This is a typical Memory Map of a PC.

 Hex Address      Purpose

     0-3FF          Interrupt Vectors
   400-47F          ROM-BIOS RAM
   480-5FF          Basic and system function RAM
   600-9FFFF        Program Memory
0A0000-0AFFFF       VGA/EGA Video Memory
0B0000-0B0FFF       Monochrome Video Memory
0B8000-0BFFFF       CGA Video Memory
0C0000-0CFFFF       Hard Disk ROM
0D0000-0D7FFF       Spare ROM
0D8000-0DFFFF       Spare ROM
0E0000-0E7FFF       Spare ROM
0E8000-0EFFFF       Spare ROM
0F0000-0F3FFF       Spare ROM
0F4000-0F7FFF       Spare ROM
0F8000-0FDFFF       Spare ROM
0FC000-0FDFFF       ROM-BIOS
0FE000-0FFFFF       ROM-BIOS

This memory map assumes Real Mode operation.