Extracting CDOS and CP/M) files

On 11 Oct 2007 at 13:05, Fred Cisin wrote: In theory, that's what the feature of the CP/M directory checksum was supposed to avoid ("DISK R/O" error). But I don't know if CDOS implemented it--and, in any case, the hole was big enough that you could drive a Peterbilt through it. Earlier versions of MS-DOS also suffered with this problem on 360K drives with no "Disk Changed" line. At Durango, we also had the problem. It was fixed it by keeping a "Files Open" flag for each drive (maintained by the filesystem). Every 2 seconds or so, each drive's "Write Protected" status was polled (didn't require turning the drive motor on or loading the heads, so it was fast). If it changed and there were files open, an audible alarm was sounded and a message saying in essence "Put that floppy back, idiot!" was displayed until the disk was again inserted. The one we never could figure a way around was the customer turning the power off before an application could terminate and close any open files, update indices, etc. The problem is still with us today. Nihil sub sole novum. Cheers, Chuck