Hardware Reference
In-Depth Information
Joystick
A device used for positioning a cursor, pointer, or output device
using switches or potentiometers which respond to displacement of the stick in
the X and Y directions.
Jumper
Jumpers, like DIP switches, provide a means of selecting configur-
ation options on adapter cards (see
DIP switch
).
Keyboard buffer
A small area in memory which provides temporary storage
for keystrokes. See
Buffer
.
Kilobyte (KB)
1024 bytes (note that 2
10
= 1024).
Logical device
A device which is normally associated with microcomputer
I/O, such as the console (which comprises keyboard and display) and printer.
Low state
The more negative of the two voltage levels used to represent the
binary logic states. A low state (logic 0) is generally represented by a voltage
in the range 0-0.8 V.
Megabyte (MB)
1 048 576 bytes (note that 2
20
=
1 048 576). The basic
addressing range of the 8086 processor (which has 20 address bus lines) is 1 MB.
Memory
That part of a microcomputer system into which information can
be placed and later retrieved. Storage and memory are interchangeable terms.
Memory can take various forms including semiconductor (RAM and ROM),
magnetic (floppy and hard disks), and optical disks. Note that memory may also
be categorized as read-only (in which case data cannot subsequently be written
to the memory) or read/write (in which case data can both be read from and
written to the memory).
Memory resident program
See
TSR
.
Microprocessor
A central processing unit fabricated on a single chip.
MIDI
The MIDI (or 'Musical Instrument Digital Interface') is the current
industry standard for connecting musical instruments to a PC.
Modem
A contraction of modulator-demodulator; a communications inter-
face
device
that
enables
a
serial
port
to
be
interfaced
to
a
conventional
voice-frequency telephone line.
Modified frequency modulation (MFM)
A method of data encoding
employed with hard disk storage. This method of data storage is 'self-clocking'.
Motherboard
The motherboard (or system board) is the mother printed cir-
cuit board which provides the basic functionality of the microcomputer system
including processor (or CPU), RAM, and ROM. The system board is fitted
with connectors which permit the installation of one, or more, option cards
(e.g. graphics adapters, disk controllers, etc.).
Multimedia
A combination of various media technologies including sound,
video, graphics, and animation.
Multitasking
A process in which several programs are running simultaneously.
NAND
Inverse of the logical AND function.
Negative acknowledge (NAK)
A signal used in serial data communications
which indicates that erroneous data has been received.
