Status: ✅ COMPLETE
Scope: The first program a PC runs: what the BIOS and UEFI are, how they check and start the hardware (POST), how they find and trust the operating system (boot manager, ESP, Secure Boot), where settings are stored, and the settings you will meet in the setup screen
Time to complete: 90–120 minutes of reading + lab
Prerequisites: Chapter 1 (Complete Computer Architecture), Chapter 2 (CPU Internals), Chapter 3 (RAM and Memory Internals), Chapter 4 (Motherboard and Hardware Communication, especially Section 8: Firmware and ROM)
What you'll know after: What happens between pressing the power button and Windows starting, the difference between BIOS and UEFI, what MBR, GPT and the EFI System Partition are, why Secure Boot exists, and how to open and safely use the firmware setup screen
INTRODUCTION
Chapter 4 ended with a chip on the motherboard that holds the very first program. This chapter opens that chip. Before Windows, before drivers, before the desktop, the firmware has to wake up the hardware, make sure it works, and find the operating system. For decades that firmware was the BIOS. Today it is UEFI.
This chapter uses real images: a classic BIOS setup screen and a diagram of the modern disk layout (GPT). It uses plain words, and every technical term is explained the first time it appears. You will also use Windows tools such as msinfo32, PowerShell and bcdedit to look at your own PC.
This chapter explains:
- What the BIOS is, where it came from, and why its 16-bit design became a limit
- How the BIOS is built: boot ROM, real mode, interrupts, services and option ROMs
- What POST does, step by step, and what beep codes mean
- What UEFI is, and how it beats the BIOS (GPT, 64-bit, Secure Boot, mouse screens)
- How UEFI is built inside: firmware volumes, applications, protocols, the ESP and the boot manager
- How Secure Boot uses keys and signatures to stop bootkits
- Where settings live: CMOS, NVRAM and the coin battery
- The settings you will meet: boot order, AHCI/RAID, XMP, virtualization, TPM and fans
CHAPTER OUTLINE
- Section 1: What is BIOS?
- Section 2: BIOS Architecture
- Section 3: POST (Power-On Self Test)
- Section 4: What is UEFI?
- Section 5: UEFI Internals
- Section 6: Secure Boot
- Section 7: CMOS and Settings Storage
- Section 8: BIOS/UEFI Settings
- Practical Lab: Entering BIOS/UEFI
- Knowledge Check
Chapter Status: Complete
Estimated reading time: 100 minutes
Practical time: 30 minutes
Knowledge check time: 30 minutes