CER (Serbian: æøÃÂðÃÂÃÂúø ÃÂûõúÃÂÃÂþýÃÂúø àðÃÂÃÂýðà/ Cifarski Elektronski RaÃÂunar - Digital Electronic Computer) model 20 was an early digital computer developed by Mihajlo Pupin Institute (Serbia). It was designed as a functioning prototype of an "electronic bookkeeping machine". The first prototype was planned for 1964.