An algorithm for the computer simulation of a solid absorption solar refrigerator, COSSOR, is presented. The algorithm is based on a detailed transient mathematical model of the system. It is a sequential modular program which consists of a relatively short main program and about 50 subprograms which are called by name by the main program or other subprograms. The program is coded in QBASIC, is highly flexible, accurate and fast, and has been tested on a wide variety of personal computers. Predictions of the refrigerator performance obtained using COSSOR compare very well with experimental data over a wide range of operating conditions. It is therefore a useful tool for computer aided design, performance prediction and analysis of the refrigerator, and may find applications in other solar thermal systems. Typical predicted results for some stations are given.