Random 1 (#define a 10 and const int a=10)

It is the high season of the job-writing, a few days ago heard that someone encountered this problem: #define A 10 and the const int a=10 difference, nonsense said, below to explain:

#define directive is to define symbolic constants

Const defines a constant variable (the value of a variable cannot be changed)

Symbolic constants simply replace a string with a symbolic constant, which is replaced at the time of precompilation. There is no type, and in memory there is no memory cell with a long symbolic name;

The variable is of the type, and in memory there is a memory unit named after it, and it is possible to measure his length with sizeof.

The difference above means that the first A is of no type and is a symbolic constant

And the second A is of type int, a variable that cannot be changed by a value

OK, do you understand?

Random 1 (#define a 10 and const int a=10)