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                                  XTAIL.COM                                   

             Size (recs) CRC   Version    Author/Latest Issue      Disk
               2k (12)   2B70  1.1        Gene Pizzetta 1/91       Z3COM27

  1- Syntax  2- Display  3- Notes                                             

   XTAIL is  a ZCPR3 utility that  displays the  command tail as parsed by the
command processor.   Both  the  default and alternate (secondary) file control
blocks are displayed as  a  hexadecimal dump and in ASCII,  as is the complete
tail in the default DMA buffer.  This program can be useful for anyone explor-
ing programming in the ZCPR3 environment.  

   Vs. 1.0 (12/21/87) by Gene Pizzetta.
:1

    Syntax   XTAIL {whatever you want}

No command line parameters or options affect the operation of XTAIL.

The distribution includes  a type-3  version  that loads at 8000h and a type-4
version that loads as high in memory as possible.  There are some slight diff-
erences in the command line buffer contents from one version to the other.
:2
 Display - 1/4 

   If it is available in your TCAP,  highlighting  will be used in the display
to make it more readable.  A typical command line and display follows:

C0:ASM>>xtail d3:myfile.txt a15:yourfile.doc /abcd

XTAIL   Version 1.1   (loaded at 0100h)
Default and alternate file control blocks:
  addr  dr filename -- -- -- -- -- filetype    us    fl
  005C: 04 4D 59 46 49 4C 45 20 20 54 58 54 00 03 00 00   |.MYFILE  TXT....|
  006C: 01 59 4F 55 52 46 49 4C 45 44 4F 43 00 0F 00 00   |.YOURFILEDOC....|
 offset: 0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15
Command tail:
  addr  ct tail  -- -- -- -- -- -- -- -- -- -- -- -- --
  0080: 25 20 44 33 3A 4D 59 46 49 4C 45 2E 54 58 54 20   |% D3:MYFILE.TXT |
  0090: 41 31 35 3A 59 4F 55 52 46 49 4C 45 2E 44 4F 43   |A15:YOURFILE.DOC|
  00A0: 20 2F 41 42 43 44 00 19 EB 0E 09 C3 05 00 4E 6F   | /ABCD........No|
C0:ASM>>
 Display - 2/4 

The header above the two file control blocks identifies important bytes:
     addr      address of file control block
     dr        drive byte (0=default, 1=A, 2=B, etc.)
     filename  name of the file
     filetype  file name extension
     us        user area byte (0=user 0, 1F=user 31)
     fl        validity flag set by some CPR's if the filespec 
               includes an invalid DU or DIR specification (the 
               drive, user, or directory does not exist) as shown 
               in the example below

The header above the command tail is simpler:
     addr      beginning address of bytes displayed
     ct        count of characters in the command tail (excluding 
               the final null byte)
     tail      the command tail itself (only enough lines are 
               displayed to show the entire tail, not the entire 
               buffer)
 Display - 3/3 

   If an invalid DU or DIR specification is given,  the CPR sets the drive and
user bytes to the current default and,  in some cases,  sets the validity flag
byte to FFh.   Normally this flag byte is zero.   For example,  entering drive
"Q" instead of "D" gives the following results:

C0:ASM>>xtail q3:myfile.txt a15:yourfile.doc /abcd

XTAIL   Version 1.1   (loaded at 0100h)
Default and alternate file control blocks:
  addr  dr filename -- -- -- -- -- filetype    us    fl
  005C: 03 4D 59 46 49 4C 45 20 20 54 58 54 00 00 00 FF   |.MYFILE  TXT....|
  006C: 01 59 4F 55 52 46 49 4C 45 44 4F 43 00 0F 00 00   |.YOURFILEDOC....|
 offset: 0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15
Command tail:
  addr  ct tail  -- -- -- -- -- -- -- -- -- -- -- -- --
  0080: 25 20 51 33 3A 4D 59 46 49 4C 45 2E 54 58 54 20   |% Q3:MYFILE.TXT |
  0090: 41 31 35 3A 59 4F 55 52 46 49 4C 45 2E 44 4F 43   |A15:YOURFILE.DOC|
  00A0: 20 2F 41 42 43 44 00 19 EB 0E 09 C3 05 00 4E 6F   | /ABCD........No|
C0:ASM>>
 Display - 4/4 

   The line below the  file control  blocks  display gives the relative offset
for each byte within the block.
:3 
 XTAIL Notes 

   a. Vs 1.1 updates (1/12/91, Gene Pizzetta):
      - Changed hard-coded video attributes to use VLIB routines.  
      - Converted to Zilog mnemonics.  
      - Added type-3 header and type-4 assembly.  Created documentation file.
