's 3270 that function keys were widely available. 3270 terminals are block-orientated, which means all keystrokes, thus all editing, are local. Only the whole screen can be sent ...


48

Even though the CR usually goes before the LF in ASCII text, most printer mechanisms actually perform the LF before, or during, the CR. So the shape of the arrow is actually accurate. This is even true of mechanical typewriters, in which the carriage is returned through a physical lever which, before enough force is transmitted through it to move the ...


40

I remember a conversation with an IBM engineer back in the 1980s, who implied there was an internal fight over this between IBM's engineering and marketing departments. The engineers wanted the PC to have the same keyboard as the popular 3270 mainframe terminal, for easy migration of users and software in a business environment, and in fact IBM did produce ...


40

The ← and ↑ symbols were originally included in ASCII-1963 as programming operators. They were used in a number of programming languages at the time, but the only common usage left today is in Smalltalk where the _ and ^ characters which replaced them in ASCII-1967 can still be used for variable assignments and variable selectors, respectively. The ...


39

Before IBM PC even existed, terminal keyboards for IBM Mainframes make extensive use of the SysRq or (System Request) key. I recall using SysReq key on IBM 5251 and 5291 terminals for IBM S/36. Probably the key (and function) was already present in the 1970s IBM 3270 terminal. Its function was to suspend the current job and display the System Request Menu. ...


36

The Space Cadet is a keyboard designed for use with Symbolics' Lisp Machines, and many of the extra keys are specific to that use. Starting from the bottom row: Hyper, Super, Meta and Ctrl are modifier keys, known as bucky keys; they are equivalent in use to the Ctrl, Alt and Alt Gr on modern keyboards (and to the Windows, context menu, Apple and Option ...


34

The Restore key triggered the NMI (non-maskable interrupt) line; to actually have an effect it had to be combined with Run/Stop - it would soft-reset the machine (via an indirect jump vector that could be overwritten to a custom routine if desired. This wouldn't reset memory, but would stop even misbehaving programs in most cases.) Run/Stop was two keys; ...


32

Chromatix answer already perfectly nails the technical background. Especially the reference to classic typewriter mechanics, predating any TTY or terminal, were the symbol used quite closely follows the hand movement when isueing a new line. Historically it may be interesting to look at the development. The combined function as a single key was only ...


28

SysRq is popular because the PC AT was popular, and its clones were too. PC clone manufacturers copied all the features of the computers they were cloning, with the exception of BASIC in ROM, and that included SysRq — both the physical key, and its associated handling in ROM (interrupt 0x15 function 0x85). Any OS or software running on the AT could end up ...


27

man 7 ascii of Linux Programmer's Manual says, Uppercase and lowercase characters differ by just one bit and the ASCII character 2 differs from the double quote by just one bit, too. That made it much easier to encode characters mechanically or with a non microcontroller-based electronic keyboard and that pairing was found on old teletypes. As ...


27

The official answer (at https://support.apple.com/kb/TA34988?locale=en_US) is that they pretty much made it up as they went along: At some time in Apple's history it was decided to put the "bumps" on the D and K keys while some other computer companies use the F and J keys. [...] Apple engineering has indicated there is no standard, such as ISO or ANSI ...


26

I did such interface long time ago. It was(is) an internal interface designed to fit in a place near the right side of the board when using the Plus case. Technical details here: http://www.zxprojects.com/index.php/ps2-adapter This is the board Designed to fit here: Schematic. Very simple. One microcontroller does all the work. Upon booting, the uC ...


25

In scancode set 2, the "break" scancodes consist of the "make" scancodes prefixed by F0. This is consistent across nearly all the keys. Some keys include a modifier prefix in the Ex range as well, and this is repeated in the "break" sequence. Additionally some keys behave as if two keys are pressed at once, and thus include multiple F0 codes to ensure ...


