the pound sign（#）targets the complier pre-processor?what is the meaning of this sentence

Question

1.# is aim at the pre-processor ?
2.pre-proccessor is what?

Answer 1

Preprocessor directives are lines included in the code of programs preceded by a hash sign (#). These lines are not program statements but directives for the preprocessor.

Answer 2

In computer science, a preprocessor is a program that processes its input data to produce output that is used as input to another program.

A preprocessor is a "machine" that hides boring and simple code from us, thus making the important parts of the code more readable.

Answer 3

In C and C++, the preprocessor allows you, among other things, to do the following:
-Allows defining constants and functions with #define, which will be substituted before the source gets to the compiler
-Yo can choose which code gets to de compiled with #if #ifndef etc. This allows prevent functions from being defined twice. For example, you include a file the code online gets to the compiler (#ifndef //if not defined) if a certain constant has not been defined (such as the name of the file). Otherwise the code gets to the compiler and the constant you chose is defined (no value needed).

Moreover, macro function parameters can be substituted in special ways (such as pasting the parameter as text on the part you want) since this is not at runtime, which may improve readability. However, they have some flaws I definitely recommend you to search