Z       D       P

                              (c) 1980,1986 Robert D. Nashner
                                            (213) 395-5311
                                            (818) 902-5059

                               AN INTRODUCTION  

              ZDP  (Z80  Debugging Package) was originally  written  in 
      1980  for a Micropolis based (MDOS) operating system which,  like 
      CP/M,   comes  with  8080-based development and  debugging  tools 
      only.  The original version was designed to fit into one 4K  byte 
      EPROM (minus the space for stack and saved registers).  This CP/M 
      version  of  ZDP  has been released as a  public  domain  utility 
      (intended for non commercial use; but allowed to circulate freely 
      amoung home or personal BBS users.)

              The   most   distinguishing  feature  of   ZDP   is   its 
      positionability.   Unlike  DDT or ZSID which always replaces  the 
      CCP,  a  ZDP  copy can be generated to run on any 256  byte  page 
      boundary within the 64K address space;  and it will occupy the 17 
      consecutive  pages  following  that  boundary  page.  A  properly 
      positioned  ZDPxx program can remain intact after a CP/M cold  or 
      warm  start  or after starting another transient  program.   Thus 
      transient command programs containing Restart vectors may trap to 
      ZDP;  also,  CCP  execution may be traced following the transient 
      program's 'JMP 0" step. This type operation is further simplified 
      by  a ZDP command to set any one of the seven Restart vectors  to 
      be used as breakpoint traps.

              Another  interesting and useful feature is the ability to 
      create its own symbol table anywhere in memory which can name any 
      constants  or addresses that show up in disassembly  listings  or 
      traced  instructions.   This  feature makes it easy  to  identify 
      values  in code for which no Assembler-generated symbol table  is 
      available.  

              A  printer device toggle has been added.   During command 
      entry,  typing a CTL-P will toggle the printer or list device  ON 
      or  OFF  (similiar to the operation of CTL-P in the CP/M  command 
      mode).

      Later versions shall include such extensions as:

                  1.  Utilization  of  CP/M's  own  command  processor, 
                      (including all editing control characters).

                  2. The ability to read code or data from CP/M files
                  
      An enhanced release of ZDP may allow data entry in Z80  mneumonic 
      form (including use of defined symbolic values).

              The  current version of the program to create  a  working 
      ZDP program is ZDPGEN12.  Consult the first section of the User's 
      Manual in this library for the operation of ZDPGEN.






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