The term “closed source” usually refers to computer programs whose source code is not accessible to the general public. This model is also known as CSS in short. The source code is protected under closed source software. The piece of software can only be modified by the single person or entity who developed it. Closed source software is expensive, and in order to use it, a user must possess a legitimate license. It also placed several constraints on users’ ability to use and modify software since it gives an authenticated license.
Skype, Java, Adobe products, Virtual Box, Google Earth, Microsoft Office, VMwareServer, Opera, and others are some examples of closed-source software.