The 13th International Olympiad in Informatics was held in Tampere, Finland in 2001. There were two competition days, with 3 tasks given to the competitors on each day. You can see the tasks, test cases and solutions below.

Day 1:
      Mobile Phones
      Ioiwari Game
      Twofive

Day 2:
      Score
      Double Crypt
      Depot

Other materials:
      Test cases and some source codes
      Solutions and handouts


Note that the grading model changed at IOI'94 and beyond.
Before IOI 1994, a human evaluator would sit behind the competitor's computer and do the testing manually (enter test data through the keyboard, check the output on the screen). Starting from IOI 1994, an automatic grading process is used, with test input defined in files.