There are no directories, but "user areas" numbered from 0 to 15, so different users can have different files on the same disk. User areas are selected with the USER command. However, most people used user areas as poor-man's directories.

There is no COPY command. Copying files (and much more) is done with a program named PIP (peripheral interchange program). For instance,

    PIP B:=A:*.COM[E]

What was great about CP/M was that it allowed programs to run on different computers, as long as they were 8080- or Z80-based. It was a thin, but very effective abstraction layer between the hardware and a program.

MSDOS, which was originally based on CP/M, was a step back, really, because everybody tried to program the hardware directly instead of going through the proper interfaces.

But in the Turbo Pascal 3 era, the differences weren't that high.

"Big" things were:

- no sub-directories

- no relocatable executables (ie. only .COM, no .EXE)

- no common, advanced graphic standard

So if you're running WordStar or TP3 in black-and-white text mode, you might not be able to tell the difference.

If you're thinking of color text modes (TP 5.5, QBASIC, Word 5) or VGA/EGA games when "DOS" is mentioned, then that's the era beyond that.

Later versions of CP/M did add one approximation to directories, each disk contained 16 numbered user areas (0-15), you could switch between them by "USER n" command. But, all files existed in the same physical directory, the user area was just a nibble in the directory entry. Files not in the current user area were hidden.

Some versions of CP/M supported password-protecting individual files (and entire disks). If you set a password on a file/disk, the OS would prompt you for the password before allowing you to read/write it. However, there was no encryption, and the passwords were stored using trivial reversible encryption (XOR with a single byte key), so tools existed to retrieve the password.

CP/M file system did not store exact size of files, only how many 128 byte records they contained. Text files used ^Z character as end of file marker. That is why many DOS programs treated ^Z as an end of file marker, even though unlike CP/M it supported storing file sizes to the byte.

Unlike DOS, earlier versions of CP/M did not store file modification times. Later versions added this.

CP/M only supports 7-bit ASCII in file names since high bit of each file name byte is used to store file attributes (read-only, system, etc). The FAT filesystem stores file attributes in a separate byte, enabling use of 8-bit extended ASCII in filenames (diacritics for European languages, etc)

DOS tended to have friendlier commands. COPY vs PIP (Peripheral Interchange Program)

DOS copied a number of features from CP/M - 8.3 file name format, drive letters, similar system calls – Int 21h started out as a subset of CP/M system calls, but later added many more calls which were not CP/M compatible – .COM as an executable file extension, IO.SYS/MSDOS.SYS split (in CP/M called BIOS vs BDOS – the BIOS of IO.SYS is not the same thing as the system firmware BIOS.) DOS added .EXE file format and FAT filesystem. Starting in DOS 2.0, DOS gained subdirectories and a new Unix-inspired file API.

CP/M most commonly was used on 8080/Z80 systems with maximum 64KB address space, with more memory sometimes accessible through bank switching. MS-DOS ran on 8086 which is much more generous with memory. (However, there were versions of CP/M for other CPUs, including 8086 and 68000, although use of those versions was not very common.)

https://github.com/jhallen/cpm

Others have covered the DOS and CP/M comparison.