Oracle Database Discussions

How to calculate number of threads running on Windows 2000 terminal for the oracle process?
I have installed Oracle 9i DataBase with 6 patch(9.2.0.6.0) on Windows 2000 Terminal.
But,after database is started up, when i check up the sessions in v$session view.
It is showing like for SYSTEM osuser alone, 10 ORACLE.EXE sessions running on this server machine in active state.
Why it is creating 10 ORACLE.EXE sessions for a single Oracle Server.
This is the output of v$session view.

SQL> select terminal,osuser,status,sid,serial#,program from v$session;

TERMINAL OSUSER STATUS SID SERIAL# PROGRAM
---------------- ------------------------------ -------- ---------- ---------- ---------------------
IMGDBSVR SYSTEM ACTIVE 1 1 ORACLE.EXE
IMGDBSVR SYSTEM ACTIVE 2 1 ORACLE.EXE
IMGDBSVR SYSTEM ACTIVE 3 1 ORACLE.EXE
IMGDBSVR SYSTEM ACTIVE 4 1 ORACLE.EXE
IMGDBSVR SYSTEM ACTIVE 5 1 ORACLE.EXE
IMGDBSVR SYSTEM ACTIVE 6 1 ORACLE.EXE
IMGDBSVR SYSTEM ACTIVE 7 1 ORACLE.EXE
IMGDBSVR SYSTEM ACTIVE 8 1 ORACLE.EXE
IMGDBSVR SYSTEM ACTIVE 9 1 ORACLE.EXE
IMGDBSVR SYSTEM ACTIVE 10 1 ORACLE.EXE
SUGANTHI_DBA suganthi ACTIVE 11 91 sqlplusw.exe

11 rows selected.

SQL>