OS Introduction
Computer
Software
User Mode
User interface program
Features
- A subset instructions are available
- The instructions that affect control of hardware or IO is forbidden in this mode
Kernel Mode
OS runs in here， provides the base for all the other software
Features
- Complete Access to Hardware
- execute any instructions the machine is capable of executing
Hardware
What is An OS?
A software runs in kernel mode
which can provide a clean abstract set of resources instead of the messy hardware
OS as an extended machine
- no one want to deal with disk at hardware level
- OS contains many drivers for controlling IO devices
- The abstraction is the key to manage all these complexities
OS as a Resource manager
time
- e.g. multiple print jobs
space
History
tl;dr
Computer Hardware Review
Processors
- CPU is Brain
Memory
Disks
IO devices
