M_apm_scale
extern void M_apm_scale(M_APM, int);
M_apm_scale(M_work1, 2); /* shift 2 digits == 1 byte for efficiency */
M_apm_scale(M_work2, 2);
M_apm_scale(M_work1, 2);
M_apm_scale(M_work2, (aexp + 2 - bexp));
M_apm_scale(M_work2, 2);
M_apm_scale(M_work1, (bexp + 2 - aexp));
M_apm_scale(M_work2, (aexp - bexp));
M_apm_scale(M_work1, (bexp - aexp));