Commodore PET User Manual page 206

The VAL function converts each extracted string literai into a numeric
value:
When 1
=
16,
B=VAL(MID$(B$,16,1))
B=VAL($1~171914131517121)
B=m
When 1
=
15,
B=VAL(MID$(B$,15,l)) .
After each digit of the numeric string is converted into a numeric constant.
the necessary calculations to add them together are performed before the loop
reiterates, The calculations to arrive at C$ are done in lines 1060 to 1090,
10013 N=l
1010 D=0
10213 FOR I=LEN(A$) TO 1 STEP -1
1
(14(1
A=A+Il : II=0
11350 B=VALCMID$CB$.I.l»
106(1 C=A+B
10713 IF C>=l13 THEN D=l
10813 IF D=l AND 1=1 THEN N=2
10913 C$=RIGHT$CSTR$(C).N)+C$
111313 NEXT 1
Initialize string pointer N.
Initialize carry value.
Initialize decrement counter 1.
Extract digits separately. Convert
to non-string nu meric.
Add tens value from carry (0) to A.
Extract digits separately. Convert
to non-string numeric.
Add extracted digits of A$ and B$.
Carry tens value into D if C>=10.
Link sums into string answer.
Variable D is initialized to zero at line 1010 and used as a carry value in lines
1040, 1070. and 10S0. During addition, if the value of C is greater than or equal to
ten, a tens value is carried over to the next left position. The tens value éarried
over is stored in D:
2 3 +1 4 +1 5 +'6
'1
7 +1 8 901 2
+
5 7 9 43572
23 5 1 4 7 32584
193