ASCII Keyboard Reference

Every key on a standard US keyboard maps to one or two ASCII values depending on whether Shift is held. Pressing the A key sends ASCII 97 (lowercase a). Hold Shift and it sends 65 (uppercase A). The difference between any uppercase and lowercase letter is always exactly 32, a single bit flip at position 5 in the binary representation. This was a deliberate hardware optimization from the 1963 ASA committee.

The keyboard itself does not generate ASCII codes. It sends scancodes that identify the physical key position. Scancode 0x1E fires whether your layout is QWERTY, AZERTY, or Dvorak. The operating system's keyboard driver translates scancodes into character codes based on the active layout and modifier state.

The Ctrl key works by clearing bits 5 and 6 of the character code, mapping letters tocontrol characters 0 through 31. Ctrl+A produces SOH (1), Ctrl+Z produces SUB (26). This bitmask trick is why the 26 Ctrl+letter combinations map directly to the first 26 control characters.

Letter Keys (A-Z)

Each letter key produces two ASCII values. Lowercase occupies positions 97-122, uppercase 65-90. Toggle case by adding or subtracting 32. In binary, bit 5 (value 32) is the only difference betweenA (1000001) anda (1100001).

Key	Upper	Dec	Hex	Lower	Dec	Hex
A / a	A	65	0x41	a	97	0x61
B / b	B	66	0x42	b	98	0x62
C / c	C	67	0x43	c	99	0x63
D / d	D	68	0x44	d	100	0x64
E / e	E	69	0x45	e	101	0x65
F / f	F	70	0x46	f	102	0x66
G / g	G	71	0x47	g	103	0x67
H / h	H	72	0x48	h	104	0x68
I / i	I	73	0x49	i	105	0x69
J / j	J	74	0x4A	j	106	0x6A
K / k	K	75	0x4B	k	107	0x6B
L / l	L	76	0x4C	l	108	0x6C
M / m	M	77	0x4D	m	109	0x6D
N / n	N	78	0x4E	n	110	0x6E
O / o	O	79	0x4F	o	111	0x6F
P / p	P	80	0x50	p	112	0x70
Q / q	Q	81	0x51	q	113	0x71
R / r	R	82	0x52	r	114	0x72
S / s	S	83	0x53	s	115	0x73
T / t	T	84	0x54	t	116	0x74
U / u	U	85	0x55	u	117	0x75
V / v	V	86	0x56	v	118	0x76
W / w	W	87	0x57	w	119	0x77
X / x	X	88	0x58	x	120	0x78
Y / y	Y	89	0x59	y	121	0x79
Z / z	Z	90	0x5A	z	122	0x7A

Digit Keys and Their Shifted Symbols

Digits 0-9 occupy ASCII positions 48-57. Subtract 48 from any digit's ASCII code to get its numeric value. Each digit key also produces a symbol when Shift is held. This mapping is specific to the US QWERTY layout. UK keyboards put the double quote on Shift+2 instead of @.

Key	Normal	Dec	Hex	Shifted	Dec	Hex
0 / )	0	48	0x30	)	41	0x29
1 / !	1	49	0x31	!	33	0x21
2 / @	2	50	0x32	@	64	0x40
3 / #	3	51	0x33	#	35	0x23
4 / $	4	52	0x34	$	36	0x24
5 / %	5	53	0x35	%	37	0x25
6 / ^	6	54	0x36	^	94	0x5E
7 / &	7	55	0x37	&	38	0x26
8 / *	8	56	0x38	*	42	0x2A
9 / (	9	57	0x39	(	40	0x28

Punctuation and Symbol Keys

The remaining punctuation keyseach produce two ASCII characters. Brackets, braces, backslash, semicolon, quotes, and the comma/period/slash cluster all follow the same normal/shifted pattern.

Key	Normal	Dec	Hex	Shifted	Dec	Hex
` / ~	`	96	0x60	~	126	0x7E
- / _	-	45	0x2D	_	95	0x5F
= / +	=	61	0x3D	+	43	0x2B
[ / {	[	91	0x5B	{	123	0x7B
] / }	]	93	0x5D	}	125	0x7D
\ / \|	\	92	0x5C	\|	124	0x7C
; / :	;	59	0x3B	:	58	0x3A
' / "	'	39	0x27	"	34	0x22
, / <	,	44	0x2C	<	60	0x3C
. / >	.	46	0x2E	>	62	0x3E
/ / ?	/	47	0x2F	?	63	0x3F

Whitespace Keys

Three keyboard keys produce whitespace characters. Space (32)is the only one with a visible gap on screen. Tab (9) advances to the next tab stop. Enter produces either CR, LF, or CR+LF depending on the platform and terminal mode.

