After the BIOS transfers control to boot sector, the first megabyte of memory looks like this:
| Address | Size | Name |
| 0x0000:0x0000 | 1024 bytes | Interrupt Vector Table |
| 0x0040:0x0000 | 256 bytes | BIOS Data Area |
| 0x0050:0x0000 | ? | Free memory |
| 0x07C0:0x0000 | 512 bytes | Boot sector code |
| 0x07E0:0x0000 | ? | Free memory |
| 0xA000:0x0000 | 64 Kb | Graphics Video Memory |
| 0xB000:0x0000 | 32 Kb | Monochrome Text Video Memory |
| 0xB800:0x0000 | 32 Kb | Color Text Video Memory |
| 0xC000:0x0000 | 256 Kb1 | ROM Code Memory |
| 0xFFFF:0x0000 | 16 bytes | More BIOS data |