ASCII Control Codes Table

The standard 7-bit ASCII character set has 128 code positions. Decimal codes 0–31 are control characters, and code 127 is DEL. These entries generally do not represent ordinary printable letters or symbols.

Important: Control codes may affect text layout or communication protocols rather than displaying a visible symbol. Their exact behavior depends on the software, terminal, device or protocol.
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Showing 33 of 33 reference entries.

Decimal Hex Binary Abbreviation Character name Description Copy
0 00 0000000 NUL Null Null character; historically used for padding or indicating an empty value.
1 01 0000001 SOH Start of Heading Marks the beginning of a heading or control information in certain protocols.
2 02 0000010 STX Start of Text Marks the beginning of text in some communication protocols.
3 03 0000011 ETX End of Text Marks the end of a text section in some communication protocols.
4 04 0000100 EOT End of Transmission Indicates the end of a transmission in certain protocols.
5 05 0000101 ENQ Enquiry Requests a response or status from another device or system.
6 06 0000110 ACK Acknowledge Indicates that data or a message has been received successfully.
7 07 0000111 BEL Bell Historically signals an audible or visual alert.
8 08 0001000 BS Backspace Moves the printing position backward by one position in applicable environments.
9 09 0001001 HT Horizontal Tab Advances to the next horizontal tab position. Commonly represented by a tab character.
10 0A 0001010 LF Line Feed Moves to the next line. Commonly used in Unix and Linux line endings.
11 0B 0001011 VT Vertical Tab Advances to the next vertical tab position. Rarely used in modern text.
12 0C 0001100 FF Form Feed Historically advances to the next page or form.
13 0D 0001101 CR Carriage Return Returns the printing position to the start of a line. Used in Windows CRLF line endings together with LF.
14 0E 0001110 SO Shift Out Signals a shift to an alternate character interpretation in systems that support it.
15 0F 0001111 SI Shift In Signals a return to the standard character interpretation in systems that support it.
16 10 0010000 DLE Data Link Escape Changes the interpretation of following characters in certain data communication protocols.
17 11 0010001 DC1 Device Control 1 Device-control character traditionally associated with XON in some serial communication systems.
18 12 0010010 DC2 Device Control 2 Device-control character reserved for device-specific functions.
19 13 0010011 DC3 Device Control 3 Device-control character traditionally associated with XOFF in some serial communication systems.
20 14 0010100 DC4 Device Control 4 Device-control character reserved for device-specific functions.
21 15 0010101 NAK Negative Acknowledge Indicates that data was not accepted or that an error was detected.
22 16 0010110 SYN Synchronous Idle Used by some synchronous communication systems to maintain synchronization.
23 17 0010111 ETB End of Transmission Block Marks the end of a block of data in certain communication protocols.
24 18 0011000 CAN Cancel Indicates that data or an operation should be canceled or disregarded.
25 19 0011001 EM End of Medium Historically indicates the physical end of a medium or the end of usable data.
26 1A 0011010 SUB Substitute Used as a substitute for a character that is invalid, missing, or in error in certain contexts.
27 1B 0011011 ESC Escape Introduces an escape sequence or changes the interpretation of following characters in many systems.
28 1C 0011100 FS File Separator A hierarchical information separator intended for separating files or larger data units.
29 1D 0011101 GS Group Separator An information separator intended for separating groups of records.
30 1E 0011110 RS Record Separator An information separator intended for separating records.
31 1F 0011111 US Unit Separator An information separator intended for separating smaller data units.
127 7F 1111111 DEL Delete Historically associated with deleting or obliterating a character on punched tape. DEL is not strictly a control character under the original RFC 20 terminology.
No ASCII control codes match your search. Try another abbreviation, name, decimal value or hexadecimal value.

Binary values are shown as 7-bit ASCII representations, including leading zeros. Hexadecimal values use two digits for convenient reference.

What Are ASCII Control Characters?

ASCII stands for American Standard Code for Information Interchange. The original 7-bit ASCII encoding assigns numeric values from 0 through 127 to characters and control functions. Control characters were designed to help manage communication, text formatting and device behavior.

Many control characters do not have a visible glyph. For example, line feed (LF, decimal 10) moves text to a new line in many environments, while horizontal tab (HT, decimal 9) represents a tabulation character. Other codes originated in older communication systems and may have little or no effect in a modern application.

