gtoal.com/imp77/reference-manual/The_IMP80_Language_Manual.html

        %long %real %function FRAC PT(%long %real L)

           The fractional part of the parameter L is returned as the
           result.  Note that the fractional part is always treated as
           being greater than or equal to zero; e.g. FRAC PT(-4.6) is
           0.4.

        %long %real %function MOD(%long %real I)

           This function returns the modulus (absolute value) of the
           parameter.

           {IMP77: the modulus of an real expression can also be
                   obtained by enclosing the expression between vertical bars;
                   e.g. |X-Y|.}
                                 

gtoal.com/imp77/reference-manual/Vax-Imp77-library.txt

gtoal.com/imp77/reference-manual/THE IMP LIBRARY MANUAL ON THE DECsystem-10-20.txt

                              FRAC PT

  DEFINITION:  This longreal function gives the value of the
               fractional part of the given longreal expression.

  SPEC:   Not required

  USE:    r=FRAC PT(x)

          x is a longreal expression for which the
          fractional part is to be returned

        The fractional part of 'x' is returned as a long real
        via %RESULT.

        e.g.  the FRAC PT(3.14159)  is 0.14159

  ASSOCIATED PROCEDURES:  INT, INT PT, FLOAT

  ERROR CONDITIONS:  None


gtoal.com/imp77/reference-manual/EMAS-2900-Imp-Library.txt

  FRACPT

  DEFINITION: This longreal function gives the value of the fractional part of the
              longreal quantity specified on entry.

  SPEC:  Not required

  CALL:  FRAC PT(X)
       X      is a longreal expression of which the fractional part is to be
              returned.
              The fractional part of x is returned as a long real.  If mod(x) exceeds 2-1,
              the value returned is always zero.  The fractional part is always
              calculated as
                               x - (largest integer less than or equal to x);
              e.g.  FRACPT(4.6)=0.6
                    FRACPT(-4.6)=0.4

  ERROR CONDITIONS: None.