Glossary of Terms

Term

Definition

Address

A 12 bit number assigned to a read-only-memory or
program random-access memory location corresponding
to its sequential position.

Bit

The smallest unit of information which can be represented.
(A bit may be in one of two states, 0 or 1).

Byte

A group of 8 contiguous bits occupying a single memory location.

Character

A group of 4 contiguous bits of data.

Instruction

The smallest single operation that the computer can be
directed to execute.

Object Program

A program which can be loaded directly into the computer’s
memory and which requires no alteration before execution.
An object program was usually on paper tape, and is produced
by assembling a source program, however the Pyntel4004 Assembler
can produce object code to be loaded into an emulator or directly
on to a board simulating an MCS-4.
Instructions are represented by binary machine code in an
object program.

Program

A sequence of instructions which are taken as a group to
allow the computer to accomplish a desired task.

Source Program

A program which is readable by a programmer but which must be
transformed into object program format before it can be loaded
into the computer and executed.
Instructions in an assembly language source program are represented
by their assembly language mnemonic.

System Program

A program written to help in the process of creating user programs.

User Program

A program written by the user to make the computer
perform any desired task.

nnnb

nnn represents a number in binary format.

0xnn

nnn represents a number in hexadecimal format.

Note

All numbers in this document are assumed to be decimal unless otherwise specified.

Note

../../_images/byte.png

A representation of a byte in memory.
Bits which are fixed are indicated by 0 or 1; bits vvhich may be either 0 or 1 in different circumstances are represented by letters; thus RP represents a three-bit field which contains one of the eight possible combinations of zeroes and ones.