Key	ASCII Name	Dec	Hex
Space	SP (Space)	32	0x20
Tab	HT (Horizontal Tab)	9	0x09
Enter	CR (Carriage Return)	13	0x0D
Enter (Unix)	LF (Line Feed)	10	0x0A

Ctrl Key Combinations

Holding Ctrl while pressing a key clears bits 5 and 6 of the ASCII value. This maps Ctrl+A through Ctrl+Z to control characters 1 through 26. Several of these have modern terminal functions: Ctrl+C sends SIGINT (interrupt), Ctrl+D sends EOF, Ctrl+Z sends SIGTSTP (suspend). The rest are mostly vestigial teletype codes.

Combination	Dec	Hex	Name	Function
Ctrl+@	0	0x00	NUL	Null character, C string terminator
Ctrl+A	1	0x01	SOH	Start of Heading
Ctrl+B	2	0x02	STX	Start of Text
Ctrl+C	3	0x03	ETX	End of Text / terminal interrupt (SIGINT)
Ctrl+D	4	0x04	EOT	End of Transmission / Unix EOF
Ctrl+E	5	0x05	ENQ	Enquiry
Ctrl+F	6	0x06	ACK	Acknowledge
Ctrl+G	7	0x07	BEL	Bell / terminal beep (\a)
Ctrl+H	8	0x08	BS	Backspace
Ctrl+I	9	0x09	HT	Horizontal Tab (same as Tab key)
Ctrl+J	10	0x0A	LF	Line Feed / Unix newline
Ctrl+K	11	0x0B	VT	Vertical Tab
Ctrl+L	12	0x0C	FF	Form Feed / clear terminal screen
Ctrl+M	13	0x0D	CR	Carriage Return (same as Enter)
Ctrl+N	14	0x0E	SO	Shift Out
Ctrl+O	15	0x0F	SI	Shift In
Ctrl+P	16	0x10	DLE	Data Link Escape
Ctrl+Q	17	0x11	DC1	XON / resume serial transmission
Ctrl+R	18	0x12	DC2	Device Control 2
Ctrl+S	19	0x13	DC3	XOFF / pause serial transmission
Ctrl+T	20	0x14	DC4	Device Control 4
Ctrl+U	21	0x15	NAK	Negative Acknowledge
Ctrl+V	22	0x16	SYN	Synchronous Idle / terminal literal next
Ctrl+W	23	0x17	ETB	End of Transmission Block
Ctrl+X	24	0x18	CAN	Cancel
Ctrl+Y	25	0x19	EM	End of Medium
Ctrl+Z	26	0x1A	SUB	Substitute / Unix suspend (SIGTSTP)
Ctrl+[	27	0x1B	ESC	Escape (same as Esc key)
Ctrl+\	28	0x1C	FS	File Separator / terminal quit (SIGQUIT)
Ctrl+]	29	0x1D	GS	Group Separator / telnet escape
Ctrl+^	30	0x1E	RS	Record Separator
Ctrl+_	31	0x1F	US	Unit Separator

Special Keys

These keys produce ASCII control characters but have dedicated physical keys rather than requiring the Ctrl modifier. Backspace and Delete are frequently confused because terminal emulators map them inconsistently. Check your terminal's configuration if pressing Backspace produces ^? instead of erasing the character.

Key	Dec	Hex	Name	Note
Backspace	8	0x08	BS	Some terminals send DEL (127) instead
Delete	127	0x7F	DEL	Historically erased paper tape by punching all 7 bits
Escape	27	0x1B	ESC	Starts ANSI escape sequences for terminal formatting
Tab	9	0x09	HT	Advances cursor to the next tab stop (every 8 columns)

Keys That Send Escape Sequences

Arrow keys, function keys, Home, End, and other navigation keys have no single ASCII code. Instead, they send multi-byte ANSI escape sequences based on the VT100 terminal standard (DEC, 1978). Every sequence starts with ESC (27), followed by one or more ASCII bytes that identify the key.

Key	Sequence	Decimal Bytes	Hex Bytes
Up Arrow	ESC [ A	27 91 65	1B 5B 41
Down Arrow	ESC [ B	27 91 66	1B 5B 42
Right Arrow	ESC [ C	27 91 67	1B 5B 43
Left Arrow	ESC [ D	27 91 68	1B 5B 44
Home	ESC [ H	27 91 72	1B 5B 48
End	ESC [ F	27 91 70	1B 5B 46
Insert	ESC [ 2 ~	27 91 50 126	1B 5B 32 7E
Page Up	ESC [ 5 ~	27 91 53 126	1B 5B 35 7E
Page Down	ESC [ 6 ~	27 91 54 126	1B 5B 36 7E
F1	ESC O P	27 79 80	1B 4F 50
F2	ESC O Q	27 79 81	1B 4F 51
F3	ESC O R	27 79 82	1B 4F 52
F4	ESC O S	27 79 83	1B 4F 53
F5	ESC [ 1 5 ~	27 91 49 53 126	1B 5B 31 35 7E
F12	ESC [ 2 4 ~	27 91 50 52 126	1B 5B 32 34 7E

Platform Differences

The same physical key can produce different ASCII codes depending on the operating system and terminal configuration. These differences cause real bugs, especially with line endings and the Backspace/Delete confusion.

