Assembly Language Help (alang.hlp) (Table of Contents; Topic list)
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FSUB Instruction
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  Title:    Subtract
 
  Syntax:   FSUB [dest,src]
            FSUBP dest,ST
            FSUB src
            FISUB src
 
  See also: FSUBR, FADD
 
  Description:
 
     Subtracts the source from the destination and returns the
     difference in the destination. If two register operands are
     specified, one must be ST. If a memory operand is specified, the
     result replaces the value in ST. Memory operands can be 32- or
     64-bit real numbers or 16- or 32-bit integers.
 
     If no operand is specified, ST is subtracted from ST(1) and the
     stack is popped; the difference is returned in ST. For FSUBP, the
     source must be ST; the difference (destination minus source) is
     returned in the destination register and ST is popped.
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