Hardware Reference
In-Depth Information
Expanded memory manager
An expanded memory manager (such as
EMM386.EXE included with MS-DOS 5.0 and later) provides a means of
establishing and controlling the use of expanded memory (i.e. memory above
the DOS 1 MB limit). Unlike DOS and Windows 3.1, Windows 9x incorp-
orates its own memory management and thus EMM386 (or its equivalent) is
not required. See also
Expanded memory
.
Extended memory (XMS memory)
Memory beyond the 1 MB range ordi-
narily recognized by MS-DOS. The XMS memory specification resulted from
collaboration between Lotus, Intel, and Microsoft (sometimes known as LIM
specification).
File
Information (which may comprise ASCII encoded text, binary coded
data, and executable programs) stored on a floppy disk, hard disk, or other disk-
oriented storage device (such as a solid-state USB drive). Files may be redirected
from one logical device to another using appropriate DOS commands.
File allocation table (FAT)
The file allocation table (or 'FAT') provides a
means of keeping track of the physical location of files stored on a floppy disk
or hard disk. Part of the function of DOS is to keep the FAT up to date whenever
a file operation is carried out. DOS does not necessarily store files in physically
contiguous clusters on a disk and it is the FAT that maintains the addresses of
clusters occupied by a particular file. These clusters may, in fact, be scattered
all over the surface of the disk (in which case we describe the file as having
been 'fragmented').
File attributes
Information which indicates the status of a file (e.g. hidden,
read-only, system, etc.).
Filter
In a software context, a filter is a software routine which removes or
modifies certain data items (or data items within a defined range). In a hardware
context, a filter is an electrical circuit which modifies the frequency distribution
of a signal. Filters are often categorized as low-pass, high-pass, band-pass, or
band-stop depending upon the shape of their frequency response characteristic.
Firmware
A
program
(software)
stored
in
read-only
memory
(ROM).
Firmware provides non-volatile storage of programs.
Fixed disk
A disk which cannot be removed from its housing. Note that,
whilst the terms 'hard' and 'fixed' are often used interchangeably, some forms
of hard disk are exchangeable.
Font
A set of characters (letters, numbers, and punctuation) with a particular
style and size.
Format
The process in which a magnetic disk is initialized so that it can
accept data. The process involves writing a magnetic pattern of tracks and
sectors to a blank (uninitialized) disk. A disk containing data can be reformat-
ted, in which case all data stored on the disk will be lost. An MS-DOS utility
program (FORMAT.COM) is supplied in order to carry out the formatting of
floppy and hard disks. Note that, in the case of hard drives, there are differ-
ences between the logical organization of tracks and sectors and the underlying
physical arrangement of the data stored on the drive.
