Q1: What are the three main purposes of an operating system? [3] Q2: [2] What is the main difficulty that a programmer must overcome in writing an operating system for a real-time environment? Q3: [2] Keeping in mind the various definitions of operating system, consider whether the operating system should include applications such as Web browsers and mail programs. Argue both, it should, or it should not, and support your answers. Q4: [2] How does the distinction between kernel mode and user mode function as a rudimentary form of protection (security) system