ASCII Table

What is this for?

ASCII (American Standard Code for Information Interchange) is the 128-character coding system that maps the digits, letters, punctuation, and a handful of control codes onto the integers 0–127. It's the foundation every modern text encoding (UTF-8, Latin-1, Windows-1252) extends, so knowing the values is occasionally vital — diagnosing a stray byte in a binary file, building a regex for "any printable", reading a hex dump, or remembering whether 0x0A or 0x0D is a newline.

When to use it

• Reading a hex dump and trying to figure out what those bytes say.
• Writing a parser and needing the boundary values: 0x20 (space), 0x7E (tilde) — the printable range.
• Debugging a CSV that broke because something contained 0x09 (Tab) or 0x1F (Unit Separator).
• Crafting an HTML entity for a tricky character — A = A.
• Settling an argument about whether \r is 0x0D (yes — Carriage Return) and \n is 0x0A (yes — Line Feed).

Common gotchas

• ASCII is 7-bit, not 8-bit. Codes 128–255 are not ASCII — they belong to whatever 8-bit encoding (Latin-1, CP-1252, …) the document declares, or are the lead bytes of a UTF-8 sequence.
• Newlines differ by platform. Unix/macOS use LF (0x0A) only; legacy Mac Classic used CR (0x0D); Windows uses CRLF. Files that mix them break naïve line counting.
• Control characters can be invisible saboteurs. A copy/paste from a terminal or PDF can pick up 0x1F, 0x07 (BEL — actually beeps the terminal), or zero-width Unicode characters that aren't ASCII at all. If text "looks fine" but compares unequal, dump it to bytes.
• HTML entities aren't always needed. In modern UTF-8 documents, A and the literal A are equivalent. Only escape characters that have syntactic meaning in HTML: &, <, >, and " in attributes.
• NUL (0x00) terminates strings in C. Don't embed it in C-string buffers without thinking — many APIs will silently truncate at the first NUL.