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The Altair 8800 had a set of switches on the front panel which could be used to store arbitrary data to arbitrary bytes of RAM. The designers of the Altair published a boot loader that was IIRC a lit …

The first CMOS microprocessor, the CDP1802, has a 4-bit "X" register which is used to select one of 16 registers for use with many opcodes including those for arithmetic and bitwise operations. That …

Given a function declaration like void far copyAnywhere(void far *dest, void far *src, unsigned len); it will be usable from within any memory model except huge. If called from within e.g. small m …

A handy way of outputting a string on the Z80 is to use something like: primm: ex (sp),hl primmlp: ld a,(hl) call putchar inc hl ld a,(hl) or a jr nz,primmlp ex (sp),hl ret The mess …

The normal way to handle cross-bank calls is to use a springboard which is either in an unbanked area of memory or appears identically in both old and new areas. If one doesn't mind using a different …

I suspect the biggest benefit of a frame pointer comes when a program mixes a high-level language with in-line assembly or machine code [as was much more common in the 6809's heyday than it is now]. …

The JR instructions are slow when the branch is taken because they use a four-bit(!) ALU to compute the new address. This calculation can't start until after the target address is fetched (which it a …

Nowadays it's common to handle such things using linkers that allow section logical and load addresses to be specified separately, but for projects that are built using a single assembly-language file …

Back in the day, it meant that present versions of the Commodore BASIC and Kernel did not use those locations, but Commodore said nothing about whether future versions of the ROM might do so. Address …

Some macro assemblers have a macro construct which performs text substitution within a line, some have features that allow a line to be replaced with a sequence of lines, and some have both. The two …

If one can divide the program into a number of sections of 64K or less, and can assign global sequential indices to every cross-section entry point, one could produce a table in the data segment wiht …

Although the instructions LSR, ROR, ASL, and ROL were described as having five addressing modes that include "accumulator mode", each of them should really be thought of as two instructions, e.g. "LSR …

It may be worth noting that in the early days of computing, many documents consisting entirely of human-language text which was intended to be read solely by humans were reproduced in all caps. Photo …

If one writes opcodes in binary, using the format III-AAA-gg (with "III" generally being "Instruction", "AAA" being "Address mode", and "gg" as "general instruction group"), most instructions of the f …

An aspect of development which hasn't yet been mentioned is that many games are developed using what are called "domain specific languages", which are often tailored around the particular needs of a g …