efaq: Basic keys
1.1 What do these mean: ‘C-h’, ‘C-M-a’, <RET>, ‘<ESC> a’, etc.?
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• ‘C-x’: press the <x> key while holding down the <Control> key
• ‘M-x’: press the <x> key while holding down the <Meta> key (if your
computer doesn’t have a <Meta> key, 
No Meta key)
• ‘M-C-x’: press the <x> key while holding down both <Control> and
<Meta>
• ‘C-M-x’: a synonym for the above
• <LFD>: Linefeed or Newline; same as ‘C-j’
• <RET>: <Return>, sometimes marked <Enter>; same as ‘C-m’
• <DEL>: <Delete>, usually *not* the same as <Backspace>; same as
‘C-?’ (see Backspace invokes help, if deleting invokes
Emacs help)
• <ESC>: Escape; same as ‘C-[’
• <TAB>: Tab; same as ‘C-i’
• <SPC>: Space bar
Key sequences longer than one key (and some single-key sequences) are
written inside quotes or on lines by themselves, like this:
‘M-x frobnicate-while-foo RET’
Any real spaces in such a key sequence should be ignored; only <SPC>
really means press the space key.
The ASCII code sent by ‘C-x’ (except for ‘C-?’) is the value that
would be sent by pressing just <x> minus 96 (or 64 for upper-case <X>)
and will be from 0 to 31. On Unix and GNU/Linux terminals, the ASCII
code sent by ‘M-x’ is the sum of 128 and the ASCII code that would be
sent by pressing just <x>. Essentially, <Control> turns off bits 5 and
6 and <Meta> turns on bit 7(1).
‘C-?’ (aka <DEL>) is ASCII code 127. It is a misnomer to call ‘C-?’
a “control” key, since 127 has both bits 5 and 6 turned ON. Also, on
very few keyboards does ‘C-?’ generate ASCII code 127.
(emacs)Keys.
---------- Footnotes ----------
(1) DOS and Windows terminals don’t set bit 7 when the <Meta> key is
pressed.
Info Catalog
efaq: FAQ notation
efaq: Extended commands