Hot answers tagged

113

The text-mode cursor isn’t a character, it’s managed separately by the video output circuitry (which is how it keeps blinking even when your computer is busy or locked up). It can be enabled or disabled, and its size can be determined — at least, its start and end scanlines, which determine its height; the cursor always occupies the full width of a character ...


53

Old COBOL standards were based around 80-column punched cards, and columns beyond 71 (or 72) were reserved for line numbers. They were little used, but a numbered deck, if dropped, could be sorted by a collator. Because of this, some compilers would not parse beyond a certain column (which could be 70, 71, or 72). So, in the interests of compatibility, it ...


52

The cursor on the CGA, MDA, EGA, and VGA cards was a hardware sprite generated on the earlier cards by the 6845 video controller, and on later cards by a chip that emulates the 6845. That chip has an address counter that is used to fetch data from memory, as well as a line counter and a cursor-state latch. It also has a programmable registers for cursor ...


22

Why did the original Apple //e have two sets of inverse uppercase characters? Simple: To allow lower case inverse letters. It's all about the clever way Woz arranged the original II's single character set to save in hardware and offer additional functionality. There is only a single character set of 64 characters, showing up 4 times in 256 entry character ...


20

If you go back a lot before the x86, this technique wasn't unusual at all. In fact, writing programs using printable letters and symbols was pretty much the norm for early computers, except that there was a number of encodings for words of varying bit size, and that encoding was not ASCII. Examples: On the IBM 1401 (1959), a program that looked like ,...


20

Digital Research produced as one of their early attempts into graphical desktops (on their way to GEM) a basic portable graphics library - GSX. GSX did actually support proportional fonts, both in print and on-screen, and was included with the CP/M support in Amstrad machines running CP/M Plus. GSX was supported by two of DR's own applications, DR Draw and ...


17

In the old days, I remember we were told to never go beyond the 70'th column in the text editor (the actual value was usually something above 70, but less than 80). [...] If it makes a difference, this was when programming COBOL. No, it doesn't, as it was more of a feature of the underlaying priciples and standards for handling punch cards. By default ...


16

This is an AppleSoft issue where it puts spaces either side of a token. PET/CBM BASIC (based off the same code base) doesn't do this. Tokenising ignores spaces, this means it can be difficult on the PET to see some of the problems that the tokeniser can cause. For example LET AFOR=ONER gets parsed as LET A FOR = ON ER Which is very difficult to see on a ...


16

On the basis that a picture is worth a thousand words, I include my scan of a punched card: As amply described in the other answers, it shows how the columns are visibly marked on the card for different purposes. It makes sense when you see a card. It makes less sense when you're using a computer display or are using paper tape!


14

Just the first (of many) example of using proportional fonts on Commodore64: https://youtu.be/k2NRlsopoOU?t=441 You couldn't really use a proportional font on the Spectrum because the colour attributes were one background and one foreground for each 8x8 square. That meant that, practically speaking, each letter had to be by itself in an 8x8 cell. ...


11

It was standard practice on the Sinclair ZX80 & ZX81 to put executable code into a REM statement at the beginning of a BASIC program. REM statements are, of course, ASCII comments, so this meets your requirement for executable ASCII. The ZX80 (1980) and ZX81 (1981) predate your question about the early 1990s by about 10 years and used the Z80 processor....


10

Here is a program I wrote several years ago in AppleSoft for the fun of it. What it simply does is disassemble itself from the tokenized storage into a listing. If you run it, it will look the same as if you did a LIST command. In general, this gives you all the rules of AppleSoft formatting but in the form of a program :-) 0 REM ** DISASSEMBLE MYSELF 1 ...


10

No 8-bit computer (back then) did support proportional fonts out of the box, but there where some programs on next every bitmap capable 8 bit computer, I this might as well include the Spectrum. For the Apple II support was added by Apple rather early. Already the Apple DOS Toolkit included a utility called HRCG or High Resolution Character Generator, ...


10

Back in 1986, a company called Berkeley Softworks released a GUI desktop environment called GEOS for the Commodore 64. It was later ported to the Commodore 128, the Commodore Plus/4, and Apple II. GEOS was obviously inspired by the classic Mac OS desktop. It implements all the basic elements one would expect from such environment, such as a pointer-driven ...


9

ASCII was designed from the start with usable subsets (for instance an uppercase subset representable with six bits, consisting of the four central columns) and international variants. SHARE (IBM users' group) insisted that all characters needed for PL/I, included the vertical bar, were present in the uppercase subset(*). That was solved by allowing ! to ...


