The HP67 stores PI/4 in ROM subroutine 05043 with 13 digit precision. It multiplies that by 4 (“c + c -> c[w]” twice) to get 3.1415926535900 and then rounds that to 3.141592654.
It works like this:
HP67 Logging started. (00167 - 00213 wait loop) [h] ... (00167 - 00213 wait loop) [PI] 00214 display off 00215 b exchange c[w] 00216 CRC 400 00217 keys to a ... 00252 delayed rom 01 00253 a -> rom address 00537 if n/c go to 0427 00427 ... 00435 if n/c go to 0542 00542 ... 00544 if n/c go to 0436 00436 ... 00442 jsb 01205 ; clear s 4,6-8,10,13 00443 ... 00446 if n/c go to 06021 06021 ... 06027 a -> rom address 06004 if n/c go to 06046 06046 ... 06051 a -> rom address 07110 if n/c go to 07172 07172 ... 07173 delayed rom 012 07174 jsb 05043 .05043 p <- 12 .05044 0 -> c[w] .05045 load constant 7 .05046 load constant 8 .05047 load constant 5 .05050 load constant 3 .05051 load constant 9 .05052 load constant 8 .05053 load constant 1 .05054 load constant 6 .05055 load constant 3 .05056 load constant 3 .05057 load constant 9 .05060 load constant 7 .05061 load constant 5 ; C=07853981633975 .05062 p <- 12 .05063 return 07175 c + c -> c[w] ; C=15707963267950 07176 c + c -> c[w] ; C=31415926535900 07177 shift right c[w] ; C=03141592653590 07200 c + 1 -> c[m] ; C=03141592654590 07201 0 -> c[x] ; C=03141592654000 07202 if n/c go to 07372 07372 delayed rom 00 07373 if n/c go to 0103 00103 ... 00110 then go to 0114 00114 ... 00115 if n/c go to 0124 00124 ... 00156 jsb 02007 ; A=03140000000000 00157 delayed rom 02 00160 jsb 01162 ; A=3014fffffff100 B=03000000000022 00161 hi im woodstock 00162 display off 00163 display toggle ; "3.14" 00164 0 -> s 15 00165 if 1 = s 15 00166 then go to 0164 (00167 - 00213 wait loop)
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