Storage classes and types

Associating identifiers with objects requires each identifier to have at least two attributes: storage class and type (sometimes referred to as data type). The C++Builder compiler deduces these attributes from implicit or explicit declarations in the source code.

Storage class dictates the location (data segment, register, heap, or stack) of the object and its duration or lifetime (the entire running time of the program, or during execution of some blocks of code). Storage class can be established by the syntax of the declaration, by its placement in the source code, or by both of these factors.

The type determines how much memory is allocated to an object and how the program will interpret the bit patterns found in the object's storage allocation. A given data type can be viewed as the set of values (often implementation-dependent) that identifiers of that type can assume, together with the set of operations allowed on those values.
The compile-time operator, sizeof, lets you determine the size in bytes of any standard or user-defined type.

Scope
The scope of an identifier is that part of the program in which the identifier can be used to access its object. There are six categories of scope: block (or local), function, function prototype, file, class (C++ only), and namespace (C++ only). These depend on how and where identifiers are declared.

Function.
The only identifiers having function scope are statement labels. Label names can be used with goto statements anywhere in the function in which the label is declared. Labels are declared implicitly by writing label_name: followed by a statement. Label names must be unique within a function.

Block.
The scope of an identifier with block (or local) scope starts at the declaration point and ends at the end of the block containing the declaration (such a block is known as the enclosing block). Parameter declarations with a function definition also have block scope, limited to the scope of the block that defines the function.

Function prototype.
Identifiers declared within the list of parameter declarations in a function prototype (not part of a function definition) have function prototype scope. This scope ends at the end of the function prototype.

File.
File scope identifiers, also known as globals, are declared outside of all blocks and classes; their scope is from the point of declaration to the end of the source file.

Class (C++). A class is a named collection of members, including data structures and functions that act on them. Class scope applies to the names of the members of a particular class.Classes and their objects have many special access and scoping rules;
Condition (C++). Declarations in conditions are supported. Variables can be declared within the expression of if, while, and switch statements. The scope of the variable is that of the statement. In the case of an if statement, the variable is also in scope for the else block.

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