how to set password while loging into database

Hi,

Actually i installed postgresql 8.0 on my windows system. After that i want
to connect database through command prompt so i type like this
c:\programfiles\postgresql\8.0\bin>psql -U postgres -d mydb
when i typed the above command then it asking password, when i give password
it is able connect otherwise it won't
Here what my problem is in psql command i want to give password after user
name, it should not ask me onceagain password, so is there any option to
give password within psql command. You can ask me why i am asking like this
if i want to run a batch file then i can not enter for each every command
the password, so pls help me and tell me how to set password to commands
like psql and createdb and other commands. Pls help it's very urgent for me.

My email id is jith_n(at)yahoo(dot)com

Thanks,
J R