	Keyboard Scan Codes

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PC Keyboard Scan Codes

News: Keyboard Emulator now on-line

You can now determine specific Keyboard Scancodes and sequences without the need to look them up individually in a table and assemble them by hand. Just click on the keys and cut and paste the results. The Keyboard Emulator is here

Note dated January 2003

The XT scancodes and the 84 key keyboard mentioned in the following text refer to obsolete equipment. There may be some special purpose equipment still using XT codes? Some Electronic PC board level products were known to use XT codes maybe some still do?
It’s easy to get confused over scancodes because the AT scancodes used at the hardware level are converted by the PC Bios into XT codes. If you are an engineer looking at the keyboard bus lines with a ’scope or 'Reverse Mule' analysis unit you will likely see AT style scancodes. But if you are a programmer you will probably be dealing with XT codes. This is to maintain backward compatibility with the earliest PCs of the mid 1980s. If anyone knows of any equipment still using XT codes at the hardware level please let me know.
Since this page was first written six new keys have been added to the original keyboards. The scancodes for these keys can be found at the foot of this page. The Mule can emulate ALL the new keys.

All the scancodes published here have been verified with The Shadow Mule and are known to be accurate. Data published elsewhere is often seen to contain errors. Please do not copy this data into another medium or web site. It is maintained up to date here and we strictly enforce our copyrights. We are happy for any site to link here.

Overview

The PC keyboard interface is designed so the system software has maximum flexibility in defining certain keyboard operations. This is accomplished by having the keyboard return scancodes rather than ASCII codes. Each key generates a 'make' scancode when pressed and a 'break' scancode when released. The computer system interprets the scancodes to determine what operation it is to perform. For historical compatibility reasons computers can employ different sets of scancodes for different purposes. Earlier PC computers tend to use the XT scancode set. Current PC computers tend to use the AT scancode set. The MF1, MF2 and MF3 sets are alternatives, similar in many respects to the XT and AT sets. The table below shows the scancodes generated when a key is pressed- the 'make' code. The 'break' code may be derived from the 'make' code as described later. Notice that scancodes may consist of a single or several bytes.

Many keyboard scancode tables published are not completely accurate. Confusion arises between scancodes issued by the keyboard hardware and the scancodes appearing in the keyboard buffer. The scancodes presented here are those actually sent by the keyboard hardware. The computer BIOS may translate the code for compatibility reasons. For example, the XT scancode set was first used in the original IBM PC computer. Other IBM computers and terminals used a different scancode set. Apparently IBM tried to bring the PC into line with its other products when the IBM PC/AT was launched. The keyboard for that machine used a scancode set virtually identical to other IBM machines. However to maintain compatibility with earlier PC software the BIOS for the AT machines converted the AT scancodes into the earlier XT scancodes. At the current time (June 1995) this system of code conversion in the BIOS persists. The code you read from the keyboard buffer is not necessarily the same code transmitted from the keyboard.

How to Calculate the Scancode

Use the keyboard sketches to determine the 'Key Number'. Note that the 102 key keyboard shown is the keyboard used in the UK. In the USA and some other countries a 101 key keyboard is used- there are minor scancode differences- read the table notes.
Lookup the 'Key number' in the table and read of the 'Make'scancode. Note that the scancode differs depending on the scancode set currently in use. Note also that some scancodes consist of more than 1 byte.
Calculate the 'break' scancode as detailed below

'Break' scancodes for PC/XT computers

The 'break' code for XT style computers is the 'Make' code OR’d with the hexadecimal value 80. (If you are unfamiliar with hexadecimal numbers then simply change the first character of the scancode thus: Change 0 to 8, 1 to 9, 2 to A, 3 to B, 4 to C, 5 to D, 6 to E, 7 to F)

For example the scancodes generated by pressing and releasing the Escape key (Key Number 110) are 01 81

'Break' scancodes for PC/AT computers

Most PC’s made since about 1989 use keyboards that generate AT scancodes (Though the codes may be converted to XT scancodes in the BIOS). The 'break' code for AT class scancodes is simply the 'make' code preceded by hex F0. For example the scancodes generated when the Escape key is pressed and released are 76 F0 76.

Special scancodes of potential interest to Altek Mule™ users

If the keyboard’s buffer overflows it sends a special scancode to the computer. This generally causes the computer to sound a warning beep. Altek Mule(tm) users may issue this code if they want to sound the beep to draw the operators attention. For computers using AT scancodes the code is 00. (For obsolete PCs using XT scancodes the code was hex FF)

PC Keyboard, 102 key

PC Keyboard, 84 key

Scancode Table

Table Notes

The Scancode values in this table are hexadecimal
Some key numbers are unallocated or reserved
The XT codes are obsolete. However because the computer BIOS translates the AT codes to XT codes internally these are often the codes seen and used by software engineers.
The MF codes are rarely used by PCs but some keyboards are capable of issuing them for use by other equipment like terminals.
* Only keyboards with 101 keys- USA keyboard (and others)
** Only keyboards with 102 keys- UK keyboard (and others)

