Mixed and Absolute Cell References. To avoid this problem created by the relative cell reference A7, mixed and absolute cell references can be used, which prevent all or part of a cell reference in a formula from changing as it is copied. Absolute and mixed cell references are created by adding dollar signs ($) to a cell reference. For example, in the image above, the cell reference $A$6 in the formula in cell B2 is an absolute cell reference and $A2 is a mixed cell reference.
The point of sale (POS) is the time and place where a retail transaction is completed. It is the point at which a customer makes a payment to the merchant in exchange for goods or after provision of a service.
The term 'Point of Sale' (POS) is ambiguous. It can refer to the cash till or payment machine as a whole, or just to the bit that reads the card. Usually, it means the whole cash register, and sometimes includes the human operator as well. There are at least two types of payment card.