Scor­pio News

forms, then anyone typing A4: would succeed in entering JOHN:, since Z3 does not check to see if there is a password associated with a DU before granting access.

The modified code listed in Appendix ‘A’ will cause the Z3 CCP to check DU forms as well as DIR forms for password protection. Space is a problem in the Z3 CCP. Not all routines in the CCP are available in the RCP segment, and some perform slightly differently. In order to get the modified code into the CCP, I had to reduce the number of CCP commands to just ERA, GET and SAVE. The ZCPR3 RCP however has room to give me all of the remaining commands that I need.

The ZCPR3 source code is written in 8080 mnemonics. Some Z80 specific code is used in the CCP segment, but this is generated by the use of Macros. It is possible to save a useful number of bytes in this code by adopting more standard Z80 operations, This task is made easier if the source is translated to Z80 with a program like XLATE3.COM. I have found some dozen extra bytes without really trying too hard, and there are probably more that could be saved.

By modifying the ZCPR3.ASM file as described and re-assembling, then the Z3 CCP will check both DU: and DIR: forms of address for passwords before granting access.

Using the SVC Alternative Screen as a Command List

Some time ago I described in 80-BUS News how I had modified my BIOS so that a lead in key (^T) provided access to a number of single key operations, From relatively simple beginnings, this direct command feature grew into an extremely useful tool. For example a ^P would page the Printer and BIOS, ^S would toggle the screen paging, ^D would do a screen dump, and several keys would alter lines per page, skip-over, change the printer type, etc. In more recent versions, it was possible to strike ^F as the second key, and this would switch SVC screens. This appeared to me to be an attractive operation, but subsequently I never found much use for it.

In the version described in a previous 80-BUS News, when ^T was hit, a prompt line appeared on the top line of the screen, reminding the user of the option keys available. The main problem with this was to remember which key did what operation since they were not all functionally related and there was not enough space on the top line to display the detail needed.

Recently, whilst setting up a Z3 startup menu, it occurred to me that it would be extremely useful if entry of a ^T key switched to screen 2 of the SVC, on which could be displayed a full list of the second key options then available. After the