23

Personally I know this from a typewriter course in school (ca. 1973). The machines we used hat slightly different cavity on D/K to support touch-typing. we were supposed always rest our middle fingers there while having the rest afloat. A similar lesson was given for the use of adding machines with a similar keycap for the 5 key. But so far I couldn't find ...


22

I think the answer is Lotus 1-2-3. Working in a spreadsheet, you are going to want to be able to use the numeric keypad for quick numeric entry, and you are going to need to use the cursor keys to move around the spreadsheet. Having to continually hit the Num Lock to switch between "modes" would be a pain. I have no actual evidence to back this up, other ...


19

In the end, I decided that it had to be easier to take the keyboard apart than to de-solder the 4051's and so I carefully removed the 18 tiny screws from the back of the keyboard. It wasn't nearly as bad as I expected (I was concerned that I was going to have springs everywhere). After disassembly I fired up the Atari to try and see if I could get the A ...


19

Keyboard Switch On the International version Apple IIc the keyboard switch swiched between a country-specific layout and and a standard U.S. layout. On the USA version it switches between the standard QWERTY and a Dvorak layout. (This was not so much a desired feature as a side effect of having to build the European version with a keyboard switch; putting a ...


18

The ← and ↑ symbols are remnants of an earlier version of ASCII. The ← and ↑ have now been replaced with _ and ^ respectively.


18

I think you're coming at this kind of backwards. The commonly used keys are commonly used because they're on keyboards and are widely available. Software follows hardware in this instance. The system request key was put there because the hardware designers thought it would be useful, and even if they were wrong, removing keys from the standard keyboard as ...


16

This chart (showing the hexadecimal values of ASCII characters) outlines manassehkatz's answer graphically: Numbers are at 0x30 + the value of the number Capital letters are at 0x40 + the value of the letter (A=1, B=2 etc) Lowercase letters are at 0x60 + the value of the letter.


16

According to the Wikipedia article: The keyboard layout mirrored that of the Apple IIe; however, the “Reset” key had been moved above the “Esc” key. Two toggle switches were also located in the same area: an “80/40”-column switch for (specially written) software to detect which text video mode to start up in, and a “Keyboard” switch to select between ...


15

If the IBM Model M keyboard is one of the ones that uses the AT protocol, you may be able to use a passive 5-pin to PS/2 adapter, chained with an active PS/2 to USB converter such as the Belkin F5U119. If it uses another protocol (such as XT or 3270 terminal) you will need a custom-made active converter -- https://deskthority.net/wiki/Converter lists ...


15

Cost was certainly a part of it, but sound was another. Mechanical switches make more noise than rubber-dome and electromechanical, and as computers became more of a fixture in houses (and offices), I think that this became an issue. The fact that mechanical switches cost a lot more was probably the deciding factor, though.


15

As things become cheaper, people learn to tolerate lower and lower quality.  This happens in many fields of endeavor.  The voice quality people tolerate from today's mobile phones would have been generally unacceptable to land-line telephone engineers in the 1990s.  The typographic spacing people have learned to to from automated typesetting ...


15

As other answers and comments have already said, the SysRq key was first introduced with the keyboard of the PC/AT of 1984, and had parallels to similar keys on IBM mainframe keyboards. Even if it was rarely used, keyboard manufacturers kept including it, as removing it would make their keyboard incompatible with the few pieces of software that did use it. ...


14

I believe the C64 keys were carried over from the VIC-20. The VIC-20 keys (somewhat at least) have some history from the PET series too. Taken from Wikipedia on the VIC 20: When they returned to California from that meeting, Tomczyk wrote a 30-page memo detailing recommendations for the new computer, and presented it to Tramiel. Recommendations ...


14

I just want to add to the existing answers that the Restore key was a weird key. It was on hardware side already completely independent of all the other keys. It was attached to the NMI line of the processor, only proxied by a small circuit which let only rising flanks pass. This circuit sometimes ignored a simple slow press and reacted much more reliably ...


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