What is cold boot (hard boot)?

A cold boot, also known as a hard boot, is the process of starting a computer from a state of being completely unpowered. When the power button is pressed, the system initiates a full startup sequence, beginning with the Power-On Self-Test (POST) conducted by the firmware (BIOS/UEFI). This test verifies that core hardware components are functional before the operating system is loaded from storage into memory. This is the standard method for turning on a computer that has been shut down.

B. This describes a warm boot (or soft boot), where the computer restarts without being fully powered down, often initiated via the operating system.
C. This describes the shutdown process, which powers the computer off, and is the opposite of booting.
D. This describes waking a computer from a low-power sleep or hibernate state, which restores the previous session rather than performing a full startup.

1. Patterson, D. A., & Hennessy, J. L. (2017). Computer Organization and Design: The Hardware/Software Interface (5th ed.). Morgan Kaufmann. In Chapter 5, the boot sequence is described as initiating from a power-on state, which is the definition of a cold boot. The text distinguishes this from a system reset (warm boot).

2. Stallings, W. (2018). Operating Systems: Internals and Design Principles (9th ed.). Pearson. In Chapter 2, Section 2.2 "Basic Elements," the boot process is detailed as starting from a powered-off state, where the processor executes firmware code to initialize the system and load the OS, which is the essence of a cold boot.

3. Tanenbaum, A. S., & Bos, H. (2015). Modern Operating Systems (4th ed.). Pearson Education. Chapter 1, Section 1.6.1 "The BIOS" describes the boot process starting when the computer is turned on (a cold boot), initiating the POST and loading the operating system loader.