Final answer:
The main computer or central system unit should usually be turned on last when powering a system to ensure that all peripheral devices are ready to interact with it.
Step-by-step explanation:
The reason behind this order is that the peripherals/devices may rely on the main system unit to function properly. For example, if you have a printer connected to your computer, the printer needs to establish a connection with the computer before it can be used. Therefore, it is important to power on the peripherals/devices first to ensure proper functionality. On the other hand, the main system unit can be turned on last because it does not depend on any other device for its functionality.
Once the peripherals/devices are powered on, you can then turn on the main system unit. When powering on a system, the device you should typically turn on last is the main computer or central system unit. This is because peripheral devices, such as monitors, printers, and external drives, rely on the main computer for data and will not function until the computer is on. Turning on the central unit last helps ensure that once it is on, all peripheral devices are already powered and ready to receive or send data to the central unit.