ASCII code ranges

  • 0–31: ASCII control characters.
  • 32: Space, a printable character that normally appears as a blank.
  • 33–126: Printable ASCII punctuation, digits, uppercase and lowercase letters, and symbols.
  • 127: DEL, traditionally associated with deleting or obliterating a character.

Although DEL is commonly included in ASCII control-code tables, RFC 20 notes that it is not strictly a control character in the same sense as codes 0–31.

Important ASCII Control Characters

NUL — Null (Decimal 0, Hex 00)

NUL is the zero-valued ASCII character. It has historical uses in padding and data representation. In programming, a NUL byte is not the same thing as the printable two-character string \0; the latter is a common notation used in source code to represent the byte.

HT — Horizontal Tab (Decimal 9, Hex 09)

HT represents horizontal tabulation. In source code, strings and text files it is often represented by \t. The visual width of a tab depends on the application and its tab-stop settings.

LF — Line Feed (Decimal 10, Hex 0A)

LF is commonly used as a newline character in Unix and Linux text files. It is often written as \n in programming languages. The exact handling depends on the language and operating environment.

CR — Carriage Return (Decimal 13, Hex 0D)

CR represents a carriage return. Windows text files conventionally use CR followed by LF (CRLF) as a line ending, while Unix-like systems typically use LF alone. CR and LF are distinct characters.

ESC — Escape (Decimal 27, Hex 1B)

ESC can introduce escape sequences. In terminals, these sequences may control cursor movement, text styling or other terminal behavior. ESC itself is a control code; the bytes that follow determine the sequence's meaning.

DEL — Delete (Decimal 127, Hex 7F)

DEL was associated with erasing or obliterating unwanted characters in punched-tape systems. In modern contexts, its meaning depends on the application, terminal, protocol or input-handling convention.

Decimal, Hexadecimal and Binary Representations

The same ASCII code can be expressed in different number systems. Decimal is convenient for counting, hexadecimal is compact for debugging and byte-oriented data, and binary shows the individual bits.

Character Decimal Hexadecimal 7-bit binary Common notation
NUL 0 00 0000000 \0 in some languages
HT 9 09 0001001 \t
LF 10 0A 0001010 \n
CR 13 0D 0001101 \r
ESC 27 1B 0011011 Escape character
DEL 127 7F 1111111 Delete

A hexadecimal byte is conventionally written using two hex digits, such as 0A. Standard ASCII itself uses seven bits; a byte-oriented system often stores an ASCII value in an eight-bit byte with the high bit set to zero.

Frequently Asked Questions

1. How many ASCII control characters are there?

The traditional reference includes 33 entries: decimal codes 0–31 and code 127 (DEL). Strictly speaking, RFC 20 distinguishes DEL from the control characters 0–31.

2. What is the ASCII code for a newline?

Line feed (LF) is decimal 10 and hexadecimal 0A. Carriage return (CR) is decimal 13 and hexadecimal 0D. Some systems use LF alone; Windows text files conventionally use CR followed by LF.

3. What is the difference between CR and LF?

CR means carriage return and traditionally moves the position to the beginning of a line. LF means line feed and moves to the next line. They are different ASCII codes and may be combined in CRLF line endings.

4. What is the ASCII code for ESC?

ESC (Escape) is decimal 27, hexadecimal 1B, and seven-bit binary 0011011. It is commonly used to introduce escape sequences in terminals and communication systems.

5. Why do control characters not display normally?

They were designed mainly to represent control functions rather than visible letters or symbols. A program may interpret them, ignore them, display a placeholder, or show a special notation.

6. Is ASCII the same as UTF-8?

No. ASCII is a 7-bit character encoding. UTF-8 is a variable-length Unicode encoding whose first 128 code points use the same byte values as ASCII. UTF-8 can also represent many characters beyond the ASCII range.

7. How can I copy an ASCII control code?

Search or filter the reference table, then click Copy beside the desired entry. The copied value includes its decimal number, abbreviation, name, hexadecimal representation and binary value.

Related Binary and Number System Tools

Explore these related tools on Binarios.org for converting and understanding binary data and digital representations.

Further Reading

The original ASCII network-interchange reference documents the standard character table and describes the historical functions of its control codes.

RFC 20 — ASCII Format for Network Interchange