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### 1.1 What do these mean: `C-h`, `C-M-a`, `RET`, `ESC a`, etc.?

- `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, see 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 71.

`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.

See Keys in The GNU Emacs Manual.

#### Footnotes

### (1)

DOS and Windows terminals don’t set bit 7 when the `Meta` key is pressed.

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