In computer terminology, a cylinder refers to a series of tracks on a direct access storage device, or DASD, that are the same distance from the disk's axis of rotation.

DASD, or hard disks, are typically composed of several platters, which spin at a high rate. A band of adjacent magnetized spots on the platter is a track. A series of tracks on different platters that occupy the same radius are a cylinder.

Data written to the tracks within a cylinder may be accessed more quickly than data that lies outside the cylinder, because once the disk device's arm is positioned to read one track, every other track within the cylinder can be read without repositioning the arm. Such arm movements, known as seek actions, are among the most costly I/O operations in terms of time.

Cyl"in*der (s?l"?n-d?r), n. [F. cylindre, OF. cilindre, L. cylindrus, fr. Gr. , fr. ,, to roll. Cf. Calender the machine.]

1. Geom. (a)

A solid body which may be generated by the rotation of a parallelogram round one its sides; or a body of rollerlike form, of which the longitudinal section is oblong, and the cross section is circular.


The space inclosed by any cylindrical surface. The space may be limited or unlimited in length.


Any hollow body of cylindrical form

, as: (a)

The chamber of a steam engine in which the piston is moved by the force of steam.


The barrel of an air or other pump.

(c) Print.

The revolving platen or bed which produces the impression or carries the type in a cylinder press.


The bore of a gun; the turning chambered breech of a revolver.


The revolving square prism carryng the cards in a Jacquard loom.

Cylinder axis. Anat. SeeAxis cylinder, under Axis. -- Cylinder engine Paper Making, a machine in which a cylinder takes up the pulp and delivers it in a continuous sheet to the dryers. -- Cylinder escapement. See Escapement. -- Cylinder glass. See Glass. -- Cylinder mill. See Roller mill. -- Cylinder press. See Press.


© Webster 1913.

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