Basic question about Apache+Tomcat Memory usage

[srini]

hi users,
        i have  this basic question in mind from so many days but din't get
an answer for it.
         when i try to execute a simple JSP or Servlet , generally first
time my CPU usage goes to 80-100%.I tried with default examples which comes
with Tomcat. where as i have seen big application which don't use that much
memory even u do some heavy jobs.
 Why is it so ???

 System configuration:
        Pentium3    900mHz processor   256MB Ram.
        Operating system:  win2K
        Tomcat 3.2.2

Thanks in advance.

-srini