System information

BTREE: General purpose file access method that has become the standard organization for
indexes in large data base systems. BTREE provides near optimum performance over the full
range of file operations, such as insertion, deletion, search, and search next.
buffer: Area of memory that temporarily stores data during the transfer of information.
built-in commands: Commands that permanently reside in memory. They respond quickly
because they are not accessed from a disk.
byte: Unit of memory or disk storage containing eight bits. A byte can represent a binary
number between 0 and 255, and is the smallest unit of memory that can be addressed directly in
8-bit CPUs such as the Intel 8080 or Zilog Z80.
CCP: Console Command Processor. The CCP is a module of the CP/M operating system. It is
loaded directly below the BDOS module and interprets and executes commands typed by the
console user. Usually these commands are programs that the CCP loads and calls. Upon
completion, a command program may return control to the CCP if it has not overwritten it. If it
has, the program can reload the CCP into memory by a warm boot operation initiated by either a
jump to zero, BDOS system reset (Function 0), or a cold boot. Except for its location in high
memory, the CCP works like any other standard CP/M program; that is, it makes only BDOS
function calls for its I/O operations.
CCP base: Lowest address of the CCP module in memory. This term sometimes refers to the
base of the CP/M system in memory, as the CCP is normally the lowest CP/M module in high
memory.
checksum vector (CSV): Contiguous data area in the BIOS, with one byte for each directory
sector to be checked, that is, CKS bytes. See CKS. A checksum vector is initialized and
maintained for each logged-in drive. Each directory access by the system results in a checksum
calculation that is compared with the one in the checksum vector. If there is a discrepancy, the
drive is set to Read-Only status. This feature prevents the user from inadvertently switching disks
without logging in the new disk. If the new disk is not logged-in, it is treated the same as the old
one, and data on it might be destroyed if writing is done.
CKS: Number of directory records to be checked summed on directory accesses. This is a
parameter in the disk parameter block located in the BIOS. If the value of CKS is zero, then no
directory records are checked. CKS is also a parameter in the diskdef macro library, where it is
the actual number of directory elements to be checked rather than the number of directory
records.
cold boot: See boot. Cold boot also refers to a jump to the boot entry. point in the BIOS jump
table.
COM: Filetype for a CP/M command file. See command file.
Appendix H : Glossary CP/M Operating System Manual
H-4