The development of computer software for analyzing the solar gain through windows of buildings is presented. The program which is capable of stating the hourly values of solar altitude angles, azimuth angles and extra-terrestrial intensity is written in the BASIC Language. The main feature of the program is that it can be used to determine the hourly values of normal solar intensity and solar energy incident on windows treated with reveals, over-hangs and side-fins. Application of the software in analyzing the solar gain through windows in some experiments yield results which are as consistent as those done manually. The experiments show that in every case, reveals have the effect of reducing the incident solar intensities, and hence incident solar energy on windows. Further analysis shows that over-hangs are much more effective in shading than vertical side-fins. (C) 2003 Elsevier Ltd. All rights reserved.