On each of the two competition days, the students are typically given three problems which they have to solve in five hours. Each student works on his/her own, with only a computer and no other help allowed, specifically no communication with other contestants, books etc. Usually to solve a task the contestant has to write a computer program (in C, C++ or Pascal) and submit it before the five hour competition time ends. Later on, the program is graded by being run with secret test data, consisting of multiple (typically 10 or 20) test cases. The contestant is awarded points for each test case that his program solves correctly, and within the given time and memory limit. In some cases, the contestant's program has to interact with a secret computer library, which allows problems where the input is not fixed, but depends on the program's actions - for example in game problems. Another new type of problems has known inputs which are publicly available already during the five hours of the contest. For these, the contestants have to submit the according output file instead of a program, and it is up to them whether they obtain the output files by writing a program (possibly exploiting special characteristics of the input), or by hand, or by a combination of these means.
The scores from the two competition days and all problems are summed up separately for each contestant. At the awarding ceremony, contestants are awarded medals depending on their relative total score. The top 50% of the contestants (i.e. two per country, on average) are awarded medals, such that the relative number of gold : silver : bronze : no medal is approximately 1:2:3:6 (thus 1/12 contestants get a gold medal)