Information Technology Reference
In-Depth Information
head is appropriately positioned, reading and writing of the file can
occur by allowing the disk to rotate. Such processing can be partic
ularly smooth and efficient.
When a disk is highly fragmented, therefore, one might want to
reorganize where material is stored on the disk to obtain a contigu
ous arrangement of file sections. Such a process is called
defrag-
menting a disk
, and this task typically can be performed by various
utility programs. It should be noted that the defragmenting process
can take considerable time for a highly fragmented disk for at least
two reasons:
1.
Modern disks have large capacities, with the ability to store
many files and a large number of tracks and sectors. Thus, de
fragmentation may require the analysis and movement of
large amounts of data.
2.
When moving sectors of one file together, some pieces of
other files may have to be moved out of the way first.
Overall, data may have to be moved several times before a fi
nal, satisfactory arrangement is found.
Complete disk defragmentation may consume a lot of time if a
disk has become highly fragmented or disorganized. The amount of
time needed to complete the defragmentation may even range up to
several hours, so this is a process that some folks prefer to run
overnight, when the machine is not being used for other purposes.
After the deframenting work is completed, disk access can proceed
relatively efficiently, sometimes making a noticeable difference in
performance.
A
computer virus
is an unwanted or unanticipated program, of
ten designed to damage a computer or degrade its performance. A
relatively benign virus might pop up a window on a computer
screen, displaying a surprise message. More destructive viruses might
erase files, change data, send many email messages, or degrade com
puter performance (perhaps by consuming much CPU time).
Viruses are programs, so they perform their work when the CPU
runs them. Because a virus does unwanted work, a user would be
