Multiply Function [x]

[Gamo]

I'm wondering what algorithm is use in calculator for the multiply function.

So I came up with the basic whole number multiplication by using the
adding up method.

7 x 4 = (7 + 7 + 7 + 7) = 28

Then I came up with this program to do the multiply function.
This program will multiply two whole numbers and do multiply with the first whole number with decimal like (21.75 x 5)

This program will not give correct result when multiply both decimal numbers like (10.2 x 11.2)

Example: 6903 x 103

6903 [ENTER] 103 [R/S] ---> 711009

Step can be reverse: 103 [ENTER] 6903 [R/S] ---> 711009

Program: Multiply Function using HP-12C

Code:


01 STO 0
02 X<>Y
03 STO 1
04 RCL 0
05 INTG
06 X=0 ?
07 GTO 17
08 RCL 2
09 RCL 1
10   +
11 STO 2
12 RCL 0
13   1
14   -
15 STO 0
16 GTO 05
17 RCL 2
18   0
19 STO 2
20 X<>Y

Is there any other more efficient way to do this better and faster?
Anyone get a better solution so that this can do multiplication with both decimal numbers like (123.45 x 12.34)

Thank You

Gamo