Executes only one program at a time.
Addresses only 1MB at a time.
Directly accesses memory and hardware.
Availible to all modern processors.
Only used by DOS and DOS applications.
Subject to crashes.
Access to all memory.
Manages multiple programmes at once.
Lets the system use virtual memory.
Provides 32-bit access to memory, drivers and i/o transfers.
Each program is assigned a space in memory.
Computer is protected from program errors.
Virtual real mode
Allows real mode apps to run in a protected mode.
Creates virtualmachines for each real mode program.
Each vm receives 1MB of memory and access to hardware.
In a program error only the virtual machine is affected.
vm’s are used to run older programs on newer machines.