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Retrocomputing

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    Often, clearing the other 24 bits of the register was unnecessary, even when you wanted to do arithmetic on character data if you only cared about 8 bits of the final result. And using the "translate" and "translate and test" instructions, you could often operate on character data without doing explicit arithmetic or using AND/OR type logic to twiddle individual bits.
    – alephzero
    Commented Jul 7, 2020 at 13:37
  • @alephzero :) sure, these are the detailed ways to handle it, still not changing the fact that registers weren't really meant for character handling at all.
    – Raffzahn
    Commented Jul 7, 2020 at 13:45
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    All of the above string instructions plus don't forget TR and TRT - super powerful, with applications beyond the obvious.
    – davidbak
    Commented Jul 7, 2020 at 14:38
  • @davidbak and CLCL and MVO/N (yes, it can be used beside BCD) and so on. TR(T) is an extrem versatile beast when combined. Want to test a string for certain characters? Make up a table with an entry for each character with the bits for attributes (like alpha, case, num, punctuation, whitespace) and translate a copy using a single TR String,Tab. Then OR it together using a single OC String+1(len-1),String and the last byte will contain the combined attributes. Use NC alike. And that's only the start. Building parsers can be done in a few machine instructions. Who needs so called HLLs?
    – Raffzahn
    Commented Jul 7, 2020 at 14:49
  • The 8088's register set allowed assembly-language programmers to use six general-purpose 16-bit registers, or five general-purpose 16-bit and two 8-bit, or four 16-bit and four 8-bit, three 16-bit and six 8-bit, or two 16-bit and eight 8-bit registers. This was very handy for when writing assembly-language code for tasks which needed more than six registers, but didn't need them all to be capable of holding more than eight bits, but compilers for high-level languages didn't really attempt to exploit this.
    – supercat
    Commented Jul 7, 2020 at 17:17