New answers tagged

1

Answering one of your questions "When did ASCII become a worldwide standard", the answer is: never. The "A" stands for "American". At the time the US adopted ASCII, other countries were adopting their own variants, substituting different characters according to national needs: for example in the UK, "£" was substituted ...


2

I'm going to provide a terrible answer, but include a couple references that might be great for nostalgia. One is NostalgiaNerd on youtube, he provides a British viewpoint of IBM's shift to ASCII (OK they only did it through codepages, not really fully/completely ASCII). The video is strangely titled, nothing about ASCII or EBCDIC in the name: "These ...


18

TL;DR: ASCII was never intended for processing, just as an interface standard for data exchange (hence the name American Standard Code for Information Interchange) IBM never switched, it still uses EBCDIC within mainframes and ASCII for communication. IBM was a major proponent for ASCII, but not the sole force, and especially not international. ASCII soared ...


3

In the 1960s, IBM used a crazy variety of character codes. IBM was the king of punched cards, commonly known as "IBM cards", so many codes related to the sparse 12 bit codes used for those. However, even these were not fully standardized: different keypunch models used different character sets! 6-bit BCDIC was designed to easily map to the most ...


1

According to wiki IBM System 360 had byte addressable RAM. Yes. [Considering this and the title "Why did IBM System 360 have byte addressable RAM" it feels as there's a mixup about what addressing and RAM means. See some thoughts about that at the end)] Previously IBM had machine with word addressable memory. No. Only very few. IBM did make all ...


19

IBM started using ASCII before 1970; the 2260 terminal, released in 1964, used the unpublished (but ratified) 1965 version of the ASA X3.4 standard. IBM mainframes still use EBCDIC, so I don’t think their popularity had much bearing on the popularity of ASCII (but other encodings’ popularity influenced IBM mainframes: their instruction set includes ...


2

Did they have any performance improvements for such decision? If so, why do we have 8-bits registers today? Most 32-bit non-x86 CPU types today still only have 32-bit registers but they can access memory byte-wise. Examples are ARM, MIPS, PowerPC, Sparc, TriCore, RH850, SH CPUs and there are a lot more. So your observation is not something which is typical ...


1

Programmers do need to process characters from memory, and characters are generally smaller than the machine word. The architectural possibilities seem to be: Instructions that only read/write words. Programmer must use explicit shift, mask, logical-or to operate on characters. There are special instructions that use a "character address" that ...


0

The 360 was designed as an all-purpose system. That means that among other things, it should be suitable for processing text. Nowadays, a computer for processing text could perfectly well go with 32 bit addressing unit and take the attitude that you always use Unicode, but in those days Unicode didn't exist and it would've been too expensive to use 32 bits ...


11

Why did IBM System /360 have byte addressable RAM, but didn't have 8 bits registers These issues are unrelated. Registers are about addressing, so they need to hold an address word. Byte addressable RAM in turn is needed to handle bytewide data - most notable characters and strings. There is no inherent need that a CPU must have byte sized registers as well....


6

There is no downside I can see to storing an 8-bit quantity in a 32-bit register if you already have the 32-bit register. Load/store take the same amount of time. Memory transfers are at least word-sized (maybe larger) anyway. Arithmetic in general is not faster on smaller binary numbers. You'd need more opcodes or addressing modes, potentially consuming ...


Top 50 recent answers are included