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Diffference between #define and const in C?
  • Difficulty Level : Easy
  • Last Updated : 29 Dec, 2020

#define is a preprocessor directive. Things defined by #define are replaced by the preprocessor before compilation begins. 

const variables are actual variables like other normal variables. 

The big advantage of const over #define is type checking. We can also have pointers to const variables, we can pass them around, typecast them, and any other thing that can be done with a normal variable. One disadvantage that one could think of is extra space for variables which is immaterial due to optimizations done by compilers. 

In general, const is a better option if we have a choice. There are situations when #define cannot be replaced by const. For example, #define can take parameters (See this for example). #define can also be used to replace some text in a program with another text. 

This article is contributed by Abhay Rathi. Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above

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