register Variables

The register storage specifier originally applied only to variables of type int, char, or pointer types.
However, in Standard C, register's definition has been broadened so that it can be applied to any
type of variable.
Originally, the register specifier requested that the compiler keep the value of a variable in a
register of the CPU rather than in memory, where normal variables are stored. This meant that
operations on a register variable could occur much faster than on a normal variable because the
register variable was actually held in the CPU and did not require a memory access to determine or
modify its value.