__MAP__   [CODE const_expression]  [CONST const_expression]  [DATA  const_expression]  [STRING  const_expression]

__MAP__ tells the compiler to reserve space, by advancing the 4 pointers.   In all cases it must be a constant expression.  There is no error checking, so the user is responsible for the validity of the values. 

All of these values are byte values. For CODE sets the compiler program counter. CONST sets the pointer for constant strings and CONST arrays, it counts down from the end of Flash memory. Both of these addresses are byte addresses and are absolute.

DATA sets the pointer for INTEGER and SINGLE variables. STRING sets the pointer for arrays of BYTE, INTEGER or FLOAT and counts down from the end of the variable space.   These are byte addresses, but are relative to the space that BASIC allocates for variables.

When used with no parameters, the compiler will report where the various pointers are left following the compile.

This allows you to reserve space for Flash Write , or for implimenting program overlays.


The values for the above map represent are based on the SuperPRO with 8.25 firmware.

The first program writes code to the first Flash sector then calls code in the second Flash sector

share_x = 22
share_y = 33

print "start the program and call overlay"
gosub start1
print "we are back"

print share_x

end ' if you don't have an END here or a loop the program will drop through into unprogrammed memory

__MAP__ CODE &H11000 CONST &H27000


print "in the overlay"


This program when run shows

start the program and call overlay
in the overlay
we are back

Now overlay the second Flash sector with this program

DIM share_x          ' to access global variables in the original program, they must be declared in the same order
DIM share_y

     ' if you declare anything that would produce code before the __MAP__ you will overlay the 1st sector -- which you don't want to do

__MAP__ CODE &H11000 CONST &H27000



share_x = share_y


Now when run it shows, and it shows the access to share_x was changed

start the program and call overlay
we are back
Differences from other BASICs

See also