Disk Sectors Critical to the Startup Process

There are two sectors on the disk that are critical to starting the computer:

• Master Boot Record.
• Partition Boot Sector.

These sectors contain both executable code and the data required by the code. For more information about the startup process, see "What Happens When You Start Your Computer," presented later in this chapter. For a description of problems that you might encounter with these two sectors, see Chapter 6, "Troubleshooting Startup and Disk Problems."

Note

Numbers larger than one byte are stored on x86-based computers in little endian format. For example, the sample value for the Relative Sector field in Table 3.1, 0x3F000000, is a little endian representation of 0x0000003F. The decimal equivalent of this little endian number is 63. Because most problems with the Master Boot Record and Partition Boot Sector occur on x86-based computers, the examples of these disk sectors are hexidecimal dumps from x86-based computers.