Scor­pio News

The commands enabled in my system RCP are DIR, REN, TYPE and LIST (Send file to Printer). I cam also fit in PEEK, POKE, PROT, REG, REN, WHL and WHLQ.

The CP command allows file copying. It allows renaming during copying but it does not perform a Verify. I like to always verify copies, so I use a utility like MCOPY, VFILER or NSWP.

The P)eek commend will display 256 HEX and ASCII bytes from the given address, and the POKE command allows bytes to be changed using either HEX or ASCII.

PROT allows file attribute bits to be set/​reset, e.g. SYS/​DIR RO/RW.

REG allows manipulation of certain reserved memory locations that can interact with certain Z system utilities. I have not yet familiarized myself with this facility.

NOTE is the same as the optional command in the CCP.

ECHO will cause the text following the command to be sent to the screen or printer. It also allows command strings to be sent to the output device, since all characters are sent as typed.

WHLQ enables the state of the ‘Wheel Byte’ to be examined, and WHL permits it to be SET or RESET. The Wheel Byte is a system security device. Any or ALL CCP and RCP commands may be set to check the Wheel Byte before proceeding. Thus certain commands might be permitted, but others barred. On a Remote Access system, the Wheel Byte can prevent users from ‘Vandalizing’ the system. Access to other directories, drives, etc, can be barred.

If the user types an M, whilst at system level, the commands enabled in the current RCP will be displayed. Note that several of the commands provided in the RCP are also available as command files, which eases the problem of deciding which commands to include or omit from the RCP.

A description of the ZCPR3 Segments and Buffers

CP/M 2.2 can be ‘moved’ in 1k units via MOVCPM in the ordinary way. By altering a byte within MOVCPM however, moves as small as 100h bytes are possible. This is described in more detail in the installation part of this article. Thus once the decision to resite CP/M is made, at least another 256 bytes are added or removed.

If the additional software that caused the need to move CP/M down does not need all of these bytes, it is just as well to use them for something else, as to waste them. So if for example it is decided to implement the External FCB and this needs more space above CP/M, then the message buffers and shell stack become possible as well at no extra cost in memory.

External CCP Stack.

In order to ‘cram’ as many commands as possible into the CCP, the user has the option of placing the CCP stack inside or outside of the CCP memory area. This is especially important with Z2, where there ie no extension of the CCP (RCP Segment). The External Stack area occupies 30H bytes, if enabled, which is generally the case.

Multiple Command Line Buffer (MCB).

Standard CP/M allows only one command per line of input. It is possible to get around this to some extent by using extended command processing, i.e. Submit type operarion. However the occasion ofcan arisen when it would be nice to be able to type a ‘one-off’ and go away to make cuppa. The type ahead available on the Gemini keyboards helps somewhat, but seems to gobble up characters at odd times even if a judicious number of returns are typed between commands. Z2 and Z3 permit the user to enable a multiple commend line facility. This allows multiple commands to be typed, separate by a semicolon.