While Bachelor and Master courses are starting to be introduced at German universities, the Diplom is still the most common degree in the natural sciences. For example, computer science students are awarded the degree Diplom-Informatiker, or Dipl.-Inf. for short.
A Diplom course in computer science is usually planned by the faculty for a duration of four and a half years, but there is no fixed timetable, and the majority of students take five to six years, depending on the amount of supplementary courses taken. As well as the final exams, which are taken orally, graduation involves writing a Diplomarbeit, or Diploma Thesis, with a planned duration of six months' full-time work.
The Dipl.-Inf. degree qualifies for post-graduate studies, such as doctorate courses, and is often considered to be roughly equivalent to a Master's degree. For a detailed explanation of the German academic system, see this page by Professor Ladkin of Bielefeld university.