Scor­pio News

are all legal and acceptable. ( Extra spaces for clarity )

The author of the Z system, recognising that this freedom destroys any security between different users, has provided several security systems. These include the ‘Wheel Byte’, which can be set to deny users access to selected system commands. This can also stop non authorised users for example, from using the system ‘P’ (Peek) command, to read system passwords. It can also be used to prevent remote access users from ‘vandalising’ the system. The system operator or anyone with sufficient knowledge of the system can set the wheel byte to allow himself access.

The system also allows a limit to be set to the maximum user number that can be accessed, By loading a different system overlay, the system operator can allow himself access to higher user numbers, where ‘sensitive’ files like Disk Editors, Debuggers and System files may be kept. Programs like these could of course be used to read passwords from system files, disk tracks, or RAM.

The main security measure provided in ZCPR3 is to ‘Password’ protect certain directories. In the Z system directories are based on simple Disk/​User structures, rather than on any elaborate ‘tree’ structure. Depending on the amount of RAM one is prepared to allocate to named directories, 14 names are available for each 256 bytes of RAM. In practice, 14 names seem adequate. The system operator needs only decide which DU is to be allocated to a function or operator, and to name the DU. Thus if an operator is to be allocated the ‘DIR’ JOHN: on User 4 of drive A, then when the system operator makes up the named directory, the relevant entry will be:

The name may be up to 8 characters in length, but this would only make for more typing, and up to 4 characters is usually adequate. The second block of 8 bytes may be left as spaces, or any ASCII code may be entered, which will be used as the password for access to that directory. In this example the password XEGH has been allocated.

When JOHN wishes to access his directory, he types JOHN: and presses enter. Since there is a password, he will be asked to type it in. If he makes a mistake, he is given one more try, after which the system defaults to the current DU.

If the relevant ZCPR3 was assembled to only allow DIR: type access, then all would be well, since attempts to access by typing A4: would fail. Limiting the system to allow only DIR: access reduces flexibility however since access to unnamed DU’s: is frequently very useful. Unfortunately if Z3 is assembled to accept DU and DIR