Commodore PET User Manual page 208

Even if C is a two-digit number. only the rightmost digit is concatenated onto C$.
The tens value has already been assigned to 0 and will be added during the next
loop iteration.
N is set to 2 to include the last carry only if 0=1 and 1=1 (signaling a carry
on the last loop iteration). This is important. because if both conditions are true
the loop will NOT iterate again to add 0 carry into A in line 1040. thereby losing
the last carry value in O. Sy setting
t' J
to 2 on the last loop iteration, both digits of
C are included in C$. and the last carry over is not lost.
1070 IF C)=10 THEN D=1
cI1612\>=10
D~
1080 IF D=1 AND 1=1 THEN N=2
D~ I~ N~
1090 C$=RIGHT$(STR$(C).N)+C$
C$=RIGHT$(1IDill.I,2l+C$
C$=ITm+C$
C$=11j2Ixlxjxlxlxlxlxl
The entire FOR ... NEXT loop routine at lines 1020 through 1100 does the
following:
1. It extracts individual digits from a numeric string and assigns numeric
values to them (statements 1030. 1050).
2. The digits from both strings are added together one digit at a time
(statement 1060), checked for a carry value (statement 1070), and the
carry is added to A in the next column (Iine 1040).
3. The individual sums are then linked and converted back into a numeric
string for printing Oine 1090).
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