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Difference Between Declaring a Variable and Defining a Variable

By Dinesh Thakur

Declaration of a variable in C hints the compiler about the type and size of the variable in compile time. Similarly, declaration of a function hints about type and size of function parameters. No space is reserved in memory for any variable in case of declaration.

Example: int a;
Here variable ‘a’ is declared of data type ‘int’

Defining a variable means declaring it and also allocating space to hold it.

We can say “Definition = Declaration + Space reservation”.
Example: int a = 10;

Here variable “a” is described as an int to the compiler and memory is allocated to hold value 10.

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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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