The address of this routine is found in the table of addresses. It is called via the calculator literal +3B by the routine at S_LETTER.
This subroutine is only called from 2757 and is used to perform a single arithmetic operation. The offset that specifies which operation is to be performed is supplied to the calculator in the B register and subsequently transferred to the system variable BREG.
The effect of calling this subroutine is essentially to make a jump to the appropriate subroutine for the single operation.
|Discard the RE_ENTRY address.
|Transfer the offset from BREG to A.
|Enter the alternate register set.
|Jump back to find the required address; stack the RE_ENTRY address and jump to the subroutine for the operation.