Key	Windows	macOS	Linux
Enter	CR+LF (13, 10)	LF (10)	LF (10)
Backspace	BS (8)	DEL (127)	DEL (127) or BS (8)
Delete	ESC [ 3 ~	ESC [ 3 ~	ESC [ 3 ~
Ctrl+Z	SUB (26) / EOF marker	SUB (26) / SIGTSTP	SUB (26) / SIGTSTP
Special chars	ALT codes via numpad	Option key combinations	Compose key sequences

On Windows, ALT codes let you type any character from the active code page by holding ALT and typing the decimal value on the numeric keypad. ALT+65 produces A, ALT+130 produces the accented e fromCode Page 437. Adding a leading zero (ALT+0233) uses the Windows-1252code page instead.

Keys With No ASCII Representation

Several keyboard keys exist entirely outside the ASCII character set. They produce hardware scancodes or OS-level keycodes but never generate an ASCII byte. Applications that read raw ASCII input (like serial terminal programs) cannot detect these keys at all.

Key	What It Sends	Used By
Windows / Super	OS-level keycode only	Start menu, window management shortcuts
Command (Mac)	OS-level keycode only	Application shortcuts (Cmd+C, Cmd+V)
Alt / Option	Modifier flag, no ASCII output alone	Menu access (Windows), special chars (Mac)
Caps Lock	Scancode toggle, no ASCII output	Shifts letter case state persistently
Num Lock	Scancode toggle, no ASCII output	Switches numpad between numbers and navigation
Scroll Lock	Scancode toggle, no ASCII output	Legacy terminal scrollback, largely unused
Print Screen	OS-level event only	Screenshot capture
Pause / Break	Scancode only (E1 1D 45)	Debugging, legacy DOS pause
Volume / Media keys	HID usage codes via USB	OS media controls, not visible to applications

Frequently Asked Questions

What ASCII code does the Enter key send?

It depends on the platform. On macOS and Linux, Enter sends LF (line feed, decimal 10). On Windows, Enter sends CR followed by LF (decimal 13 then 10). In raw terminal mode on Unix, Enter sends CR (decimal 13) and the terminal driver translates it to LF. Serial terminals historically sent CR only. This inconsistency dates back to the 1960s when teletypes needed both a carriage return (move the print head left) and a line feed (advance the paper) as separate mechanical operations.

Why do Ctrl+C and Ctrl+V have ASCII codes but no visible characters?

Ctrl+C produces ETX (End of Text, decimal 3) and Ctrl+V produces SYN (Synchronous Idle, decimal 22). These are control characters from the original 1963 ASCII standard, designed for teletype communication. The copy/paste shortcuts came decades later when graphical operating systems repurposed Ctrl combinations for application commands. The terminal still receives the original ASCII control code. That is why pressing Ctrl+C in a terminal sends SIGINT (interrupt signal) instead of copying text - the terminal interprets ETX as an interrupt before any application sees it.

How do arrow keys work if they have no ASCII code?

Arrow keys send multi-byte ANSI escape sequences, not single ASCII values. Pressing the up arrow sends three bytes: ESC (27), then the bracket character [ (91), then the letter A (65). Down is ESC [ B, right is ESC [ C, left is ESC [ D. The terminal emulator generates these sequences based on the VT100 standard from 1978. Function keys work the same way but with longer sequences. Programs like vim and bash parse these byte sequences to detect which key was pressed.

What is the difference between a scancode and an ASCII code?

A scancode identifies the physical key position on the keyboard. ASCII codes represent characters. When you press the A key, the keyboard controller sends scancode 0x1E to the computer. The operating system then translates that scancode into ASCII 65 (uppercase A) or 97 (lowercase a) depending on Shift and Caps Lock state. Scancodes are hardware-level and layout-dependent. The same physical key sends the same scancode regardless of whether your layout is QWERTY, AZERTY, or Dvorak. The OS keyboard driver handles the mapping from scancode to character code.

Related Resources

ASCII Table ALT Codes Control Characters Text to ASCII Converter Control Characters Guide EBCDIC Table