ASCII 39 — '

The apostrophe (single quote) serves dual roles as a punctuation mark for possession and contraction in English, and as a string delimiter in many programming languages. In SQL, single quotes delimit string literals, and failing to properly escape apostrophes in user input is the root cause of SQL injection — one of the most prevalent and dangerous web security vulnerabilities. In Python and JavaScript, single quotes are interchangeable with double quotes for string literals. In shell scripting, single quotes prevent all variable expansion.

Punctuation marks serve as the structural scaffolding of written language, delineating sentences, clauses, and phrases while conveying emphasis and grouping. In programming, these same characters gain powerful additional roles as operators, statement terminators, delimiters, and syntactic markers that compilers and interpreters rely upon. This dual significance in both natural language and code syntax means punctuation characters carry outsized functional importance relative to their small count in the ASCII character set.

In the ASCII encoding table, Apostrophe is assigned code point 39 in decimal (0x27 hexadecimal, 047 octal, 00100111 binary). The 7-bit ASCII standard, first published in 1963 by the American Standards Association, defines exactly 128 characters that remain the foundation of text encoding systems worldwide. UTF-8, the dominant encoding on the modern web, is fully backward compatible with ASCII — every ASCII character is encoded as the identical single byte in UTF-8, guaranteeing that Apostrophe works reliably across all operating systems, programming languages, and internet protocols.