What is the difference between #include<stdio.h> and #include"stdio.h" ??

Answer 1

#include <stdio.h> only checks the default C++ directories for that file.
#include "stdio.h" also checks the program file's directory and (depending on the compiler and it's settings) other custom ones.

Answer 2

<header>
it first check library files in std include folder then program folder.
"header"
in this vice versa
first in program folder then std lib folder.