System information

prompt: Any characters displayed on the video screen to help the user decide what the next
appropriate action is. A system prompt is a special prompt displayed by the operating system.
The alphabetic character indicates the default drive. Some applications programs have their own
special prompts. See CP/M prompt.
PUN: Logical CP/M punch device. The punch device is an output-only device accessed through
the PUNCH entry point of the BIOS. In certain implementations, PUN: can be a serial device
such as a modem.
PUNCH: BIOS entry point to a routine that sends a character to the punch device.
RDR: Logical CP/M reader device. The reader device is an input-only device accessed through
the READER entry point in the BIOS. See PUN:.
READ: Entry point in the BIOS to a routine that reads 128 bytes from the currently selected
drive, track, and sector into the current DMA address.
READER: Entry point to a routine in the BIOS that reads the next character from the currently
assigned reader device.
Read-Only (R/O): Attribute that can be assigned to a disk file or a disk drive. When assigned to
a file, the Read-Only attribute allows you to read from that file but not write to it. When assigned
to a drive, the Read-Only attribute allows you to read any file on the disk, but prevents you from
adding a new file, erasing or changing a file, renaming a file, or writing on the disk. The STAT
command can set a file or a drive to Read-Only. Every file and drive is either Read-Only or
Read-Write. The default setting for drives and files is Read-Write, but an error in resetting the
disk or changing media automatically sets the drive to Read-Only until the error is corrected. See
also ROM.
Read-Write (R/W): Attribute that can be assigned to a disk file or a disk drive. The Read-Write
attribute allows you to read from and write to a specific Read-Write file or to any file on a disk
that is in a drive set to Read-Write. A file or drive can be set to either Read-Only or Read-Write.
record: Group of bytes in a file. A physical record consists of 128 bytes and is the basic unit of
data transfer between the operating system and the application program. A logical record might
vary in length and is used to represent a unit of information. Two 64-byte employee records can
be stored in one 128-byte physical record. Records are grouped together to form a file.
recursive procedure: Code that can call itself during execution.
reentrant procedure: Code that can be called by one process while another is already executing
it. Thus, reentrant code can be shared between different users. Reentrant procedures must not be
self-modifying; that is, they must be pure code and not contain data. The data for reentrant
procedures can be kept in a separate data area or placed on the stack.
Appendix H : Glossary CP/M Operating System Manual
H-15