This memorandum contains the detailed solution to four classroom problems of Elementary Computer Science. They are adequate for second semester students. The first problem is a simple stocks control application. It involves the use of sequential text files. And the design calls also for the use of several data structures: Tables and lists. The second problem is a very simplified version of printed circuit design. It involves some geometric calculations: straight segment intersections. The third problem is a pattern recognition problem. It deals with the detection of given patterns inside a bitmap table, which presumably has been obtained through digitization of a picture. The fourth problem is a path planning problem. It takes some of the ideas of the travelling salesman problem, but the specification is much more relaxed and, therefore, the problem and its resolution are easier and shorter. The last three problems are strongly related to Computer Graphics.