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 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	x		56	PI		76	Sqrt
17	d		37	Clear x		57	Pause		77	Sub* or Return*

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