history of the 4-level stack

[Thomas Klemm]

(09-07-2014 10:19 AM)axd1967 Wrote:  Why did trig operations impact T in the 35? Why not 'log', for example?

In short: the pseudo-multiplication used to calculate tangens involves 2 coordinates to keep track of. Thus the list of pseudo-quotients is saved to the stack (c -> stack) and later recalled again (stack -> a):

Code:

tan18:    shift right b[wp]
    shift right b[wp]
tan19:    c - 1 -> c[s]
    if no carry go to tan18
    a + c -> c[wp]
    a - b -> a[wp]
    b exchange c[wp]
tan13:    b -> c[w]
    a - 1 -> a[s]
    if no carry go to tan19
    a exchange c[wp]
    stack -> a
    if b[s] = 0
         then go to tan15
    shift left a[w]
tan14:    a exchange c[wp]
    c -> stack
    shift right b[wp]
    c - 1 -> c[s]
    b exchange c[s]

In case of logarithms it's just one constant that has to be multiplied by the pseudo-quotient and added to a total.

I recommend to have a look at:
HP35 trigonometric algorithm
HP 35 Logarithm Algorithm

Quote:Note that the stack is used (at 01374) destroying thus its top.

Cheers
Thomas