Key Num	XT	AT	MF1	MF2	MF3

1	29	0E	29	0E	0E
2	02	16	02	16	16
3	03	1E	03	1E	1E
4	04	26	04	26	26
5	05	25	05	25	25
6	06	2E	06	2E	2E
7	07	36	07	36	36
8	08	3D	08	3D	3D
9	09	3E	09	3E	3E
10	0A	46	0A	46	46
11	0B	45	0B	45	45
12	0C	4E	0C	4E	4E
13	0D	55	0D	55	55
15	0E	66	0E	66	66
16	0F	0D	0F	0D	0D
17	10	15	10	15	15
18	11	1D	11	1D	1D
19	12	24	12	24	24
20	13	2D	13	2D	2D
21	14	2C	14	2C	2C
22	15	35	15	35	35
23	16	3C	16	3C	3C
24	17	43	17	43	43
25	18	44	18	44	44
26	19	4D	19	4D	4D
27	1A	54	1A	54	54
28	1B	5B	1B	5B	5B
* 29	2B	5D	2B	5D	5C
30	3A	58	3A	58	14
31	1E	1C	1E	1C	1C
32	1F	1B	1F	1B	1B
33	20	23	20	23	23
34	21	2B	21	2B	2B
35	22	34	22	34	34
36	23	33	23	33	33
37	24	3B	24	3B	3B
38	25	42	25	42	42
39	26	4B	26	4B	4B
40	27	4C	27	4C	4C
41	28	52	28	52	52
** 42	2B	5D	2B	5D	53
43	1C	5A	1C	5A	5A
44	2A	12	2A	12	12
** 45	56	61	56	61	13
46	2C	1A	2C	1A	1A
47	2D	22	2D	22	22
48	2E	21	2E	21	21
49	2F	2A	2F	2A	2A
50	30	32	30	32	32
51	31	31	31	31	31
52	32	3A	32	3A	3A
53	33	41	33	41	41
54	34	49	34	49	49
55	35	4A	35	4A	4A
57	36	59	36	59	59
58	1D	14	1D	14	11
60	38	11	38	11	19
61	39	29	39	29	29
62	E038	E011	E038	E011	39
64	E01D	E014	E01D	E014	58
75	E052	E070	E052	E070	67
76	E053	E071	E053	E071	64
79	E04B	E06B	E04B	E06B	61
80	E047	E06C	E047	E06C	6E
81	E04F	E069	E04F	E069	65
83	E048	E075	E048	E075	63
84	E050	E072	E050	E072	60
85	E049	E07D	E049	E07D	6F
86	E051	E07A	E051	E07A	6D
89	E04D	E074	E04D	E074	6A
90	45	77	45	77	76
91	47	6C	47	6C	6C
92	4B	6B	4B	6B	6B
93	4F	69	4F	69	69
95	E035	E04A	E035	E04A	77
96	48	75	48	75	75
97	4C	73	4C	73	73
98	50	72	50	72	72
99	52	70	52	70	70
100	37	7C	37	7C	7E
101	49	7D	49	7D	7D
102	4D	74	4D	74	74
103	51	7A	51	7A	7A
104	53	71	53	71	71
105	4A	7B	4A	7B	84
106	4E	79	4E	79	7C
108	E01C	E05A	E01C	E05A	79
110	01	76	01	76	08
112	3B	05	3B	05	07
113	3C	06	3C	06	0F
114	3D	04	3D	04	17
115	3E	0C	3E	0C	1F
116	3F	03	3F	03	27
117	40	0B	40	0B	2F
118	41	83	41	83	37
119	42	0A	42	0A	3F
120	43	01	43	01	47
121	44	09	44	09	4F
122	57	78	57	78	56
123	58	07	58	07	5E
124	E02AE037	E012E07C	E02AE037	E012E07C	57
125	46	7E	46	7E	5F
126	E11D45E1 9DC5	1477F014 F077	E11D45E1 9DC5	E11477E1 F014F077	62

Windows 95 Update

When the 'Windows 95' operating system was introduced three new keys were added to the PC keyboard. These keys have been retained for all subsequent operating systems and PCs. They are the two 'Flying Windows' keys and the 'Pop Up Menu' key. These keys may be emulated by The Mule in Scancode Mode just like any other key. The appropriate 'make' and 'break' scancodes are shown below...

	Make	Break
Left Flying Window	E0 1F	E0 F0 1F
Right Flying Window	E0 27	E0 F0 27
Pop Up Menu	E0 2F	E0 F0 2F

January 2003 Update

Some computers are appearing with 3 extra Power Management keys. These keys are used to support OnNow architecture PCs. (OnNow is a term for a PC that is always on but appears off and responds immediately to user or other requests.) The three keys are Power, Sleep and Wakeup. These keys are non repeating keys. In other words the 'Make' scancode is sent once regardless of how long the key is held down. These keys may be emulated by The Mule in Scancode Mode just like any other key. The appropriate 'make' and 'break' scancodes are listed below...

	Make	Break
Power	E0 37	E0 F0 37
Sleep	E0 3F	E0 F0 3F
Wake Up	E0 5E	E0 F0 5E

Altek Instruments have designed and built a general purpose, low cost PC interface which generates Keyboard Scancodes. Any key or combination of keys may be emulated thus enabling any applications program to interact with RS232 peripheral devices. We call it The Mule™.

Altek Instruments Ltd have a range of products designed for the data collection/automatic ID industries.



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