Sequential Files and Simple Indexes

• Files started out on tape
  only sequential access
  input and output tapes on separate drives

• When disks arrived files were still processed sequentially

• When disk files became large, sequential searching was slow

• Indexes were added which were simply a file with a list of keys and addresses of data in the larger file

• Managing simple indexes was hard

• A simple index file has similar problems to the original files when it becomes large enough.

• Managing changes was hard