Java is a programming language and computing platform first released by Sun Microsystems in 1995. There are lots of applications and websites that will not work unless you have Java installed, and more are created every day.
IIS is able to impersonate the IUSR_<computername> account because the user name and password for this account are known by IIS. Before returning a page to the client, IIS checks NTFS file and directory permissions to see if the IUSR_<computername> account is allowed access to the file.
IRR: The IRR button is used to compute the internal rate of return. This being the rate at which the NPV equals zero. The location of the IRR key is on the second row fourth column of the calculator.