FAT16

This repo contains a few things to help you find / calculate FAT16 properties, ...

Disclaimer

The info in this repo may contain errors. Please do not rely on this and always check it for yourself!

Table of contents

• GPT Header
• GPT Entry
• Boot Sector
• • Disk Layout
• Files & Directories
• • Time
• • Date
• Sources

GPT Header

GPT Partition Entry

Boot Sector

Disk Layout

• Boot Sector Address [HEX] = First LBA (GPT Entry, DEC) * 512
• Size of cluster [BYTES] = Bytes per sector * Sectors per cluster
• First FAT Address [HEX] = Boot Sector Address + Size of cluster [IN DEC]
• Root Directory Address = First FAT Address + (Small number of sectors * Sectors per cluster) [HEX]
• Root Directory Size [BYTES] = Number of possible root entries * Directory Entry size (often 32 bytes)
• Data Region Address = Root Directory Address + Root Directory Size [IN HEX]
• Total FAT16 Volume in Bytes = Small number of sectors * Bytes per sector

Files

• To find the next cluster index = First FAT Address + Previous Cluster * 2
• File contents of the cluster = Start of data region + cluster_size * (cluster_index - 2)

Time

1. First 5 bits for hours
2. Next 6 bits for minutes
3. Last 5 bits for seconds (you have seconds multiply by 2 to get the value, eg.: 00011 => 3, 3 * 2 => 6 seconds)

Date

1. First 7 bytes years since 1980 (eg.: if value in dec is 28, 1980 + 28 = 2008)
2. Next 4 bits for the month
3. Last 5 bits for the day

Sources

• UCLL
• Pieter Philippaerts