Questions

If some action has started in the past and is still continuing, then present perfect continuous tense should be used instead of present continuous tense. So, the phrase ‘am waiting’ needs to be replaced with ‘have been waiting’ to make the sentence contextually correct. Thus, the correct formation would be, ‘I have been waiting for three –quarters of an hour’.

The main function of input devices is to direct commands and data into computers. Computers then use their CPU to process this data and produce output.

Examples of input devices - keyboards, mouse, barcode readers, Magnetic Ink Character Readers (MICR), Optical Character Readers (OCR), touch screens, etc...

Junk e-mail is also called Spam.

Sending irrelevant messages or the same message to a large number of users over the internet for the purpose of advertisement or malicious intent is called as spamming and that content is called as SPAM or JUNK.