You've got all the BIOS calls you need to actually shunt sectors on and off disk, read keystrokes, and display characters, right?
So with some code simple enough to hand-assemble you could write the bare bones of a Forth "inner interpreter", and from there the Forth compiler, which necessarily has a command line interpreter (or at least, a thing that breaks a text buffer down into words).
Then a simple "DOS" would have a command like "dir" which would read the directory sector into a block, format it, and print it, and so on.
Using a normal Forth-style "block editor" on a system with files wouldn't have to be complicated, you'd just be working on a 1kB (two sectors) block at a time, starting from the first block referenced by the filename.
You'd get to a point where you could read, edit, and compile Forth definitions or even just cope with text files in MS-DOS formatted disks pretty quickly.
So with some code simple enough to hand-assemble you could write the bare bones of a Forth "inner interpreter", and from there the Forth compiler, which necessarily has a command line interpreter (or at least, a thing that breaks a text buffer down into words).
Then a simple "DOS" would have a command like "dir" which would read the directory sector into a block, format it, and print it, and so on.
Using a normal Forth-style "block editor" on a system with files wouldn't have to be complicated, you'd just be working on a 1kB (two sectors) block at a time, starting from the first block referenced by the filename.
You'd get to a point where you could read, edit, and compile Forth definitions or even just cope with text files in MS-DOS formatted disks pretty quickly.