Glossary
Terms this guide uses, in the sense this guide uses them. Where a word means something slightly different in the wider world, that is noted.
ACIA — the serial chip, a 65C51. Turns bytes into the stream of pulses that goes down the serial cable, and back again.
ACE — All-in-one Computer Experience. The machine this guide is about: one board carrying the processor, memory, video, sound, storage, serial, clock, joystick ports and a full keyboard. See The ACE.
ARMSID — the sound chip. A modern part that behaves like the MOS 6581 "SID" from the Commodore 64: three voices, real filters, RCA out.
bank — one 1 KB slice of the 512 KB of extra RAM. Only one is visible at a time, through a window at $8000. BANK n picks which. See Banked RAM.
BASIC — the language the machine boots into, and the program in ROM that runs it. Version 2.0 here. See Programming in BASIC.
BIOS — the whole 32 KB of ROM: Kernal, BASIC and Wozmon together. This guide describes BIOS v2.0. Not the same sense as a PC's BIOS, which is only a boot loader.
CompactFlash — the storage card. Behaves as an 8-bit IDE drive; the BIOS divides it into 256 disks of 1 MB each. See Storage.
cartridge — a ROM on a small board that drops into the slot behind the keyboard and takes over $C000–$FFFF, replacing BASIC and Wozmon. See Writing a cartridge.
CP437 — the character set, from the original IBM PC, carried by the video card rather than the ROM. Box drawing, card suits, Greek letters, three densities of shading. See The character set.
break report — what the machine prints when a program reaches a BRK: the address, the break number and every register, then the OK prompt. See Reaching the machine.
cold start — power off and on again. Memory is cleared, BASIC starts from nothing. Compare warm start.
disk — one of the 256 1 MB partitions on the CompactFlash card, each holding up to sixteen files. DISK n selects one. Nothing to do with a spinning disk.
GPIO — general-purpose input and output, the sixteen pins of the 65C22 VIA. The joysticks and the keyboard use them; so can you.
immediate mode — typing a line without a number in front, so it runs right away. Compare program mode. See Typing it in.
jump table — the first 256 bytes of the Kernal, a fixed list of three-byte jumps. Calling one of those addresses is how a program asks the machine to do something, and the addresses do not change between ROM versions. See The Kernal.
Kernal — the ROM routines that drive the hardware: printing, reading keys, files, sound, the clock. Spelled with an a, following Commodore's original typo. See The Kernal.
layer — one of the video card's two grids of tiles, drawn one over the other and scrolled separately. Text is layer 0. See The graphics modes.
KIM — a 1976 single-board computer, and here the three-board add-on built in its likeness: a hex keypad, a two-line display, and a monitor ROM of its own. It works the way the original worked; it does not run the original's software.
null modem — a serial cable or adapter that crosses transmit and receive. The ACE and a PC are both wired as terminals, so reaching one from the other needs one. See Connectors.
NVRAM — 256 bytes inside the clock chip, kept alive by its battery. The one place a program can leave something behind with the power off.
palette — the 256 colors the video card can show at once, each picked from 4,096. The first sixteen are the colors COLOR numbers. See The graphics modes.
pen — the pair of colors, letters and background, that the next character printed is drawn in. COLOR sets it; what is already on the screen keeps its own. See The screen.
PICO9918 PRO — the board the video card is built on: a Raspberry Pi RP2354 with a VGA socket, running the PICOVDP firmware. The earlier Pico9918 boards, built on the RP2040, behave as a TMS9918A and belong to the BIOS 1.6 edition of this guide.
PICOVDP — the video chip: firmware written for this family, giving text with a color per character, four screen layouts up to 320 × 240, two layers, 256 colors and 64 sprites. See The screen.
port B — the video card's second pair of addresses, $9C02–$9C03. The Kernal and BASIC use the first pair, so an interrupt handler that uses port B never trips over them. See Interrupts.
program mode — typing a line with a number in front, so it is stored rather than run. RUN runs what is stored. Compare immediate mode.
prompt — the OK and the blinking cursor: the machine telling you it is your turn.
PRG — a program file with a two-byte load address on the front. What SAVE writes and LOAD reads.
save slot — one of 16 slices of the NVRAM, 16 bytes each: an owner ID, a checksum and 14 bytes of save. Programs that keep to the slots can share the clock card. Not the same as a slot. See The clock and Time and memory that lasts.
sprite — a small picture the video card draws over the layers at any position, without disturbing what is underneath. There are 64. See The graphics modes.
slot — one of the eight 1 KB windows between $8000 and $9FFF, one per piece of hardware. The machine works out at power-on which ones answer. See What's fitted.
token — the single byte BASIC stores in place of a keyword. FOR is one byte in memory and three characters on the screen, which is why LIST has to translate. See What BASIC does with your memory.
VIA — Versatile Interface Adapter, the 65C22. Two 8-bit ports and two timers. Runs the keyboard and the joysticks here.
warm start — pressing the reset button. BASIC starts again from the top, but memory isn't cleared, so your program survives and only its variables start over. This is the safe way out of a program that has run away. Compare cold start.
Wozmon — Steve Wozniak's monitor from the Apple I, 250 bytes long, kept at $FF00 as an easter egg. SYS 65280 from BASIC gets you there and C000R brings you back.
XModem — the file-transfer protocol the serial port speaks. LOAD and SAVE with no filename use it. See Serial and a terminal.
zero page — the first 256 bytes of memory. The processor reaches them with shorter, faster instructions, so they are valuable. The Kernal owns the first 58; the rest are yours, though not while BASIC is running. See The memory map.