Should / ought to

	meaning	use	present	past
1.	advice (giving/asking for)	+ /? / -	Should these commands be carried out?	-
2.	obligation	+ / -	The files ought to be fully defined.	The PC shouldn’t have been used inappropriately.
3.	possibility	+	You should see the message on the screen.	They should have carried out the calculations.
4.	complaint	+ / -	You should be using another application for this purpose.	These devices should have been handled with great care.

Note:

Should/Ought to have no other forms. To express past perfect infinitive can be used sometimes.

Упражнение 4. Прочтите и переведите следующие предложения, обращая внимание на значение модальных глаголов should/ought to и форму инфинитива после них:

1. It determines which operations should be carried out and in what order. 2. They ought to have tested new applications. 3. Make sure your last command is finished. You should see the prompt on the screen. 4. The batteries should not be kept uncharged. 5. What kind of data ought to be typed?

NEED

	meaning	use	present	past
1.	necessity	+	To do this, you need to understand how the data bus width affects performance.	He needed to back up that file regulary.
2.	no obligation	-	You don’t need to use virus scanning every time.	You didn’t need to back up these files.

Notes:

1. Need can be used in different forms with and without “to” after it.

2. Needn’t and don’t need to are different.

- We generally use needn’t when the authority comes from the speaker and don’t need to when the authority doesn’t come from the speaker.

- To talk about the past, we use needn’t and Perfect Infinitive (means: you did but it wasn’t necessary) or didn’t need to.

Упражнение 5. Прочтите и переведите следующие предложения, обращая внимание на значение модального глагола need и форму инфинитива после него:

1. Most memory chips are now mounted on boards, you needn’t have checked for other ports. 2. Nonvolatile media are needed to store programs and data when the power is off. 3. The smaller size reduced the distance electrical signals needed to travel. 4. The fields need not be contiguous in memory, nor do they need to be part of a structure. 5. You can insert the executable code you need to “clean up” at an embed point.