Operating Systems

The operating system is the first piece of software you need to worry about if you care about privacy. It's the lowest layer between software and hardware and serves as the foundation of all of your computing. If your OS isn't designed with your privacy and security in mind, using private software, regardless of the precautions you take, is ultimately a futile attempt at privacy analogous to putting a band-aid on a wound that needs stitches. There are many Operating System you can use on a day to day, these include Windows, MacOS, Linux distributions and many BSD based OSes.

Privacy Concerns

The operating system is responsible for:

Managing Processes
Managing Memory
Managing the File System
Managing Input/output
Managing an User Interface

All of these can be exploited to compromise data on the computer regardless of the programs being used