Quora: How do Vietnamese people type Vietnamese letters?

There is indeed a Vietnamese keyboard layout that is included in all modern operating systems since Windows 2000 (I don't know the exact time when it was included in other OSes though). It's no different from US QWERTY layout except:

• Vietnamese-specific keys added in number/symbol key positions
• The keys' function swapped between typing characters and numbers/symbols.

There are also useless characters like cedilla Ç and OE ligature Œ that most Vietnamese people won’t have a clue what those are for.

So that means you can type Vietnamese without any 3ʳᵈ party software, although a bit uncomfortable.

However most people don't know this or consider this layout stupid because you cannot write the numbers and normal symbols like !@#$%^&... directly but you must type them with the AltGr modifier. There is no keyboard produced based on this layout either, so nobody uses this. Instead they use normal US QWERTY keyboards and VNI and Telex input method with some input method software (most commonly Unikey which replaced Vietkey) like others have said.

There are some other alternatives like WinVNKey and GoTiengViet by Trần Kỳ Nam. Earlier, people would used Vietkey in Windows and Vietres in DOS. In other operating systems there are other software packages such as xunikey and iBus in Linux.

VNI is more common in the South because most (if not all) teachers in the South teach it to their students. Telex is more prevalent in the North but some Southerners, after learning VNI in schools, try Telex themselves and choose to switch to it because it makes typing faster, especially when typing with ten fingers.

In fact I've seen several Mitsumi keyboards labelled "Vietnamese keyboard layout" on the box but they were not following this layout.

In prior versions of Windows Phone, Microsoft also used this layout and received a lot of criticism since it took so much valuable screen space and was hard to type with since nobody was accustomed to it. Therefore they had to create two more keyboard layouts using the common VNI and Telex typing methods.

A new input method using VNI and Telex for Windows codenamed BlackCi (BLACK Ci) supported and distributed by Microsoft is also being released in various technology forums for public experiment. It was intended to be the official Vietnamese input method to be included in windows 8 but for some reason they aren't finished yet.

In older times Vietnamese typewriters were actually produced using two different keyboard layouts. One of them is like this:

The other layout is very different than the QWERTY. I tried hard but cannot find it.

I was fortunate to have the luck of learning how to use typewriters and I wonder why one of those layouts isn't the official layout for Vietnamese keyboards. It would make typing Vietnamese faster. I don't know who invented the current Vietnamese keyboard layout used in computer OSes mentioned in the beginning of this answer but it's really silly and ridiculous while VNI and Telex make some characters three strokes to type and that's undesirable.

EDIT:
I think I have found the other Vietnamese keyboard layout for typewriters:

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On Google Translate you can set the source language to Vietnamese, which will then show you a button [ ê ] to select an input method. Select TELEX (which is probably the most commonly used).

Once you have selected it, you can type something in Vietnamese using the TELEX rules (the mapping of keys to diacritics has been mentioned in other answers).

An example: type

nuowcs Vieetj Nam, ddoocj laapj - tuwj do - hanhj phucs

to get

(meaning “country of Vietnam, independence - freedom - happiness”, the official motto of VN)