The HP67 calculator has three angle modes: DEG, RAD and GRD.
DEG is degrees. There are 360 degrees in a circle.
RAD is radians. There are 2*PI radians (about 6.28) in a circle.
GRD is gradians. I’d never heard of these before I got my original HP67 but apparently these are used in some fields and there are 400 gradians in a circle.
You select the angle mode by pressing [h] then [ENTER], [CHS] or [EEX]. The key codes you’ll see in W/PRGM are “35 41”, “35 42” or “35 43”.
The angle mode is one of the pieces of status information written to each side of a magnetic card, whether you write program information or data.
h DEG 45 f SIN = 0.71, STO 0, g SIN-1 = 45.00
RCL 0 h RAD g SIN-1 = 0.79 (=PI/4)
RCL 0 h GRD g SIN-1 = 50.00
Internals
When you select an angle mode the calculator remembers your choice by setting a combination of bits in its internal S register. You can see this by choosing different angle modes in the HP67u and looking at the S register via menu / Advanced.
The combinations are:
DEG S0=0 & S14=0
RAD S0=1 & S14=0
GRD S0=0 & S14=1
Microcode
[h] [DEG] 00214 display off 00215 b exchange c[w] 00216 CRC 400 00217 keys to a ... 00252 delayed rom 01 00253 a -> rom address 00522 ... 07205 0 -> s 0 07206 0 -> s 14 07207 if n/c go to 07313 07313 delayed rom 00 07314 if n/c go to 0074 00074 ... 00161 hi im woodstock 00162 display off 00163 display toggle 00164 ... (00167 - 00213; wait loop) [h] [RAD] 00214 display off 00215 b exchange c[w] 00216 CRC 400 00217 keys to a ... 00252 delayed rom 01 00253 a -> rom address 00521 ... 07203 1 -> s 0 07204 if n/c go to 07206 07206 0 -> s 14 07207 if n/c go to 07313 07313 ... [h] [GRD] 00214 display off 00215 b exchange c[w] 00216 CRC 400 00217 keys to a ... 00252 delayed rom 01 00253 a -> rom address 00520 ... 07210 0 -> s 0 07211 1 -> s 14 07212 if n/c go to 07313 07313 ...
