Glossary

Below is a list of commonly-referenced computing and programming terms found throughout the Better Bally Book. Sources are listed in parentheses after each entry, and source citations are listed at the bottom of the page.

accumulator: A temporary register where results of calculations may be stored by the central processor. (SC:325)

assembler: A program that converts symbolic instructions into machine macro-instructions. (SC:325)

BCD:

bootstrap: A program that coordinates the minimum amount of necessary peripherals to load a larger program into the computer. (SC:113)

debounce:

dope vector: “A data structure used to hold information about a data object, e.g. an array, especially its memory layout…The dope vector includes an identifier, a length, a parent address, and a next child address.”
Source: Dope vector

endian:

flag: A bit attached to a word for identification or for the purpose of signaling some condition. Typical microprocessors include carry, zero, sign, overflow, and half-carry status flags. (SC:326)

framebuffer: “A framebuffer (frame buffer, or sometimes framestore) is a portion of RAM[1] containing a bitmap that is driven to a video display from a memory buffer containing a complete frame of data.”
Source: Framebuffer

high-order: The highest place value in a given block of data.

instruction: A step in a program that defines an operation together with the address(es) of any data needed for the operation. (SC:326)

interrupt: A break in the execution of a program usually caused by a signal from an external device. (SC:326–7)

interrupt page address register (I): An 8-bit register that can be loaded with a page address of an interrupt service routine. During a mode 2 interrupt program, control will vector to this page address. (SC:29)

least significant bit: The binary digit occupying the right-most position in a number or word, usually 2⁰ or 1. (SC:327)

light pen: Photosensitive device that can be used to change the display on a CRT by generating a pulse at the point of contact. (SC:327)

low-order: The lowest place value in a given block of data.

Machine language: Sets of binary integers that may be directly executed as instructions by the microcomputers without prior interpretation. (SC:327)

microcomputer: A logical machine that manipulates binary numbers (data) and processes this information by following an organized sequence of program steps referred to as instructions. Includes a central processor, often contained on a single chip, memory, I/O devices, and power supply. (SC:21, 327)

microprocessor: The single integrated circuit around which a microcomputer is constructed. The microprocessor is a device (e.g., the Z80); the microcomputer is a system (e.g., the Bally Arcade). (SC:22)

monitor: A program that controls the operation of basic routines to optimize computer time. Also see 'operating system.' (SC:327)

Most significant bit: The binary digit occupying the left-most position in a number or word, usually 2⁷ or 128. (SC:327)

operating system: Software that operates the hardware resources of a microcomputer. The operating system may do scheduling, debugging, I/O control, accounting, compilation, storage assignment, and data management. (SC:327)

program counter (PC): Contains a 16-bit address in memory from which the current instruction will be fetched. Following execution of the instruction, the PC counter is either incremented, if the program is to proceed to the next byte in memory, or the present PC contents are replaced with a new value, if a jump or call instruction is to be executed. (SC:28)

reentrant: “In computing, a computer program or subroutine is called reentrant if it can be interrupted in the middle of its execution and then safely called again (“re-entered”) before its previous invocations complete execution.”
Source: Reentrancy (computing)

register: A memory device directly accessible by the central processor used for the temporary storage of a computer word during arithmetic, logical, or I/O operations. (SC:327–8)

read-only memory (ROM): Storage which can be written into only once. The information is fixed and cannot be changed. A ROM is usually mask programmed by the manufacturer and is bought with a preset bit pattern. ROM is used to store specific, unchanging programs steps or data. (SC:112)

scratchpad:

semaphore: “A variable or abstract data type used for controlling access, by multiple processes, to a common resource in a concurrent system such as a multiprogramming operating system. A trivial semaphore is a plain variable that is changed (for example, incremented or decremented, or toggled) depending on programmer-defined conditions. The variable is then used as a condition to control access to some system resource.”
Source: Semaphore (programming)

stack: A reserved area of several memory locations, the top of which is indicated by the contents of the stack pointer. Memory location are organized as a last-in, first-out file. By looking at particular entries in the stack, the central processor returns to a main program regardless of the depth of nested subroutines. (SC: 28-9)

vector:

Word: A set of bits that occupies one storage location and is treated as a unit. May have any number of bits, but usually 4, 8, or 16. (SC:328)

Z80: The Bally Arcade's central microprocessor. For general information about the Z80's capabilities, see Z80 Basics.

References:

• (SC) = Ciarcia, Steve, Build Your Own Z80 Computer (1981) (Google Books)