CAN - be able to do smth. / Be capable of doing smth.

  1. MAY - to be allowed (permitted) to do smth.
  2. Now after your teaching practice you have some first-hand experience which you may use doing the tasks below.
meaning use present past
1. physical or mental ability or possibility + -? You can use computer for various purposes. We could not use the floppy because of the viruses.
2. permission + You can try a new application for this task. -
3. suggestions + We can / could try another procedure instead. -
4. offer ? Can I offer you this new product of IBM? -
5. polite request ? Can / Could you help me with the database? -
6. surprise or astonishment ? Can / Could you make such an inquiry? How can / could you have entered this data?
7. doubt or uncertainty - - The processor can not / could not have come to a halt.
8. certainty - They can not / could not be They can not / could not have been
9. prohibition - We can not get access. They could not use that devise.
10. lost opportunity or complaint + - The floppy could at least have been checked for viruses before.


1. Canhas only two tense forms: can(Present) and could(Past), so for other tenses to be able to do smth.or to be capable of doing smth.are used. But if you mean that someone managed to do something in one particular situation (where can or could are possible), you have to use was / were able to do smth.or was / were capable of doing smth.

2. Couldis not always the past of can, Sometimes it has a present or future meaning. Perfect infinitive after canor couldin such cases shows that they refer to the past.

3. Passive and progressive infinitives after canor couldare also possible in some cases.

1. , 䳺can :

1. You can end your program with 'quit' command. 2. The information from memory can be retrieved by CPU. 3. We will be able to correct the arrows in the program. 4. Could not the transistors or other radio elements be joined together right inside the crystal? 5. Engineers could thus substitute program code words for hardware parts. 6. Could not they have created this program by themselves? 7. The computer memory can be considered as consisting of a number of cells capable of storing binary patterns representing program instructions or data. 8. He was not able to perform those calculations without a computer. 9. In one program run, memory cells 5 and 6 could have been set to 70 and 25, respectively. 10. The sequence could not have been chosen wrongly.

II. | MAY - to be allowed (permitted) to do smth.

| | | | II. | III. | SHOULD / OUGHT TO | HAVE TO | WILL / WOULD | Design for Decision |

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