Stream is an array that store the input of user
the size of stream is 256 byte
the array type is char
all the stream stop reading when meet space
include in <iostream>
cin is the stream take input from keyboard
and it is default stream name
include in ''
streamstring is a type that reading from string
like cin, it can load string 123 to int 123
include in <fstream>
fstream is a type that reading from file
.eof() return true if the input is end (in cin eof is Ctrl + d) and it set fail() to 1
.fail() return true if bad input (such as a to int)
.clear() reset the fail() flag
.ingore(1000, '\n') ignore 1000 char or the \n <---------important for cleaning error
.open("./file.txt") open the ./file.txt
.is_open() return true if the file open
.close() close the file