CP/M Cookbook - User Areas

CP/M 2.2 does not support disk directories, all files are placed in the root directory of the disk. With a hard disk, or even a high capacity floppy disk, this would be unmanageable, but for CP/M systems such as the Memotech FDX//SDX, with small capacity floppy disks, this is not too much of a problem. Details for the common Memotech CP/M floppy disk formats are shown in the table below :

CP/M 2.2 has 16 "user areas", numbered 0 to 15, which allows files to be segregated into different logical areas on the disk. The default user area is "0", but the user can change to another area by entering the "USER x" command, where "x" is one of the available user areas. Once logged in to the new user area, the user only has access to files for that user area, although there is no security to prevent the user from selecting any user area that he wants.

User areas provide some degree of ability to organise the files on disk, and become increasingly useful as capacity increases with devices such as legacy Memotech Silicon disks, or SD cards used in Andy Key's REMEMOrizer etc.

Once logged into the new user area, there is likely to be a need to copy files between different user areas. In CP/M files are copied using the "PIP" program, but when first logged onto a new user area, PIP.COM is not visible to the user and needs to be created in that user area. This can be done by first loading PIP.COM into memory while in user area 0, changing to the new user area and writing out the block of memory still containing PIP.COM into a new file :