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True object-oriented languages can protect fields of objects from direct manipulation by other objects' methods. A private field is one that cannot be fetched or updated from any function or method declared outside the object; a private method is one that cannot be called from outside the object. Privacy is enforced by the type-checking phase of the compiler. In the symbol table of C, along with each field offset and method offset, is a boolean flag indicating whether the field is private. When compiling the expression c.f() or c.x, it is a simple matter to check that field and reject accesses to private fields from any method outside the object declaration. There are many varieties of privacy and protection. Different languages allow

In general, these varieties of protection can be statically enforced by compiletime type-checking, for class-based languages.

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