on dos bootstrap io.sys mean

[barb]

 I AM IN A CLASS THAT IS TEACHING ME HOW TO REPAIR PC AND TAKE MY A+ CERT. BUT I AM NOT UNDERSTANDING WHAT I/O.SYS MEANS AND AUTO.EXE.BAT I AM TAKING MY TEST ON MON. AND I KNOW OUR TEACHER WILL ASK THIS . SO CAN ANY ONHELP, ALSO IF YOU NO THE WINDOW BOOTSTRAP I AM NOT SURE WHAT THIS MEANS TO USER32.DLL , AND NETWORK.INI AND PROROCOL.INI PROGRA.INI I LOOKED ON THE COMPUTERHOPE.COM BUT IT WILL NOT TELL ME WHAT IT MEANS SO IF ANY ONE CAN HELP.  :-/