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The buffer is (normally) 200 bytes long. Commands like:

A0>M80 =BIOS;ECHO Linking;L80 BIOS/N,BIOS//E;ECHO Erasing;ERA *.BAK

then become possible which is very useful to the user. The MCB is in fact widely utilized by the Z system utilities for maximum power and flexibility. If a commend string is found in this buffer on cold boot, the command(s) will be executed. Unless the multiple command facility is enabled, the Z system cannot function to any real advantage.

Memory Based Named Directory Segment.

As intimated above, I feel that this facility is not of any especial advantage on a single user system based on a couple of smallish floppies. On a system with several users, especially where a Winchester is used, the situation is completely different. If this facility is enabled, up to 14 (Could be extended at cost of more memory) Names may be allocated to Drives and USER areas. Thus A16: contains HLP files. A15: contains most system utilities, etc. Typical name allocations are:

A16 –– HELP,       A15 –– ROOT,       A0 –– BASE,       C0 –– BAK,       P0 –– MDSK

The names allocated are a matter of user preference. I keep Z3 System development files in B0, so this I call Z3, and BASIC in A4: so this is called BAS. The main benefit of this is that one does not have to remember which DU one has allocated to a certain function. The directory name is displayed in the prompt:

A0:BASE>       C0:BAK>       B6:PAS>       P0:MDSK> etc;

To move about one may use either the DU: or DIR: form and so–

In addition Z system utilities recognize either DU: or DIR: form so–

are ALL equally valid. Directory names may be up to 8 characters long, and may optionally be password protected by a password of up to 8 characters long. For more security, the DU: form of access may be disabled, so that password protected directories become more secure, especially to non technical user. Wheel protection of Disabling of the ‘Peek’ command, and removal of debug utilities would be strictly necessary to give added protection where more experienced users were using the system. A moderately secure system is possible however, in a multi user environment.

One particular point about allowing DIR names and USER areas to be displayed in the CCP prompts is that the screen edit feature of most of our BIOS’s needs to be modified. This Feature starts by looking for the ‘>’ prompt in the EDIT line returned from the Screen, and in both SYS and MAP BIOS’s starts at about the 4th character out from the start of the line. I have modified this to start out at about the 12th character as the extra data before the ‘>’ can move this prompt character well out into the line. If the BIOS source is available this can be easily changed, otherwise it becomes a question of asking the supplier to tell you which byte changes the start point of this routine, or doing a bit of work with a debugger or disassembler. Generally no extra code is needed, (in fact I rewrote the routine in my BIOS and saved a number of bytes). – just a change of address to point further into the edit buffer and increase the loop counter. e.g. the original code in SYS18 was LD HL,EDBUF+3, LD B,3 and I changed this to LD HL,EDBUF+12, LD B,12. EDBUF a a block of about 83 – 00 characters in a system image, and the code to be modified usually lies just before this buffer.