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Term
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Description
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Cable Select (CSEL)
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An optional feature of ANSI ATA specification (IDE cable connector #28). It is necessary a PC motherboard able of supporting this feature and a special IDE cable with a specially twisted pair of wire.
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Cache
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(Also known as a Buffer) An area of RAM (Random Access Memory) on the Disk Drive that temporarily stores recently accessed data, or data that is waiting to be written to the disk.
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Capacity
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The amount of data, usually expressed in bytes, which can be stored in a given device or portion of it.
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Capacity Barriers
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There are limitations on the possible data stored on disk drives due to a combination of Hardware, BIOS, and Operating System constraints. These barriers may require special installation procedures with software, or perhaps an upgrade to the hardware or to the system BIOS may be necessary in order to successfully install a drive exceeding these capacities.
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Central Processing Unit (CPU)
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The heart of the computer system that executes programmed instructions. It includes the arithmetic logic unit (ALU) for performing all math and logic operations, a control section for interpreting and executing instructions, internal memory for temporary storage of program variables and other functions.
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Channel
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A collection of electronic circuits used in the process of writing and reading information to and from magnetic media.
It is also used to indicate feautures of the transmition proccess when error correction and modulation/demodulation are concerned.
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Character
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An ordered collection of bits representing one of a set of predefined symbols. Often the term is used interchangeably with byte, but this is inexact, as a particular character may be represented by fewer or more bits that those associated with a particular byte representation.
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CHS Mode
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"Cylinder, Head and Sector" mode refers to the old standard BIOS (CMOS) setup table. It used to require the input of the number of disk drive cylinders (Cyld), heads (Hds), write pre-compensation (WPC), landing zone (LZ), and sectors per track (Sect).
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Close Loop
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A control technique that enables the positioning system to correct off-track errors in real time. The actual head position is monitored and compared to the ideal track position to determine any position error that might be occurring. This information is then used to produce a correction signal (feedback) that goes to the positioner to correct the error.
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Closed Loop Servo
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A servo control technique that uses position feedback to correct off-track errors.
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Cluster
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A group of disk sectors. The smallest allocatable unit of disk storage allowed; each FAT entry represents one cluster. Under FAT16, an average cluster is 16K; under FAT32, clusters are only 4K on partitions up to 8GB. Other logical disk formats (such as NTFS) may use different cluster size values.
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Complementary Metal Oxide Semiconductor (CMOS)
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A special type of chip. The original name for the chip that holds the system BIOS. So called because this form of Intergrated Circuit (IC) can hold the contents of it's memory with a very small current drain on a battery.
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Component Design Life
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It is defined as:
a) the time period before identified wear-out mechanisms or other system-wide factors impact the failure rate, or
b) the time period up to the wear-out point at which useful component life expires
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Controller
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1) An electronic device for connecting one or more mass storage peripherals (rigid disk drives, tape drives, and optical disk drives) to the input/output circuits of a host computer. Controllers vary in complexity, with more sophisticated units able to buffer and schedule commands, correct data errors, and bypass media defects without host intervention.
2) A miniature CPU dedicated to controlling a peripheral device, such as a disk drive, tape drive, video display terminal, or printer. The controller executes commands from the central processing unit and reissues commands to the peripheral device.
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Correctable Error
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An error that can be identified by the use of Error Detection and be overcome by using Correction schemes.
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CPI
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Flux Changes Per Inch.
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Cylinder
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Hard disk drives are usually made up of multiple platters, or disks, with one read/write head on each surface. So track 0 would be the 1st track on each platter surface. All track 0's on all platter surfaces would be Cylinder 0.
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Cylinder Zero
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The outermost cylinder in a drive that can be used for data storage.
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