Educational program - FULL DESCRIPTION + FULL ROM DISASSEMBLER TR-DOS 5.04 (5.03)

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(c) P. Fedin  @@@@

 FULL DESCRIPTION + FULL ROM DISASSEMBLER TR-DOS 5.04 (5.03)
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 FOR PROFESSIONALS, AND ALSO FOR THOSE WHO WANT TO BECOME THEM
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 continued

Address 7450. Handling syntax error. Install 23610,
23822, 23829, and all for subroutine 467. Also used withaddresses 7465 (error handling; in A - error code, in HL - address
messages).
7450 BIT 7,(IY+0); BASIC error code already assigned?
 JR Z,7461 ;if not, then installation error
      LD A,11 ;NONSENCE IN BASIC
      LD (23610),A
7461 INC A ;receiving DOS error code
      LD HL,10674 ;message address ERROR
7465 CALL 963 ;print message if possible
      JP 467 ;completion
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Address 7471.  Handling an error received from a BASIC ROM without
stack clearing. Install 23610.
7471 LD A,(23610);take the BASIC error code
 LD HL,10186 ;message address *BREAK*
      CP 20 ;BREAK INTO PROGRAM ?
      JR Z,7465 ;if yes, then print the message
      CP 12 ;BREAK - CONT REPEATS ?
      JR Z,7465 ;if yes, then print the message
      LD HL,10194 ;message address OUT OF RAM
      CP 3 ;OUT OF MEMORY ?
      JR Z,7465 ;if yes, then print the message
      LD HL,10205 ;message address ARRAY NOT FOUND
      CP 1 ;VARIABLE NOT FOUND ?
      JR Z,7465 ;if yes, then print the message
      JR 7450 ;otherwise message *ERROR*
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Address 7501. Executing the RUN command. Install 23825 and 23611.
7501 CALL 6226 ;download file
 CALL 6198 ;parameter processing and file loading
      CALL 7541 ;if there is a syntax check, then return
      LD HL,(23782); take the default file download address
 Error!! After all, the file could have been downloaded to a different address. In the sub-
program 6315 needs to store the actual address of the register in 23840
download the file, and here restore it.
 LD A,(23781) ;file extension B ?
CP "B"
      JP Z,298 ;if yes, then launch the program in BASIC
      PUSH HL ;launch the program in codes
      RET
Oh my God!! Well who does that!!! Firstly, the program address when downloaded
start must be in BC;  secondly, you need to completely quit TR-DOS,
otherwise the program will go crazy when calling 15635;  thirdly, where the program
Ramma will be coming back?;  fourthly... In general, it should be like this
(after CALL 7541):
LD A,(23781)
CP "D"
      JP Z,7450
      CP "B"
      J.P.Z.298
      LD HL,START
      LD (23834),HL
      JP 467
───────────────────────── ─────────────────── ────────────────────
START CALL 562
LD BC,(23840)
      PUSH BC
      RET
───────────────────────── ─────────────────── ────────────────────
Address 7523. Clearing the working memory area.
7523 LD HL,23822;clean the work area?
LD A,(HL)
      CP 255
      LD (HL),0 ;work area cleared
      RET NZ ;if the work area is cleared, then return
      RST 32 ;cleaning the work area
      DEFW #1bBF
      RET ;return
───────────────────────── ─────────────────── ────────────────────
Address 7536. Checking whether the string is being checked for syntax or
command execution.  If execution is in progress, the Z flag will be reset
shen, otherwise installed.
7536 BIT 7,(IY+1)
 RET
 to be continued...