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Glossary
IBM System Storage DCS9550 1S1 Storage Expansion Unit Installation, Service, and User Guide 53
Glossary
In glossary definitions, italics are used for items defined elsewhere in the glossary and bold is used for
the items shown in brackets after the main heading of the entry.
ASCII American Standard Code for Information Interchange. A 7-bit binary code (0's, 1's) used to
represent letters, numbers, and special characters such as $,!, and /. Supported by almost every
computer and terminal manufacturer.
ATA (Advance Technology Attachment) A disk drive interface standard based on a 16-bit bus and
dealing with the power and data signal interfaces between the motherboard and the integrated disk
controller and drive. The ATA "bus" only supports two devices - master and slave.
Attribute Setting that controls access to a specific file. Often used to protect important files (such as
the Registry files) from accidental change or deletion. Set using the ATTRIB command in MS-DOS.
Backplane A printed circuit board incorporated in the chassis assembly to provide logic level signal, and
low voltage power distribution paths.
Bay The slot that a unit or media device fits into.
Byte A group of binary digits stored and operated upon as a unit. A byte may have a coded value equal
to a character in the ASCII code (letters, numbers), or have some other value meaningful to the computer.
In user documentation, the term usually refers to 8-bit units or characters.
1 kilobyte (K) is equal to 1,024 bytes or characters; 64K indicates 65,536 bytes or characters.
Cable Throughout this DCS9550 1S1 Storage Expansion Unit user guide this term is used in
accordance with the preferred US context of: “an insulated flexible electric wire used for the transmission
of data signals between computer equipment.”
Note: Cable is UK preferred terminology for either a power cord or a data cable:
Character A representation, coded in binary digits, of a letter, number, or other symbol.
Characters Per Second A data transfer rate generally estimated from the bit rate and the character
length. For example, at 2400 bps, 8-bit characters with Start and Stop bits (for a total of ten bits per
character) will be transmitted at a rate of approximately 240 characters per second (cps).
Chassis A sheet metal enclosure incorporating a Backplane PCB, an integral Ops Panel.and a module
runner system. The chassis contains a number of 'Bays', each of which can accommodate a plug in
module. There are sixteen drive carrier bays at the front and five bays at the rear which house power
supply/cooling and SCM I/O modules.
Configure To set up a hardware device and its accompanying software.
Data Communications A type of communications in which computers and terminals are able to
exchange data over an electronic medium.
Disk (drive, carrier, module) A SATA disk drive mounted in a carrier. You can have up to sixteen disk
drive carrier modules in each DCS9550 1S1 Storage Expansion Unit.