A. The first considerable roundoff analyser software, which can provide global error bounds for a given numerical algorithm, was designed by Webb Miller and David Spooner in the second half of the 70s. Despite its abilities, the recently software is not widely used, and since its publication it has not been upgraded. The software was written in Fortran IV for the IBM 360/370 series. Without any modifications, it is not usable in a PC environment with the most widely used compilers based on the Fortran 77 standard (GNU compiler, Watcom, etc.), because there are several non-standard solutions in the source. In addition, the user is bound by extraordinary strict limitations of the size of the algorithm to analyse. We have upgraded the package in order to make it suit the Fortran 77 standard, and to expand the size limits. With the upgraded version we have analysed two variants of the ABS method: the implicit LU and Huang methods.