Node:Other storage classes, Previous:Static variables, Up:Storage classes

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Other storage classes

There are three more storage class identifiers in C: auto, register, and typedef.

• auto is the opposite of static. It is redundant, but is included in contemporary versions of C for backwards compatibility. All local variables are auto by default.
• register is another outdated C storage class. Defining a variable as register used to store it in one of the computer's registers, a specific location on its processor chip, thereby making code using that variable run faster. These days, most C compilers (including GCC) are smart enough to optimize the code (make it faster and more compact) without the register keyword.
• typedef allows you to define your own variable types. See More data types, for more information.