A very short overview is given of the principles of databases. The entity relationship model is used to define the conceptual base. Furthermore file management, the hierarchical model, the network model, the relational model and the object oriented model are discussed During the second world war, computers were used for encoding and decoding messages of the English and German army. Only after the war the computers were used for more reasonable and economical reasons. In the beginning of the fifties problems with typically a small amount of input data but for which complex calculations have to be made, were solved using computers. This was due to the small amount of memory and the long access time that was needed. Typical programming languag...