How to read the ASCII table
ASCII assigns a unique number to each of 128 characters so that computers can store and exchange text as bytes. Each row in the table above shows the same character in five forms: its decimal value (0–127), its hexadecimal value (0x00–0x7F), its octal value, its 8-bit binary pattern, and the character itself. For control codes (0–31 and 127) the character column shows the standard abbreviation, such as NUL, ESC or DEL, with a short description, because those codes do not print a visible glyph.
The printable range runs from 32 (space) to 126 (~). Within it, the digits 0–9 are 48–57, uppercase A–Z are 65–90, and lowercase a–z are 97–122. A handy pattern: a lowercase letter is always exactly 32 more than its uppercase counterpart, which is why flipping bit 5 (value 32) toggles letter case.
A is decimal 65. In hex that is 0x41, in octal 0o101, and in 8-bit binary 01000001. Add 32 and you reach decimal 97, which is lowercase a (0x61).Reference note: standard ASCII covers only 0–127. Extended ASCII (128–255) is encoding-dependent — code pages such as Latin-1 / ISO-8859-1, Windows-1252 and DOS CP437 map those numbers to different accented letters and symbols — so this tool focuses on the unambiguous 0–127 range.
Frequently asked questions
- What is ASCII?
- ASCII (American Standard Code for Information Interchange) is a character-encoding standard that assigns a number from 0 to 127 to each character. Codes 0–31 and 127 are control characters, 32 is the space, 48–57 are the digits, 65–90 are uppercase letters and 97–122 are lowercase letters.
- What is the ASCII code for the letter A?
- The uppercase letter A has ASCII code 65 in decimal, which is 0x41 in hexadecimal, 0o101 in octal and 01000001 in 8-bit binary. The lowercase a is 32 higher, at decimal 97 (0x61).
- What are ASCII control characters?
- Control characters are the non-printing codes 0–31 plus 127 (DEL). Instead of showing a glyph they signal actions or structure, such as NUL (0), tab HT (9), line feed LF (10), carriage return CR (13) and escape ESC (27). They date from teleprinter and terminal control.
- What is the difference between ASCII and Unicode or UTF-8?
- ASCII defines only 128 characters (0–127). Unicode is a much larger standard covering virtually every writing system, and UTF-8 is a way to encode Unicode in bytes. The first 128 Unicode code points are identical to ASCII, so any plain-ASCII text is also valid UTF-8.
- How many characters are in the ASCII table?
- Standard ASCII has 128 characters, numbered 0 to 127, which fit in 7 bits. Of these, 95 are printable (codes 32–126, including the space) and 33 are control characters (0–31 and 127).
- What is extended ASCII?
- Extended ASCII refers to the codes 128–255 that become available when a full 8-bit byte is used. There is no single standard for them: different code pages (such as Latin-1 / ISO-8859-1, Windows-1252 or DOS code page 437) map those numbers to different accented letters and symbols, so they are encoding-dependent.