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 row and column on the keyboard. For example, the Enter key on the HP-65 would be code 41. All codes that don't start with 0 obey this rule. On the HP-97, keys on the right keypad were given codes beginning with -.
• A number. All codes starting with 0 represent the corresponding number. For example 04 means the 4 key.

The HP-55 had an exception to the above rules. GTO was displayed as a dash (-) thus GTO 25 would display at -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 up 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 drop 45 Print/Space 65 Ln x 06 6 26 Enter Exp 46 End 66 To Rect 07 7 27 Enter (up) 47 Continue 67 Hyper or x <-()* 10 8 30 x<>y 50 If x = y 70 Sin x 11 9 31 Roll dn 51 71 Tan x 12 e 32 Chg Sign 52 If xy 73 Cos x 14 b 34 - 54 Set Flag 74 ex 15 f 35 ÷ 55 |y| 75 Log x 16 c 36 x 56 PI 76 Sqrt 17 d 37 Clear x 57 Pause 77 Sub* or Return*