9

"Character memory" is the bitmapped definitions for each of the characters (e.g. "glyphs") that are displayed in text mode, based on the "character codes" that are poked into the "screen memory". Depending on which graphics mode you enable, there are several different memory areas that will be accessed by the VIC-II in creating the display. If we only focus ...


8

I remember doing this on the university mainframe around 1975. This was on an ICL1904S. Note that the 1900 series had been around for more than 10 years at that time. I don't know when the feature came out but it had been around for some time. You could list out any executable in card reader format. It would produce the executable in 6-bit characters in ...


7

The games Skool Daze and Back To Skool used proportional fonts for text on the ZX Spectrum. (source: worldofspectrum.org)


7

Short Answer It can be done in any environment that: Allows the remarking of data files into program files, Has a loader format that's either primitive enough or all readable Has a character set (doesn't have to be ASCII) that has a sufficient number of encodings that produce valid opcodes Has an address space layout that fits the possible encodings ...


6

From my experience, you have two options: Use a utility called "MacDisk For Windows" from (https://macdisk.com/mden.php) that has a good chance of allowing a PC that is equipped with a Floppy Drive (USB or Otherwise) to read the HFS or HFS+ Formatted Macintosh Disk you have. I've used this in the past with good results. If you are concerned about using ...


5

That's the ubiquitous 1.44MB 3.5" floppy. Any modern floppy drive should be able to read it; the hard part is finding software that understands the format -- Mac-formatted disks aren't readable by Windows. The first thing I'd try is plugging a USB floppy drive into a Mac and reading the disk directly: if you're lucky, everything should just work, and you ...


5

For a slightly interesting twist on this concept, consider Control Data mainframes. These beasts included not only a CPU, but a "peripheral processing unit" (PPU)1--and the CPU sent commands to the PPU via normal I/O channels. The CPU was a 60-bit processor that used 6-bit character codes. The PPUs were 12-bit processors, so the CPU sent a stream of 2 ...


5

The screen character set on the Apple II looks like this: 00-1f: ASCII 40-5f, but inverse text 20-3f: ASCII 20-3f, but inverse text 40-5f: ASCII 40-5f, but flashing text 60-7f: ASCII 20-3f, but flashing text 80-9f: ASCII 40-5f (officially control characters, but displayed as normal text) a0-bf: ASCII 20-3f c0-df: ASCII 40-5f e0-ff: ASCII 20-3f (Apple ][/][+)...


5

10 input "some question?"; name$ Will be reformatted as: 10 INPUT "some question?" ; NAME$ That's not quite right (confirmed just now with an emulator). It will be reformatted as: 10 INPUT "some question?";NAME$ i.e. there are no spaces before and after the semicolon. You can see what the formatting algorithm looks like in C++ in this ...


4

What are the rules for Applesoft BASIC formatting for code? The most basic thein to know is that there is no source code in the sense of plain text files. Only the tokenized basic lines. When listing a programm. The tokens get converted back to their (uppercase) keywords with spaces being added after each. This even adds some quirks when using screen ...


4

I assume your question is specifically about the 2741 - as otherwise the question would be way too broad (*1). The 2741 operated in a basic line mode using a simple handshake protocol to switch between sending and receiving (*2). Everything except the handshake characters was a possible input, thus BS as well. When in user input mode everything typed was ...


3

While the PC-98 became the dominant PC architecture in Japan (up until Windows 95 made it irrelevant) I don't think it had any significant advantage beyond BIOS support for Japanese. On the other hand, it had the significant disadvantage of being largely proprietary to NEC. IBM PC compatibles could made by anyone, including by a number of the Taiwanese ...


2

Punched cards were, of necessity, a fixed number of columns (80, with fixed column use dependent on the language. JCL, for example, used the entire card). Many programming languages introduced at that time had a fixed format in which the column a character appeared in was significant, much like the invisible significance of position in modern programming ...


2

The same question could be asked about other systems that where successful in their home country or region. Like the PC-D or the EuroPC in Germany, Amstrads 1512 in the UK (and somewhat on the continent) and several others. Even thru the markets thruout Europs where rather similar in their requirements, and the machiens did do well, none of them became an ...


2

On floppy media that was not sold as preformatted, the unformatted capacity was commonly stated. 2MB is the unformatted capacity of what is commonly called a 1.44MB floppy. However, the actual low-level format on the floppy could be: PC DD format, which is 360 or 720kB. A PC drive can physically read that. Mac 800kB/400kB format. A non-specialty PC drive ...


Only top voted, non community-wiki answers of a minimum length are eligible