What is#define

Question

hi

Answer 1

Whatever you define with #define will be replaced with its definition once the code compiles.
Example:
#define MAX 64
Now every time MAX appears in your code it will be replaced by the value 64.
int a[MAX]; /* this turns into 'int a[64];'
This is quite useful for C where you can't create arrays with variable length. However you can still use this in C++ if you want to*/

A even better use of define (and a more complex one) is macros.
Let's start with a simple macro that will return the absolute value (turns the value positive) for a given variable:
#define abs(a) ((a) < 0 ? -(a) : (a))
Usage:
y = abs(x); /* this will set y to the absolute value of x */
Once again the compiler replaces abs(x) with ((x) < 0 ? -(x) : (x)) even before running the code. This is the big difference between macros and functions.

You can use #define with anything you want, even names of other functions or variables. The precompiler will replace everything with the defined name with its definition.

Answer 2

#define lets you define the language on your own, for example,

#define print cout

print << "Hello World!";
//This will work as you have defined cout with print.

Answer 3

plz tell in other way