ASCII Table

65 in decimal, 0x41 in hex, 101 in octal, 01000001 in binary. Lower-case a is 97 — exactly 32 more, which is one bit, and that is not a coincidence: setting or clearing bit 5 switches case, which is how case conversion was done before anybody needed to think about other alphabets.

They were commands to a teleprinter rather than marks on a page, and about eight of them are still load-bearing. LF and CR end lines, HT is the tab key, ESC begins every terminal escape sequence, BEL still makes terminals beep, and DC3 — Ctrl+S — still pauses output, which is why a terminal sometimes appears to freeze for no reason. The rest are mostly historical, and this table says which are which.

Because on punched tape, 127 is all seven holes. Any other character could be turned into it by punching out the remaining holes, which made it the one code that could reliably overwrite a mistake. There was no way to un-punch a hole, so “delete” had to be the pattern with every bit set.

Not really, and the phrase causes more trouble than it saves. ASCII is a seven-bit standard that ends at 127. Codes 128 to 255 depend entirely on which encoding is in use — 0xE9 is é in Latin-1, a different character in some code pages, and not a whole character at all in UTF-8. This table shows that range as Latin-1 and labels it, rather than implying there is one answer.

On a teleprinter they were two separate motions: CR returned the print head to the left margin, LF rolled the paper up one line. Unix and macOS ended up using LF alone for a newline, Windows kept both as CR LF, and old Macs used CR alone. That disagreement is why a file moved between systems can show every line running together, or gain a ^M at the end of each one.

Yes — paste it in and you get its row. The box also takes a decimal number, 0x hex, \x hex, a U+ code point, 0b binary, 0o octal, an HTML entity like &, an abbreviation like LF, or a name like “carriage return”. It works out which you meant from what you typed, so there is no mode to set.