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 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 xy 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*