B.4.87. `FISUB': Floating-Point/Integer Subtraction
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FISUB mem16 ; DE /4 [8086,FPU]
FISUB mem32 ; DA /4 [8086,FPU]
FISUBR mem16 ; DE /5 [8086,FPU]
FISUBR mem32 ; DA /5 [8086,FPU]
`FISUB' subtracts the 16-bit or 32-bit integer stored in the given
memory location from `ST0', and stores the result in `ST0'. `FISUBR'
does the subtraction the other way round, i.e. it subtracts `ST0' from
the given integer, but still stores the result in `ST0'.