FAT12

Preface

1. Why FAT12?
2. Who This Book Is For
3. What You Will Build
4. What You Will Learn
5. A Note on Style
6. How to Read This Book
7. About the Author
8. Feedback

Prerequisites

1. Operating System
2. C Compiler and Dependencies
3. Editor and Hex Editor
4. Getting the Code (Optional)

Part I: Reading

Chapter 1: Hello, Disk!

1. What Is FAT12?
2. Creating a Virtual Disk
3. Sectors and LBA
4. A Tale of Four Regions
5. Project Layout
6. A Portable Foundation: The BlockDevice
7. Reading Sector 0
8. Tracing the Translation
9. Production Notes
10. What Is Next

Chapter 2: The Blueprint (BPB)

1. Boot Sector Structure
2. Mapping Bytes to Structs
3. The FAT12 Library
4. The Info Command
5. Debugging
6. Production Notes
7. What Is Next

Chapter 3: The Root Directory

1. What Is the Root Directory?
2. Decoding Timestamps
3. Where Is the Root Directory?
4. Geometry Functions
5. Loading the Root Directory
6. Formatting an 8.3 Name
7. The ls Command
8. Updating the Header
9. Building
10. Verification: Create Real Files
11. Debugging with a Hexdump
12. Production Notes
13. What Is Next

Chapter 4: Reading Files

1. What the FAT Actually Is
2. Where the FAT Lives
3. Data Region Geometry
4. Reading an Entry
5. Loading the FAT
6. Reading a Cluster Chain
7. File API
8. The cat Command
9. Updating the Header
10. Building
11. Verification: Create a Real File
12. Hexdump Verification
13. Multi-Cluster File
14. Production Notes
15. FAT Family: FAT16 and FAT32
16. What Is Next

Part II: Writing

Chapter 5: Full Path Walking

1. Subdirectories in FAT12
2. Reading a Subdirectory from a Cluster Chain
3. Splitting a Path into Tokens
4. Finding an Entry by Name
5. The Centerpiece: fat12_resolve_path
6. Wiring into fat12_opendir
7. Wiring into fat12_open
8. Updating the CLI Commands
9. Building
10. Verification: Nested Directories
11. Production Notes
12. The FAT Family: FAT32 Root Cluster
13. What Is Next

Chapter 6: Writing Files

1. The Write Path
2. Writing FAT Entries
3. Finding Free Clusters
4. Allocating a Chain
5. Writing Data Clusters
6. Syncing the FAT
7. Loading the Parent Directory
8. Finding a Free Slot
9. Formatting 8.3 Names
10. Creating a Directory Entry
11. Updating the File Struct
12. Extending fat12_open
13. Adding fat12_write
14. Updating fat12_close
15. Updating the Header
16. Updating the cat Command
17. The Write CLI Command
18. Building
19. Verification
20. Production Notes
21. FAT Family: Writing Across FAT Variants
22. What Is Next

Chapter 7: Creating Directories

1. What We Need to Write
2. Splitting a Path into Parent and Name
3. The fat12_mkdir Function
4. Updating the Header
5. The mkdir CLI Command
6. Building
7. Verification
8. Production Notes
9. FAT Family: Directories Across FAT Variants
10. What Is Next

Chapter 8: Deleting Files and Directories

1. The Deleted Entry Marker
2. Freeing a Cluster Chain
3. The fat12_remove Function
4. The fat12_rmdir Function
5. Updating the Header
6. The rm and rmdir CLI Commands
7. Building
8. Verification
9. Production Notes
10. FAT Family: Deleting Across FAT Variants
11. What Is Next

Chapter 9: Renaming and Moving

1. The Two Cases
2. The Remaining Helper
3. The fat12_rename Function
4. Updating the Header
5. The mv CLI Command
6. Building
7. Verification
8. Production Notes
9. FAT Family: Rename and Move Across FAT Variants
10. What Is Next

Part III: Advanced

Chapter 10: Formatting a Disk

1. What We Are Building
2. Computing the Layout
3. Updating the Header
4. The format CLI Command
5. Building
6. Verification
7. Production Notes
8. FAT Family: Formatting Across FAT Variants
9. What Is Next

Chapter 11: Into the Kernel

1. What Changes, What Does Not
2. The Freestanding Environment
3. ATA PIO Block Device
4. The Kernel Entry Point
5. Linking at 1 MB
6. kernel_main
7. Building
8. Running in QEMU
9. Debugging Tips
10. Production Notes
11. FAT Family: Multiplatform Payoff
12. What Is Next

Conclusion

1. The Architecture
2. What Is Next
3. Thank You