2. What is a register variable?

Register variables are a special case of automatic variables. Automatic variables are allocated storage in the memory of the computer.

Register variables are a special case of automatic variables. Automatic variables are allocated storage in the memory of the computer; however, for most computers, accessing data in memory is considerably slower than processing in the CPU. These computers often have small amounts of storage within the CPU itself where data can be stored and accessed quickly. These storage cells are called registers.