!TITLE Using Prolog - Overview
!KEY
The  Emas  Prolog system offers the user an interactive programming environment
with tools for incrementally building programs, debugging programs by following
their executions, and modifying parts of programs without having to start again
from scratch.

The text of a Prolog program is normally created in  a  number  of  EMAS  files
using  one  of  the  standard text editors.  The Prolog interpreter can then be
instructed  to  read-in  programs  from  these  EMAS  files;  this  is   called
"consulting"  the  file.    The  text editor can be called directly from within
Prolog, and it can be arranged for the file to  be  consulted  or  re-consulted
when  you  leave  the  editor  and  return to Prolog.  Re-consulting means that
definitions  for  procedures  in  the file will replace any old definitions for
these procedures.  Using the editor in this way makes it easy to  incrementally
develop, debug and then correct Prolog programs without ever leaving the Prolog
system.    It  is  recommended that you make use of a number of different files
when writing programs.  Since you will be editing and  consulting/re-consulting
individual  files  it  is  useful  to  use  files  to  group  together  related
procedures; keeping collections of  procedures  that  do  different  things  in
different files.  Thus a Prolog program will consist of a number of files, each
file containing a number of related procedures.
When your programs start to grow to a fair size, it is also a good idea to have
one  file  which  just  contains commands to the interpreter to consult all the
other files which form your program.  You will then be  able  to  consult  your
entire  program by just consulting this single file.  More about how to do this
later, though.

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