[galkk]

My English is worse than yours, but still, if anybody is curious. I'm really impressed with your documentation. I started at around 94 with Turbo Pascal and really struggled with absence of good books/reference materials and lack of English language knowledge, as I studied German in school.

    Positioning (fn42h)
    
    When pointer is moved [advanced?], take value of highest bit of CX register as special flag value. After jump? [hard to understand, the literal work is positioning], when pointer will point the code "LATRO", add or subtract from the pointer the value offset veryend [not exactly clear]. If pointer points after end of the file and MS DOS [interrupt?] is triggered decrease from DX:AX offest veryend (Elementary!)

    Reading (fn 3Fh)
    
    In case if current position < 1Ch, then, later remembering to restore current position, read necessary amount of bytes from the end of the file (eof - |offset veryend - offset save_area|) [it is not clear, but it really looks like there is modulo]. During capture of LATRO area, trim the read (SRF).
                                  ^ (curpos + numread) > (eof -offset veryend)

Let me guess. Питер Абель, Язык Ассемблера для IBM PC и программирования. ?