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. Extern is the default storage class for variables declared outside a function. Globaldef, globalref, and globalvalue variables are allocated at compile time. They are preserved across functions.