Diskette Addressing And Layout; Track And Cylinder - IBM 5110 User Manual

DISKETTE ADDRESSING AND LAYOUT
A diskette address consists of a combination of cylinder number, head
number, and record number as follows:
CC H RR
L
Record (sector) Number. The sector into which the data
is to be written or from which the data is to be read.
Head Number. The side of the diskette on'which the data is to
be written or from which it is to be read. This number is hex 0
for all one-sided diskettes and for side 0 of two-sided diskettes.
The number is hex 1 for side 1 of two-sided diskettes.
L-------Cylinder Number. This number identifies the cylinder onto which a
physical record is written or from which it is read.
Track and Cylinder
A track is the recording area on a sing.le diskette that passes the
read/write head while the disk makes a complete revolution. The
read/write head is held by a carriage that can be moved to 77 distinct
locations along a straight line from the center of the disk. Therefore,
each diskette has 77 concentric tracks on which data can be stored.
01 ",
I
I ... -. \
I
/0\ \
~
I
I
77 Tracks
\ , I I
t
\ . . . . . ", t
\'",JI-'~~-",-/-/~I-----~
The diskette drive for two-sided diskettes has a read/write head on
each side. Each track on side 0 of a two-sided diskette has an
associated track on side 1.
A cylinder is one track on a one-sided diskette or a pair of associated
tracks (the corresponding tracks on opposite sides of the diskette) on
a two-sided diskette. There are 77 cylinders (numbered 0 to 76) on a
diskette.
Diskette Concepts 83