A DID number is basically a telephone number provided by the service provider, which allows for direct dialling to individuals within an organisation without intervention from a receptionist or auto attendant. These numbers have no unique physical lines and calls cannot be placed on a DID number.
A number is a mathematical object that is used in counting and measuring. Natural numbers are the most familiar numbers this are 0, 1, 2, 3, etc. uk.ask.com
