In C, #define is a preprocessor directive that is used to define a constant value for a symbol. It does not create a variable and does not use memory at runtime. It is replaced by its value at the preprocessing stage before the compilation starts. It does not have a memory location. Instead, the preprocessor replaces all instances of the symbol in the code with its defined value before the code is compiled. Therefore, it cannot be type-checked and cannot be passed as an argument to a function.
const is a keyword that is used to declare a variable as a constant and they are handled by the compiler. It creates a variable that cannot be modified after it is initialized. This variable has a memory location and uses memory at runtime. They can be type-checked and can be passed as an argument to a function. The type checking can help to detect errors and potential bugs in the code during the compilation stage.
In short, #define is used to define a constant value for a symbol, and const is used to declare a variable that cannot be modified after it is initialized and provides type checking.
Since const variables are considered variables, they have a memory location and can be assigned a pointer. This means that you can use pointer operations such as typecasting, moving addresses, and passing them as arguments to a function. However, you cannot change the value of a const variable through a pointer.
#define cannot be replaced by const in all situations. #define can take parameters and can be used to replace text in a program with another text, which is not possible with const. #define is useful for simple macro substitution and can be used to define constants that do not require type checking.
In general, it is recommended to use const instead of #define whenever possible, because const provides type checking and pointer operations, but it is important to consider the specific use case and decide which one is more suitable for the given scenario.
