Difference between Declaration and Definition of a Variable in C

Question: What is the difference between declaration and definition of a variable?

Answer: Declaration specifies the properties of a variable. For example:

    int x;              /* x is an integer */
    int roll_no[];      /* roll_no is an array of integers */

Definition declares a variable and causes the storage to be allocated. For example:

    int x = 10;         /* x is declared as an integer and allocated space and initialized to 10 */
    int roll_no[100];   /* roll_no is declared as an array of integers, allocated space for 100 integers */

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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