GWBASIC User's Manual

GW-BASIC User's Guide
MOV CL, [BX] ; Gets length of B$ in CL.
MOV DX, 1[BX] ; Gets address of B$ text in DX.
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MOV SI, 10[BP] ; Gets address of A in SI.
MOV DI, 6[BP] ; Gets pointer to C in DI.
MOVSW ; Stores variable A in C.
RET 6 ; Restores stack and returns.
MOVSW copies only two bytes. This is sufficient if variables A and C are integer. Four bytes must
be copied if they are single precision; eight bytes, if they are double precision.
Example 3:
100 DEF SEG=&H2000
110 ACC=&H7FA
120 CALL ACC(A, B$, C)
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Line 100 sets the segment to hex 2000. The value of variable ACC is added into the address as
the low word after the DEF SEG value is shifted four bits to the left (this is a function of the
microprocessor, not of GW-BASIC). Here, ACC is set to &H7FA, so that the call to ACC
executes the subroutine at the location hex 2000:7FA (absolute address hex 207FA).
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