ASCII/Unicode Table

ASCII (American Standard Code for Information Interchange) is a 7-bit character encoding standard that assigns numeric values (0–127) to 128 characters: 33 control characters and 95 printable characters including letters (A–Z, a–z), digits (0–9), and punctuation. Developed in 1963, ASCII forms the foundation of virtually all modern text encoding standards including UTF-8, which is backward-compatible with ASCII for the first 128 code points.

Control characters are non-printable ASCII codes originally designed to control teletype machines and printers. Key ones include: NUL (0) — null terminator in C strings; TAB (9) — horizontal tab; LF (10) — line feed, used as newline in Unix/Linux; CR (13) — carriage return, used with LF (CRLF) in Windows line endings; ESC (27) — escape, starts ANSI terminal escape sequences; DEL (127) — delete/rubout character.

All four are different number bases representing the same underlying code point. Decimal (base 10) is the familiar integer value. Hexadecimal (base 16, prefixed "0x") is used extensively in programming, color codes, and memory addresses — for example, "A" is 0x41. Octal (base 8, prefixed "0") appears in Unix file permissions and older C string escape sequences (like \101 for "A"). Binary (base 2) shows the actual bit pattern stored in memory.

Frequently referenced ASCII values: Space = 32 (0x20); "0"–"9" = 48–57 (0x30–0x39); "A"–"Z" = 65–90 (0x41–0x5A); "a"–"z" = 97–122 (0x61–0x7A). The difference between uppercase and lowercase is exactly 32 (0x20), which is why toggling bit 5 converts between cases. Digits 0–9 have ASCII values that are 48 more than their face value, so you can convert "5" to integer 5 by subtracting 48.

ASCII is a 7-bit encoding covering only 128 characters — sufficient for English but not for other languages. Unicode is a universal standard that covers over 149,000 characters across all writing systems. UTF-8 is the most common Unicode encoding: it uses 1 byte for ASCII characters (0–127, identical to ASCII) and 2–4 bytes for additional characters. This backward compatibility means any valid ASCII text is also valid UTF-8.

Line endings are control characters. Unix/Linux/macOS uses only LF (Line Feed, ASCII 10, 0x0A) to end lines. Windows uses CRLF (Carriage Return + Line Feed, 0x0D 0x0A). Classic Mac OS used only CR (0x0D). This difference causes the "mixed line endings" issue when text files are transferred between operating systems. In programming, "\n" represents LF and "\r" represents CR.

NUL (ASCII 0, 0x00) is the null character. In C and C++, strings are terminated by a NUL byte — this is called a "null-terminated string" or "C-string." The NUL character has no visual representation. In data transmission protocols, NUL was historically used for padding and synchronization. In binary file formats, NUL bytes appear frequently as padding, separators, or field terminators.

DEL (Delete, ASCII 127, 0x7F) is a control character that was originally used on paper tape to delete characters — punching all holes in a position to create a DEL character effectively erased the previous character. In modern computing, DEL has no standard function on screen, but it appears in terminal emulators where the Delete key may send 0x7F (vs Backspace which sends 0x08). It is the only control character with code 127, sitting just above the printable ASCII range.