Random access files?

[jframe]

i was reading how to use random access files, but it says each field should be of the same length inorder for the seek() to be used. but we cannot keep the fields of fixed length, say names and addresses will be of different length for different records....and i wanted to use the random, but this is confusing?

also what i want is
like i have three fields, first is a serial number, second name and third is say address, how do i make this fixed lenght?
also when i will view this..i want to view them by serial number like when user puts 2 the record number 2 should show, like all the three fields of record 2. please help....