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                               BPRINTER.COM                                   

             Size (recs) CRC   Version    Author/Latest Issue      Disk
BPRINT.COM      k (  )         4.0        Joe Wright 5/89          Z3COM 
BPRINTER.REL    k (  )         4.0        Joe Wright 5/89          Z3COM

  1- Syntax  2- System Requirements  3- How BPRINTer Works  4- Notes          


   BPRINTer (Background Printer) is a New Z-System IOP which allows printing a
particular  file  as a 'background' task while running an application  program
in  the 'foreground'.   Any ASCII or print-formatted file may be sent  to  the
LIST  device.   Printing takes place without interference with any  subsequent
program.
:1
 Syntax 

   BPRINTer consists of two files, BPRINT.COM control and loader  program  and
BPRINTER.REL,  the  IOP.  If BPRINT is invoked for  anything  except  specific
Help  (BPRINT //), it checks to see if BPRINTER is  already loaded as  an  IOP
and,  if  not, closes the current IOP,  loads BPRINTER.REL  and  executes  the
command.  There are four commands associated with BPRINTer:

                         BPRINT ON [DIR:][FILE.TYP]

Start  background printing.  The default Printer file is PRINTER.FIL  in  the 
current  directory.   BPRINT ON may select another directory  and/or  another 
file  to be sent to the printer.  The file is sent verbatim.  While  BPRINTER 
is  printing,  any  application output to the LIST device  is  lost.   Typing 
Cntrl-P will suspend BPRINTer and allow normal LIST output to the printer.  A 
subsequent Cntrl-P will cause BPRINTer to resume printing.

                                 BPRINT OFF

Stop printing and close the Print file.  A subsequent BPRINT ON will  re-open 
the print file and start again from the top.


                                  BPRINT D

Set the default Printer file to PRINTER.FIL in the current directory.


                                  BPRINT F

Report the filespec, DIR:FILE.TYP, for the currently defined Print file.
:2
 System Requirements 

   BPRINTer requires a Z80 based Z-System (ZRDOS or ZSDOS) with  at least 1.5k
IOP  space  declared.   The code section of  BPRINTER requires  seven  of  the
twelve  records of the standard IOP.   The remaining five records are used  as
the  Printer  buffer.   In fact, the printer buffer is  dynamically  sized  by
BPRINTER  and  if  you declare an IOP larger than  1.5k,  the  printer  buffer
becomes that much larger,  and therefore requires fewer disk accesses to  read
in a particular file.
:3
 How BPRINTer Works 

   BPRINTer  is  a  New  Z-System  IOP  (Input/Output  Processor).   It  traps
virtually all calls to BIOS and BDOS.   When  first  turned ON,  it  opens the
selected Print file,  checks  LISTST and if the printer is ready,  reads char-
acters from the selected file and  sends  them to  the  printer  until  LISTST
shows the printer to be busy (printing).  

   While the printer is busy, these calls are passed to the BIOS.   When  the
printer  is  once again free, characters are sent to it until  it  goes  busy
again.  Most printers have at least a 'line' buffer and will accept up to 132
characters  at  a time or until a CR, LF or FF character  which  are  usually
'print' commands to the printer which cause it to go 'busy' again.

   Assuming a parallel printer interface,  most BIOS's can ship characters to
the printer's buffer at  5,000 characters per second or faster.   This  means
that  a 100-character line of  print  (between CR's) is  sent  to the printer
within 200 milliseconds, so fast that the WordStar user perceives no delay at
all between his/her keystrokes.
:4
 BPRINTER Notes 

   a. BPRINTer is available for $40.00 from
   
                          Alpha Systems Corporation
                            711 Chatsworth Place
                         San Jose, California 95128
                               (408)-297-5594
