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Unformatted text preview: [ Viewing Hints ] [ Exercise Solutions ] [ Volume 2 ] [ Free Newsletter ] [ Seminars ] [ Seminars on CD ROM ] [ Consulting ] Thinking in C++, 2nd ed. Volume 1 2000 by Bruce Eckel [ Previous Chapter ] [ Table of Contents ] [ Index ] [ Next Chapter ] 10: Name Control Creating names is a fundamental activity in programming, and when a project gets large, the number of names can easily be overwhelming. C++ allows you a great deal of control over the creation and visibility of names, where storage for those names is placed, and linkage for names. The static keyword was overloaded in C before people knew what the term overload meant, and C++ has added yet another meaning. The underlying concept with all uses of static seems to be something that holds its position (like static electricity), whether that means a physical location in memory or visibility within a file. In this chapter, youll learn how static controls storage and visibility, and an improved way to control access to names via C++s namespace feature. Youll also find out how to use functions that were written and compiled in C. Static elements from C In both C and C++ the keyword static has two basic meanings, which unfortunately often step on each others toes: 1. Allocated once at a fixed address; that is, the object is created in a special static data area rather than on the stack each time a function is called. This is the concept of static storage . 2. Local to a particular translation unit (and local to a class scope in C++, as you will see later). Here, static controls the visibility of a name, so that name cannot be seen outside the translation unit or class. This also describes the concept of linkage , which determines what names the linker will see. This section will look at the above meanings of static as they were inherited from C. static variables inside functions When you create a local variable inside a function, the compiler allocates storage for that variable each time the function is called by moving the stack pointer down an appropriate amount. If there is an initializer for the variable, the initialization is performed each time that sequence point is passed. Sometimes, however, you want to retain a value between function calls. You could accomplish this by making a global variable, but then that variable would not be under the sole control of the function. C and C++ allow you to create a static object inside a function; the storage for this object is not on the stack but instead in the programs static data area. This object is initialized only once, is not on the stack but instead in the programs static data area....
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