What is data storage in c plus plus?

Answer 1

A storage class is not a class as such, it is a modifier. C++ provides several built-in storage classes: auto, register, static, extern and mutable.

The auto storage class is implied for all function local variables and it can only be used in functions. Since it is implied it is rarely used. However, with C++11, the auto keyword has an alternative use, allowing unambiguous types to be deduced without the need to explicitly declare their type. This greatly simplifies code where the type is of little importance to the reader, and is particularly useful when iterating through an STL container as it greatly simplifies and shortens the declaration of the for statement that controls the loop.

The register storage class can be used for any variable that will fit in a CPU register. Since register variables do not exist in RAM, they have no address. Declaring a register variable is not a guarantee that the variable will be stored in a register, only that it might be. Simple variables such as counters are good candidates for register variables, however your compiler should be able to automatically determine when to use a register rather than RAM for a variable.

The static storage class ensures that a variable remains in memory at all times. This does not mean the variable is accessible at all times, however, since visibility is ultimately determined by the variable's scope. However, when you modify a static variable that is in scope, it will maintain that value even when it falls from scope (static variables are never destroyed). All static variables must be initialised with a value and each time the program is run, they will default to the initial value.

Class member functions as well as variables can be declared static. Static members of a class are local to the class, rather than to an instance of the class. They are generally used to provide internal class functionality or information that is common to all instances of the class (much like global functions and variables, but scoped to the class). Public static members are also accessible outside of the class, even when no instances of the class exist.

Extern provides external linkage to a global variable that is defined in another file. This is typically used when two or more source files share the same global variable. One file defines the global while all others declare it external.

The mutable storage class is only used in classes, and allows the member to override the constness of the class. That is, when calling constant member functions, the class' mutable members can be modified while the immutable (normal) members remain constant. Mutable members are typically used internally be the class, such that the external "state" of the class can remain constant.

Answer 2

Integer: int [This can store Negatives and Positives but no decimals]

Floating point:

double [This can store negatives and positives and decimals]

float [This is rarely used]

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Answer 3

Data storage has two meanings: data that is stored in working memory (RAM) and data that is stored in mass storage media (disk files, flash-drives, laser disc, tape, etc).

In C++ and most other languages, data storage usually refers to working memory where data is stored in variables and constants. The type of the variable or constant determines the type of the datum stored in the memory allocated to the variable or constant.