HP-80 Nonpareil Emulator: fixed a bug in the calendar functions

[Thomas Klemm]

Inspired by a recent thread I started using the HP-80 emulator but had troubles with the calendar functions. Whatever I entered the result was always a blinking 9.999999999 99.

So I started to debug the DATE function and noticed a fishy line 6201 in the following block of code:

Code:

1708   L06175:  .1....11..                          4 -> p
1709   L06176:  1...11..1.                          b exchange c[wp]
1710   L06177:  1..1..111.                      dd2:    shift right c[w]
1711   L06200:  .....111..                          p - 1 -> p
1712   L06201:  111.1.11..                          if p # 14
1713   L06202:  .111111111  -> L063177                   then go to dd2
1714   L06203:  .11.1.1.1.                          if c[x] = 0

The loop was executed once too often and thus the month (here 6) was shifted over the right end of register c and thus got lost:

Code:

1712   L06201:  111.1.11..                              if p # 14            
pc=06202  p=15  stat: 0 2 3 7 9                                              
a: 00000030680000                                                            
b: 00000000023099                                                            
c: 00000000030006                                                            
m: 07000000000000                                                            
1713   L06202:  .111111111  -> L063177                       then go to dd2  
pc=06177  p=15  stat: 0 2 3 7 9                                              
a: 00000030680000                                                            
b: 00000000023099                                                            
c: 00000000030006                                                            
m: 07000000000000                                                            
1710   L06177:  1..1..111.                      dd2:    shift right c[w]     
pc=06200  p=15  stat: 0 2 3 7 9                                              
a: 00000030680000                                                            
b: 00000000023099                                                            
c: 00000000003000                                                            
m: 07000000000000                                                            
1711   L06200:  .....111..                              p - 1 -> p           
pc=06201  p=14  stat: 0 2 3 7 9                                              
a: 00000030680000                                                            
b: 00000000023099                                                            
c: 00000000003000                                                            
m: 07000000000000                                                            
1712   L06201:  111.1.11..                              if p # 14            
pc=06202  p=14  stat: 0 2 3 7 9                                              
a: 00000030680000                                                            
b: 00000000023099                                                            
c: 00000000003000                                                            
m: 07000000000000                                                            
1713   L06202:  .111111111  -> L063177                       then go to dd2  
pc=06203  p=14  stat: 0 2 3 7 9                                              
a: 00000030680000                                                            
b: 00000000023099                                                            
c: 00000000003000                                                            
m: 07000000000000                                                            
1714   L06203:  .11.1.1.1.                              if c[x] = 0          
pc=06204  p=14  stat: 0 2 3 7 9                                              
a: 00000030680000                                                            
b: 00000000023099                                                            
c: 00000000003000                                                            
m: 07000000000000

To be sure I had a look at the original US-patent 3863060 and noticed a special case at exactly that line:

The leading L is missing in line number 6201. And while the texts agree (if p # 14 | IF P # 14) the bit pattern don't: 111.1.11.. | 11111.11... And of course [if p # 15] makes more sense.

Thus I patched these two files in my installation:
/usr/local/lib/nonpareil diff 80.lst.orig 80.lst

Code:

2074c2074
< 1712   L06201:  111.1.11..                            if p # 14
---
> 1712   L06201:  11111.11..                            if p # 15

/usr/local/lib/nonpareil diff 80.obj.orig 80.obj

Code:

1666c1666
< 3201:1654
---
> 3201:1754

And, lo and behold, the bug in the calendar functions was fixed.

Cheers
Thomas