System information

CP/M 1.4 compatiblity should be aware of the implications of this difference. See CP/M 1.4
compatibility.
extent mask (EXM): A byte parameter in the disk parameter block located at DPB + 3. The
value of EXM is determined by the block size (BLS) and whether the maximum data block
number (DSM) exceeds 255. There are EXM + 1 extents per directory FCB.
FCB: See File Control Block.
file: Collection of characters, instructions, or data that can be referenced by a unique identifier.
Files are usually stored on various types of media, such as disk, or magnetic tape. A CP/M file is
identified by a file specification and resides on disk as a collection of from zero to 65,536
records. Each record is 128 bytes and can contain either binary or ASCII data. Binary files
contain bytes of data that can vary in value from 0H to 0FFH. ASCII files contain sequences of
character codes delineated by a carriage return and line-feed combination; normally byte values
range from 0H to 7FH. The directory maps the file as a series of physical blocks. Although files
are defined as a sequence of consecutive logical records, these records can not reside in
consecutive sectors on the disk. See also block, directory, extent, record, and sector.
File Control Block (FCB): Structure used for accessing files on disk. Contains the drive,
filename, filetype, and other information describing a file to be accessed or created on the disk. A
file control block consists of 36 consecutive bytes specified by the user for file I/O functions.
FCB can also refer to a directory element in the directory portion of the allocated disk space.
These contain the same first 32 bytes of the FCB, but lack the current record and random record
number bytes.
filename: Name assigned to a file. A filename can include a primary filename of one to eight
characters; a filetype of zero to three characters. A period separates the primary filename from
the filetype.
file specification: Unique file identifier. A complete CP/M file specification includes a disk
drive specification followed by a colon, d:, a primary filename of one to eight characters, a
period, and a filetype of zero to three characters. For example, b:example.tex is a complete
CP/M file specification.
filetype: Extension to a filename. A filetype can be from zero to three characters and must be
separated from the primary filename by a period. A filetype can tell something about the file.
Some programs require that files to be processed have specific filetypes.
floppy disk: Flexible magnetic disk used to store information. Floppy disks come in 5 1/4- and
8-inch diameters.
FSC: Parameter in the diskdef macro library specifying the first physical sector number. This
parameter is used to determine SPT and build XLT.
Appendix H : Glossary CP/M Operating System Manual
H-10