System information

assembler: Program that translates assembly language into the binary machine code. Assembly
language is simply a set of mnemonics used to designate the instruction set of the CPU. See
ASM in Section 3 of this manual.
back-up: Copy of a disk or file made for safekeeping, or the creation of the duplicate disk or file.
Basic Disk Operating System: See BDOS.
BDOS: Basic Disk Operating System. The BDOS module of the CP/M operating systemprovides
an interface for a user program to the operating. This interface is in the form of a set of function
calls which may be made to the BDOS through calls to location 0005H in page zero. The user
program specifies the number of the desired function in register C. User programs running under
CP/M should use BDOS functions for all I/O operations to remain compatible with other CP/M
systems and future releases. The BDOS normally resides in high memory directly below the
BIOS.
bias: Address value which when added to the origin address
of your BIOS module produces lF80H, the address of the BIOS
module in the MOVCPM image. There is also a bias value that
when added to the BOOT module origin produces 0900H, the address
of the BOOT module in the MOVCPM image. You mu'st use these
bias values with the R command under DDT or SID" when you patch
a CP/M system. If you do not, the patched system may fall to
function.
binary: Base 2 numbering system. A binary digit can have one of two values: 0 or 1. Binary
numbers are used in computers because the hardware can most easily exhibit two states: off and
on. Generally, a bit in memory represents one binary digit.
Basic Input/Output System: See BIOS.
BIOS: Basic Input/Output System. The BIOS is the only hardware-dependent module of the
CP/M system. It provides the BDOS with a set of primitive I/O operations. The BIOS is an
assembly language module usually written by the user, hardware manufacturer, or independent
software vendor, and is the key to CP/M's portability. The BIOS interfaces the CP/M system to
its hardware environment through a standardized jump table at the front of the BIOS routine and
through a set of disk parameter tables which define the disk environment. Thus, the BIOS
provides CP/M with a completely table-driven I/O system.
BIOS base: Lowest address of the BIOS module in memory, that by definition must be the first
entry point in the BIOS jump table.
bit: Switch in memory that can be set to on (1) or off (0). Bits are grouped into bytes, eight bits
to a byte, which is the smallest directly addressable unit in an Intel 8080 or Zilog Z80. By
common convention, the bits in a byte are numbered from right, 0 for the low-order bit, to left, 7
Appendix H : Glossary CP/M Operating System Manual
H-2