Can, could, and be able to are all used to talk about a person's ability to do something. You use can or be able to to talk about ability in the present. Be able to is more formal than can. You can all read and write.

Is Can able grammatically correct?

Be able to is possible in all tenses - but "can" is possible only in the present and "could" is possible only in the past for ability. ... So we use be able to when we want to use other tenses or the infinitive.

What is the difference between can and be able to?

'Can' is a modal auxiliary verb that expresses general ability in the present tense; 'could' works the same way, but in the past tense. 'To be able to' is not a modal auxiliary verb. It is the conjugated verb 'to be' + the adverb 'able' + the infinitive 'to'.