The  arrival of dBASE 2.4 was a welcome event 
at  our  office.  We run a  variety  of  different 
databases  and  2.4 enabled  us  to  significantly 
improve our programs.

     In one area,  however, 2.4 produced some real 
problems. We use a number of dual data bases where 
we transition between them in various parts of the 
program.  Under  2.3 we would run into a `TOO MANY 
FILES`  error  every  so  often  and  awaited  2.4 
eagerly to solve that problem.  As it turned  out, 
2.4  is  more  insistent upon  a  proper  `RETURN` 
statement  than  2.3  and it forced  us  to  think 
through the problem.

     We  did not necessarily want to return to the 
module that called the module we were running,  so 
we  created an `invisible box.` This box  contains 
the `forever loop` for the program and is used for 
all transfers between the data bases.

     With the box we can go from any point in  the 
program  modules  for a data base to any point  in 
the  program modules of any other  data  base.  As 
long  as  we have no more than two data  bases  on 
line  at a time,  we can use the box to transition 
between any number of data bases.  Before we enter 
the box in a transition between data bases we also 
save  the common variable.  When we enter the  new 
data  base  from  the box we do a `FIND`  for  the 
common variable to bring up the proper record.

     There is,  of course,  a time penalty,  but a 
rather  minor one in terms of what the box does.   


* dBOX.BOX by Steve Leon (201) 886-1658
* dBOX is a program to switch between data bases 
* designed for dBASE 2.4 
 
* prior to entry the initilization program has
* poked the drive number into memory via the
* command `POKE 063,(64+@(dr,`AB`))`

* set up forever loop for program
STORE t TO keepitup
DO WHILE keepitup

* set up alternateive routes
* the initialization program stores 0 to box
* moveit is used in this data base to find the 
* proper file in the other data base via a
* `SAVE`, `RESTORE` and `FIND`
* first is used to bring on a fixed screen 
* matrix for the module

DO CASE 

CASE box = 0   
        STORE f TO moveit
        STORE t TO first
	STORE chr(peek (063)) TO dr
	USE &dr.:cpb INDEX &dr.:file
        DO main.cpb

CASE box = 1
	RELEASE ALL
        STORE t TO keepitup
	STORE chr(peek (063)) TO dr
	USE &dr.:cpb INDEX &dr.:file
        STORE t TO moveit
        STORE t TO first
	DO main.cpb

CASE box = 2  
	RELEASE ALL
        STORE t TO keepitup
	STORE chr(peek (063)) TO dr
	USE &dr.:cpb1 INDEX &dr.:file1
        STORE t TO moveit
        STORE t TO first
	DO main.ind

CASE box = 3
 	RELEASE ALL
        STORE t TO keepitup
	STORE chr(peek (063)) TO dr
	USE &dr.:cpb INDEX &dr.:file 
        STORE t TO moveit
        STORE t TO first
	DO search.cpb
CASE box = 4
	RELEASE ALL
        STORE t TO keepitup
	STORE chr(peek (063)) TO dr
	USE &dr.:cpb1 INDEX &dr.:file1
        STORE t TO moveit
        STORE t TO first 
	DO search.ind

CASE box = 5
        STORE f TO moveit
        STORE t TO keepitup
        DO search.cpb

CASE box = 6
        STORE f TO moveit
        STORE t TO keepitup
        DO search.ind

CASE box = 7
        STORE f TO keepitup

ENDCASE
ENDDO
* when we quit eliminate sign-off message
ERASE
SET CONSOLE OFF
QUIT

     The  transition from the various  modules  to 
the BOX is:

To quit:
     CASE command = `Q`
     * prevent sign-off message
     STORE t TO keepitup
     STORE 7 TO box
     RETURN

To transition to other data base:
     CASE command = `I`
     STORE !(fl:no) TO linker
     SAVE to move
     STORE 2 TO box 
     RETURN

     There  are other transitions in the  program, 
but  the above should be sufficient to enable  you 
to  write  your own `box.` If you come up  with  a 
better  way,  or  have  some  thoughts,  we  would 
appreciate them.