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Home » C » Variables » What is a Storage class
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What is a Storage class

By Dinesh Thakur

A storage class specifies how the variables are used in the program.

We’ll be covering the following topics in this tutorial:

  • Static storage class or variable
  • Register storage class
  • Automatic storage class or variables
  • External Storage class or Global variable

Static storage class or variable

A variable is declared to be static by prefixing its normal declaration with the keyword static, as in static int a;

Since the property of a variable may be stated in any order we could also use int static a; Static variables can be declared within a function. These variables retain their values from the previous call. i.e., the value that they had before returning from the function.

Register storage class

Register variables are stored in the register of the microprocessor. The number of variable which can be declared register are limited. This means that the variable has a maximum size equal to the register size. If more variables are declared as register variable, they are treated as auto variables. A program that uses register variables executes faster as compared to similar program without register variable.

Automatic storage class or variables

The scope of an automatic variable is only for the block, or any block within the block, in which it appears. All variables declared within a function are auto by default. A variable can be defined as automatic by placing the keyword auto at the beginning of the variable declaration.

Example: auto int a;

External Storage class or Global variable

External variables are global to the file in which they are defined. External variables are used only when all functions needed a particular variable. It retains the assigned value within the scope. In the following program variable i is an external variable.

Example: extern int a;

You’ll also like:

  1. C storage class Specifiers
  2. Storage of Signed Integers
  3. What is scope & storage allocation of extern and global variables
  4. What is scope & storage allocation of register, static and local variables
  5. Primary Storage – What is Primary storage?
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About Dinesh Thakur
Dinesh ThakurDinesh Thakur holds an B.C.A, MCDBA, MCSD certifications. Dinesh authors the hugely popular Computer Notes blog. Where he writes how-to guides around Computer fundamental , computer software, Computer programming, and web apps.

Dinesh Thakur is a Freelance Writer who helps different clients from all over the globe. Dinesh has written over 500+ blogs, 30+ eBooks, and 10000+ Posts for all types of clients.


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