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
|BYTES >||01||04||4A||4F||48||4E||20 20 20 20||58||45||47||48||20 20 20 20|
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
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