Most word processors and text editors have some automatic features that allow you to simply type a document in (rather like just using a typewriter), and it’ll enhance the document to use better typography. Unfortunately, some of these features can work against you, and you may want to turn some of them off (e.g. some auto-correction features will change what was correct into something that it thinks is correct, but may be wrong). Some of the common things they’ll do are outlined below:
There’s several ways word processors handle automatic corrections:
It could be as you type, alerting you that it didn’t understand something, or it didn't like something that you typed, and it prompts you to fix it (perhaps with some suggestions). Or it could automatically replace some things as you type (often done to correct commonly badly typed words, such as “teh” instead of “the”), without asking you about it.
You can run a checker manually, and it’ll tell you about any problems it finds, or automatically repair them.
It might run one when you save the document.
And there’s many different sorts of things that can be corrected/adjusted/changed:
Common typing errors
Poor typography (typically punctuation, but includes other traditional typography issues—like changing “1st” to look like “1st”, other similar ones like “№”, using the correct ligatures like “æ” instead of “ae”, and replacing crude approximations of symbols like (C) and (TM) with the proper © & ™ glyphs).
Spelling.
Grammar.
Expanding abbreviations.
Capitalisation.
Of course, being able to manually adjust parts of the document is just as important (such as doing a global search and replace to change every instance of some term, to another).
One thing that’s particularly tedious is creating tables of contents, indexes, footnotes, and other references. Not only do they entail a lot of work to build up, but can require a lot maintenance (a reference to something on page 12 is no good if you’ve added more to the document and it’s now moved to page 13). Good DTP software can allow you to mark items in the document to be indexed, perhaps as themselves, or perhaps against some keyword you supply, or grouped with other things that are related. Then, after you’ve finished typing, or after you’ve modified a document, you run a process that generates the indexes for you, based on the current status of the document.
As you type something using dashs, the program may convert the hyphen character (usually the only one available on the average keyboard) into the correct typographical character. It may know where to use the right ones in the right places, or it may rely on you typing them in a specific manner. A common action is for it to replace a double-dash sequence with an em-dash, though it may only do this if you type a blank space as well. Strictly speaking, it’s not normal to put spaces around an em-dash, but it’s probably a lot easier to type it then erase it, than to use the menu to find how to insert an em-dash into the current location. Some software may give you an en-dash if you typed a blank space after the double dashes, or an em-dash if you typed double-dashes, then the following word, then a blank space. You’ll need to read the manuals for your software, or experiment with it, to work out how yours words.
When you type something like 'example' or "example", some word processors will change those simple (and wrong) symbols into traditional “curly” quotes. Usually this works fine, until you need to start an abbreviated word with an apostrophe, then you might find that you get a left-single-quote, which is a mirror image of an apostrophe (this depends if the word processor is smart, and whether it converts characters as you type, or assesses a block of text after you finish typing it—in this case, to see whether you typed a closing quote, before it changes ' marks into ‘ and ’ quotes). Likewise, you can strike similar problems when using those characters in other places (like measurements).
This is something to be careful about, as most aren’t done in a particularly intelligent manner. The context of the surrounding text may not be taken into consideration (generally the meaning of the word and the sentence around it are not considered, nor the grammar, nor the particular language being used—for instance, the American variation of English is not the same as English in other countries).