Which ACPI power state indicates that the system is fully on?

Which ACPI power state indicates that the system is fully on?

• A. S4
• B. S1
• C. D0
• D. S3

Answer: (C)

The power state that indicates the system is fully on is represented by D0. In this state, the operating system has control of the machine, and all components of the system are powered up and operational. This state allows the CPU and other hardware to perform their full function, enabling the system to execute applications and perform tasks without any limitations on performance or capability. In contrast, the other power states such as S1, S3, and S4 indicate various levels of reduced power consumption. For example, S1 is a low-power state where the CPU stops executing instructions but can quickly resume full operation, while S3, also known as sleep mode, puts the system into a deeper sleep where the system state is preserved, but power to non-essential components is reduced. S4 represents hibernation, where the system saves the current session to disk and powers down completely, requiring a longer time to return to full operation compared to S1 or S3. Thus, D0 is the only state where the system is fully operational.

The power state that indicates the system is fully on is represented by D0. In this state, the operating system has control of the machine, and all components of the system are powered up and operational. This state allows the CPU and other hardware to perform their full function, enabling the system to execute applications and perform tasks without any limitations on performance or capability.

In contrast, the other power states such as S1, S3, and S4 indicate various levels of reduced power consumption. For example, S1 is a low-power state where the CPU stops executing instructions but can quickly resume full operation, while S3, also known as sleep mode, puts the system into a deeper sleep where the system state is preserved, but power to non-essential components is reduced. S4 represents hibernation, where the system saves the current session to disk and powers down completely, requiring a longer time to return to full operation compared to S1 or S3. Thus, D0 is the only state where the system is fully operational.