Copyright Digital Equipment Corp. All rights reserved. The storage class of a variable determines when its storage is allocated, whether its contents are preserved across different blocks or functions, and what link-time scope the variable has. Auto variables are allocated at run time. They are not preserved across functions.
Auto is the default storage class for variables declared within a function.
Extern variables are allocated at compile time. They are preserved across functions. There can be only 65,532 extern variables per program. Extern is the default storage class for variables declared outside a function. Globaldef, globalref, and globalvalue variables are allocated at compile time.