59h MT$FNGT floating point negation
Input X register - address of the floating-point register to be negated.
Output - none -
Description

Toggles the sign of the register pointed to by X.

Note that as this routine operates on a register, it assumes a mantissa length of 7 bytes. To negate a normal BCD number, X should point to the byte below the first byte of the number in memory.

Registers B and X are preserved.

See also: technical manual > utility system services > floating point numbers

Example To change the sign of the accumulator, execute the following code:
        LDX     #MTT_AMAN
        OS      MT$FNGT
and to negate the constant 202.88:
    FP_CONST:
        DB      0,0,0,80h,28h,20h       ;mantissa
        DB      2                       ;exponent
        DB      0                       ;sign

        LDX     #FP_CONST-1
        OS      MT$FNGT
Errors - none -