Control Characters | ASCII Code Codes

Control characters in ASCII code are those that do not represent a visible symbol on the screen, but are used to control devices, such as printers or text terminals. These characters perform specific functions, such as controlling the position of the cursor, starting a new line, or signaling the end of a file.

ASCII code control character table

Complete list of ASCII commands and control characters ranging from 0 to 31.

Decimal	Octal	Hex	Binary (8 bits)	Symbol / Abbreviation	Representation	Description
0	000	00	0000 0000	NUL	␀	Null character
1	001	01	0000 0001	SOH	␁	Start of Heading
2	002	02	0000 0010	STX	␂	Start of Text
3	003	03	00000011	ETX		End of Text
4	004	04	00000100	EOT		End of Transmission
5	005	05	00000101	ENQ		Enquiry
6	006	06	00000110	ACK		Acknowledge
7	007	07	00000111	BEL		Bell, Alert
8	010	08	00001000	BS		Backspace
9	011	09	00001001	HT		Horizontal Tab
10	012	0A	00001010	LF		Line Feed
11	013	0B	00001011	VT		Vertical Tabulation
12	014	0C	00001100	FF		Form Feed
13	015	0D	00001101	CR		Carriage Return
14	016	0E	00001110	SO		Shift Out
15	017	0F	00001111	SI		Shift In
16	020	10	00010000	DLE		Data Link Escape
17	021	11	00010001	DC1		Device Control One (XON)
18	022	12	00010010	DC2		Device Control Two
19	023	13	00010011	DC3		Device Control Three (XOFF)
20	024	14	00010100	DC4		Device Control Four
21	025	15	00010101	NAK		Negative Acknowledge
22	026	16	00010110	SYN		Synchronous Idle
23	027	17	00010111	ETB		End of Transmission Block
24	030	18	00011000	CAN		Cancel
25	031	19	00011001	EM		End of medium
26	032	1A	00011010	SUB		Substitute
27	033	1B	00011011	ESC		Escape
28	034	1C	00011100	FS		File Separator
29	035	1D	00011101	GS		Group Separator
30	036	1E	00011110	RS		Record Separator
31	037	1F	00011111	US		Unit Separator
Decimal	Octal	Hex	Binary	Symbol / Abbreviation	Representation	Description

Non-printable control characters from the ASCII code table.

What are control characters?

As I mentioned at the beginning, control characters in the ASCII code are a set of codes that do not represent visible symbols such as letters or numbers, but are used to control the flow of data, the presentation of text, and the operations of devices such as printers or terminals. These characters occupy the first 32 values of the ASCII table (from 0 to 31) plus the value 127, and are essential for communication in old and modern computer systems.

What is the function of control characters?

As the name suggests, these codes are responsible for telling a computer or device to perform an action. Some of the most common functions are:

Line Feed (LF, code 10): Moves the cursor to the next line.
Carriage Return (CR, code 13): Moves the cursor to the beginning of the line, similar to what a typewriter does.
Horizontal Tab (HT, code 9): Advances the cursor to the next tab position.
Delete (DEL, code 127): Deletes a character or line of text.
End of Text (ETX, code 3): Signals the end of a text transmission.

Control characters examples

0 (NULL): Null character, used in many applications to indicate the end of a text string.
7 (BEL): Activates or emits a bell or alert sound on the device (for example, a “beep”).
8 (BS): Backspace, go back one character, like when you delete something.
9 (TAB): Horizontal tabulation.
10 (LF): Line Feed.
13 (CR): Carriage Return.
27 (ESC): Escape character, used to change modes on devices or initiate special sequences.
And character 127 (DEL): It is the “delete” character.

Use in modern systems

Although many of these control characters originated in older systems such as teletypewriters, they are still relevant in modern communication protocols and text file formats. For example, the carriage return and line feed are essential in systems such as Windows and Unix to indicate the end of a line of text.

In short, control characters are instructions that cannot be seen but play a crucial role in the organization, transmission and presentation of text in computer systems.