ASCII 79 — O

The uppercase letter O (ASCII code 79) is the fifteenth letter of the modern Latin alphabet, evolved from the Phoenician ayin (meaning eye) via Greek omicron. In English text, the letter o appears with a frequency of approximately 7.5%, ranking as the 4th most common letter. O is rendered as a perfect circle or oval in most typefaces, a distinctive visual form that has remained remarkably unchanged for thousands of years of writing history.

The 26 uppercase Latin letters span ASCII codes 65 through 90, forming the capital letter block of the character set. Their placement exactly 32 code positions before the corresponding lowercase letters (97–122) was a deliberate engineering decision enabling case conversion through toggling a single bit. Uppercase letters are essential for proper nouns, sentence openings, acronyms, and programming constants. Early computing systems often supported only uppercase characters, making ASCII's inclusion of both cases a forward-looking design choice.

In the ASCII encoding table, Uppercase Letter O is assigned code point 79 in decimal (0x4F hexadecimal, 117 octal, 01001111 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 Uppercase Letter O works reliably across all operating systems, programming languages, and internet protocols.