Add Support for the PO Disk Image Format

[trudnai]

File Extension (PO/*.DSK) - This image is 143360 bytes in size (143488 with MacBinary header). It usually has the *.DSK extension, but may also be found with the *.PO extension as well. This disk-image stores data in block rather than track/sector format (block 0, block 1 -> block 279) - the difference in the structure is due to ProDOS interleaving data in blocks (which equal two DOS sectors). Although newer emulators are capable of distinguishing between DO and PO (and thus using both) older emulators strictly require the DO type despite the identical size. ProDOS Order images are still useful since they are capable of being converted back into SDK images by "Nulib" (which are compatible with ShrinkIt on the Apple). DO images are not capable of this. PO is an older disk-image format (used more widely with Unix emulators, since ShrinkIt archives extracted by "Nulib" produce PO images). Like DO, this format is incapable of storing copy- protected software unless it has been "cracked" first. A basic guide to determining what type is software may be stored in a PO image is whether it can be first duplicated on an Apple with standard copy utilities such as "copya".
On the MACINTOSH - The file must be downloaded in binary mode. None of the Macintosh emulators really use the PO format, except for "][ In a Mac", which uses images of non-standard size. To use this format with "][ In a Mac", drop a DO or Copy II+ 7.1 image file onto "Image Converter" by Lazarus I. Long and select the required format; output images will have the correct resource information. The application "Easy Convert" will re-order the sectors of a PO disk-image into DOS3.3 Order, and will automatically set the file type/creator attributes upon output to 'DSK5'/'A2EM' for use with STM. Alternatively, use "ProDOS-Order Converter".
PROGRAM LOCATIONS:
ftp://ftp.apple.asimov.net/pub/apple_II/utility/ic.sit
ftp://cassandra.ucr.edu/pub/apple2/easy.convert.1.0.sea.hqx
ftp://ftp.apple.asimov.net/pub/apple_II/utility/Po_to_Do.gz
ftp://ftp.apple.asimov.net/pub/apple_II/utility/ProDOSOrderConv.sit.bin
On the PC - No emulators on the PC require PO images (although newer emulators such as AppleWin support them). Use "Mapper" by Rene Gaudet reneg@cpqhou.compaq.com to convert DO to PO and vice versa.
PROGRAM LOCATIONS:
ftp://ftp.apple.asimov.net/pub/apple_II/utility/mapper.zip