## Execution Mode
Starts in Real Mode

# Real Mode
-   16 bit
-   20 bit segmented memory
	-   Max 1 MB memory
-   Direct access to peripherals
-   No memory protection or multitasking
-   BIOS computers start in this mode

# Protected Mode
-   16 bit & 32 bit
-   Max 16 MB of physical memory
	-   Max 1 GB virtual memory
-   Privilege levels and protected memory

# Long Mode
-   64 bit
-   Largely an extension to 32 bit protected mode

# System Management Mode
-   16 bit
-   System-wide functions
	-   Power management
	-   System control hardware
	-   Proprietary OEM code