Definitions

1. File scope: The scope outside of all blocks and classes in a file.

2. Translation unit: A .cc file after all .hh files have been included by the preprocessor.

3. Internal linkage: A name local to its translation unit has ``internal linkage,'' and cannot collide with names in other translation units.

4. External linkage: A name with ``external linkage'' can interact with other translation units at link time.

5. Global identifier: A name with external linkage or a name at file scope in a .hh file. (Potentially useable anywhere in the program).

6. Declaration: Introduces a name into a program. Provides a description of the named entity, but does not create it. Does not result in any memory allocation. A declaration may be repeated many times. For example, the following are declarations:
   

    
                       class Point;
                       double f(int i, int j);

7. Definition: Provides a unique description of an entity. May result in memory allocation. There must be exactly one definition of an entity. For example:
   • A function body:

                         float recip(float x) {
                           return 1/x;        }

   • A class body:

                         class Ruler {
                           // private and public variables
                           // and methods declared or defined
                           // here inside the class body   };

   • Instantiating variables or objects:

                         int x;
                         Ruler yardstick;

8. A definition is also a declaration unless:
   It defines a static class data member or
   It defines a member function of a class, and is not inside the body of code that defines that class.

9. A declaration is also a definition unless:
   It declares a function without specifying its body or
   It specifies ``extern'' and has no initializer or function body or
   It declares a static class data member within a class definition or
   It is a class name declaration or
   It is a typedef declaration.

10. Component: A .hh file together with the corresponding .cc files.

11. Package: A collection of components organized as a physically cohesive unit. (eg: the ``muon'' package would have all the code for muon reconstruction.)