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ac2f10996a
Trying to make sense out of the disk image creation process so that it is easier to maintain going forward. This is just the initial round of changes.
30 lines
2.0 KiB
Plaintext
30 lines
2.0 KiB
Plaintext
To: ZDE 1.6 Users
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From: Carson Wilson
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Date: 12 Nov 90
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About: Fix for control character display problems.
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Lee Rimar noticed that ZDE version 1.6 would not display control characters
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correctly on his equipment. Embedded control codes in his files such as
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control-S or control-Y were highlighted, but the characters didn't always
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correspond to those in his files.
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When Lee's friend Roger Bond discovered that the bug did not appear under
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ZSDOS, I was able to track down and eliminate the problem. As Roger Bond
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suspected, the bug is due to the differences between ZSDOS and standard
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CP/M. Apparently his "vanilla" CP/M software was using the AF' register.
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There is a long-standing controversy on this issue, but the ZSDOS team
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elected to play it safe and leave the "alternate registers" intact. In
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upgrading ZDE, I made the (mistaken) assumption that the AF' register would
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reliably store the value to be output in alternate video, and since many
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machines DO preserve AF', the mistake didn't show up on them.
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The next version of ZDE will fix the problem, but if you find that control
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characters are not displaying correctly on your computer you can also make
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the following changes to ZDE (version 1.6 ONLY) with DDT.COM or a patcher
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like Steve Cohen's ZPATCH:
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Address (100h offset) Old Value (opcode) New Value (opcode)
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--------------------- ------------------ ------------------
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389C hex 08 hex (ex af,af') F5 hex (push af)
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38A0 hex 08 hex (ex af,af') F1 hex (pop af)
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