CompTIA A+ Certification

When working on operating system problems, a differential diagnosis can start with observing where in the operational cycle the problem occurs. The system operational cycle can be broken into three components:

• System startup, which begins at the point at which the operating system starts to load and it ends when the user can start making use of the operating system;
• The operating phase, which is when the operating system is operational and the user can make use of it; and
• System shutdown, which begins when a user issues a shutdown command and ends when the operating system is unloaded from memory.

There is a natural order to working through these phases. If the operating system starts, you can move on to the operating phase. If the operating system fails to start, you have to resolve that issue before going further.