What is the meaning of le9 used to define infinity

#1

1 - what is le9
2 - its header file
3 - if it i equal to INIT_MAX then what is the difference between using either,

#2

@akb.tech17
1e9 is scientific notation for the number one followed by nine zeros - 1,000,000,000, means 10^9.
it does not require any separate header file you can use it under any header file.
INT_MAX requires separate header file like <limits.h> or < climits > it can’t be used simply with < iostream > ,
you can use both INT_MAX or 1e9 it won’t make any difference.