The Museum of HP Calculators


Key Codes

Because the older calculators could only display numbers, each key was assigned a code so that the programs could be read. The code was simple - each number represented either:

The HP-55 had an exception to the above rules. GTO was displayed as a minus (−) thus GTO 25 would display as −25.

The HP-9100A & B don't use this convention. They list their keycodes on the pull-out reference card in their bases. If your card is missing, the keys are: (* marks codes/keys found only on the HP 9100B. Each of these codes can represent two functions which is determined by context. i.e. a 77 after a GO TO is a Sub not a Return.)

Code Key     Code Key     Code Key     Code Key
00 0 20 Clear 40 y→() 60 Acc+
01 1 21 . 41 Stop 61 Rcl
02 2 22 Roll ↑ 42 Fmt 62 To Polar
03 3 23 x→() 43 If Flag 63 Acc-
04 4 24 y⇄() 44 Go To () () 64 Int x
05 5 25 45 Print/Space 65 Ln x
06 6 26 Enter Exp 46 End 66 To Rect
07 7 27 47 Continue 67 Hyper or
x ←()*
10 8 30 x⇄y 50 If x = y 70 Sin x
11 9 31 Roll ↓ 51 71 Tan x
12 e 32 Chg Sign 52 If x<y 72 Arc
13 a 33 + 53 If x>y 73 Cos x
14 b 34 54 Set Flag 74 ex
15 f 35 ÷ 55 |y| 75 Log x
16 c 36 × 56 π 76 √x
17 d 37 Clear x 57 Pause 77 Sub* or
Return*

Go back to the software library
Go back to the main exhibit hall