I pretty much understand how the system call works and the need of system calls in general. However, I don't understand why do some system calls like create() file, read() file and close() should be executed only in kernel mode.
For example in create () and read() file, why can't it happen in userspace or usermode ? How could user possibly damage the system by creating and reading a file ? I have the same doubt in case of close() system call too.