Text messaging was a fairly new phenomenon when I wrote a Wordplay article about it in April 2002. Now it seems that half the population is sending text messages.

For those unfamiliar with texting, on many phones the keys for each number from two to nine also allow you to key in particular letters of the alphabet: two covers ABC, three covers DEF, and so on.

Thus you can spell out words by pressing the keys the correct number of times (press number two twice for the letter B, three times for the letter C). For instance, you can send the word faced' by pressing 333-2-222-33-3.

As most mobile phones have keys much smaller than people's fingers, it is easy to press the wrong key and send the word death instead of debug, apron instead of arson, oaths instead of maths, carnage instead of barmaid, or boobs instead of bombs.

Different words created by pressing the same keys are commonly called textonyms'. This has given me the idea for a game in which people list as many words as they can produce by pressing a particular set of keys.

For instance, if you press the second, sixth and ninth keys, you can get nine different possibilities: Amy, any, bow, box, boy, cow, cox, coy or coz. You might even look for appropriate sets of such words. For example, pressing 5477 can give you kiss or lips, while 4633 gives you good or home.

Now technology has come up with predictive texting', which supposedly anticipates the words you want to send. When you press a number key once, it predicts the word you intend to send. Thus faced' can be texted by pressing no more than 3-2-2-3-3, which entails half the keystrokes you would have used in the earlier example.

This can theoretically save time but it may actually add to the effort of sending a message. If you want to type the word concert', for example, the most commonly-used text system predicts that you want to say concept and you have to change that word into the one you actually want.

Similarly, predictive texting can turn love into loud and too into two or tom. If you want to tell someone you will meet them in Thame, predictive texting may change Thame into thane.

Predictive texting was anticipated by the spell-checker, which is provided with most computers and ostensibly saves you time by checking how you spell each word. It can certainly help you to avoid such common mistakes as typing hte' when you mean the.

However, it cannot help if you use homonyms, typing of coarse when you mean of course, or diffuse when you mean defuse, as the wrong' words are still acceptable to a spell-checker.

And a spell-checker can introduce errors of its own. Many spell-checkers are American, and instruct you to spell theatre as theater and behaviour as behavior.

When I typed the word cox earlier, the word was highlighted to show that it isn't included in my computer's spell-check dictionary, which offers me the alternative suggestions of Cox (with a capital C), coax, co, cocks and cod.

In a recent television review, I wanted to say that a programme was watchable but the spell-checker would only allow patchable or washable. And they couldn't cope with the French philosopher Diderot, offering instead: Demerit, Desert, Idiot, Deirdre and Diego!

The problems caused by spell-checkers are admirably illustrated in a poem which begins thus: I have a spelling chequer, It came with my Pea Sea.

It plane lee marks four my revue Miss steaks aye can knot sea.

Eye ran this poem threw it, Your sure reel glad two no.

It's vary polished in it's weigh, My chequer tolled me sew.

A chequer is a bless sing, It freeze yew lodes of thyme.

Hit helps me right awl stiles two reed, And aides me when aye rime.

Grammar checkers can also be misleading. A survey showed that a typical grammar checker supplied with a computer only detected 19 out of 67 grammatical errors but labelled many correct sentences as errors.

As with spell-checkers, you have to be careful about weighing up the advice you are given, which sometimes seems unnecessarily finicky (as when grammar checkers advise you to avoid the passive voice on almost every occasion). If I write "A rose by any other name", the grammar checker in my computer wants me to give the quotation in full, instead of assuming that the reader will recognise the reference.

Another possible source of confusion is provided by computer thesauruses, which offer alternatives that some people (especially foreign learners of English) may assume can be substituted directly for another word. The thesaurus on my computer suggests that I could have started this paragraph by saying "Another probable spring" or "Another likely font".

Tony Augarde is the author of The Oxford Guide to Word Games (OUP, £14.99) and The Oxford A to Z of Word Games (OUP, £4.99).