DOS 3.3 and ProDOS use different orderings. It is common to use .do or .po as a file extension to be explicit about the filing system ordering. What a DOS file assumes isn’t standardised. Scavenging the histories leads to parameters and formats that are deprecated or superseded.
There are several Apple II disk image formats and tools. .dsk files are usually DOS 3.3 or ProDOS format. Typically .do is DOS 3.3, often 16 sectors but sometimes 13. .po is ProDOS format. Hard drive images use .hdv in ProDOS order. Disk images archive and maintain files.
DOS 3.3 files have a third byte indicating file type. Bit 7 shows if the file is locked. Some types like R files were for few applications. Although S, A and B types were included, no use was defined.
Putting files onto images can need conversions to disk format. Cpmtools utilities transfer CP/M programs directly. ShrinkIt utilities handle most Apple II images, but not all unshrinking works.
DOS 3.3 automatically tracks files and space. It came with early Apple II Disk II drives. Programs written for 3.2.1 needed conversion to work with 3.3. The Apple Pascal DOS was more limited.
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