B&R Industries Automation PC 620, User Manual

Page: 479 / 512

Appendix A • Glossary
Appen
dix
A
479 Automation PC 620 User's Manual V 1.90
(pixel) containing liquid crystals can be switched on using electrode gates, thus coloring this pixel
black. Some LCD displays have an electroluminescent plate behind the LCD screen for lighting.
Other types of LCD displays can use color.
LED
An abbreviation for »Light Emitting Diode« A semiconductor diode which converts electrical
energy into light. LEDs work on the principle of electroluminescence. They are highly efficient
because they do not produce much heat in spite of the amount of light they emit. For example,
"operational status indicators" on floppy disk drives are LEDs.
LPT
Logical device name for line printers. In MS DOS, names are reserved for up to three parallel
printer ports with the names LPT1, LPT2 and LPT3. The first parallel port (LPT1) is usually
identical to the primary parallel output device PRN (in MS-DOS the logical device name for the
printer). The lettering LPT was originally stood for "Line Printer Terminal".
MB
Megabyte (1 MB = 220 or 1,048,576 bytes)
Microprocessor
Highly integrated circuit with the functionality of a CPU, normally housed on a single chip. It
comprises a control unit, arithmetic and logic unit, several registers and a link system for
connecting memory and peripheral components. The main performance features are the internal
and external data bus and address bus widths, the command set and the clock frequency.
Additionally, a choice can be made between CISC and RISC processors. The first commercially
available worldwide microprocessor was the Intel 4004. It came on the market in 1971.
MIPS
Million Instructions Per Second > Measurement for the computing speed of computers.
Motherboard
A circuit board, which houses the main components of a computer such as the CPU switching
circuit, co-processors, RAM, ROM for firmware, interface circuits and expansion slots for
hardware expansions.
MTBF
An abbreviation for »Mean Time Between Failure« The average time which passes before a
hardware component fails and repair is needed. This time is usually expressed in thousands or
ten thousands of hours, sometimes known as power-on hours (POH).
M