Operating System Boot Process
This is just a basic description of how a Pentium computer boots.
- First the BIOS is loaded from motherboard RAM.
- BIOS checks how much RAM is installed.
- Other devices like keyboard / mouse are checked.
- Then checks ISA and PCI busses.
- BIOS then determines the boot device listed in CMOS memory.
- Usually floppy -> CD -> HDD
- The first sector of boot device is read and loaded
- Examines the partition table at end of the boot sector, to determine which partition to use.
- The boot loader is read from that partition.
- Boot loader loads the OS
Major OS Types
Heavily oriented towards processing many jobs at once. However nowdays it is being slowly replaced by UNIX.
They run on servers, usually very large PCs or even mainframes. They serve multiple users at once.
Common server OSes: Solaris, FreeBSD, Linux and Windows Server.
Nowdays most OSes are multiprocessor, for example Windows and Linux. Since most PCs have multiple cores, or even multiple CPUs.
Personal Computer OS
This is widely known, for example macOS, Windows and Linux. They usually support multiprogramming, and aims to provide the best experience for a single user.
Old school Symbian OS and Palm OS, nowdays it is Android, which is Linux, and iOS, which is UNIX.
Major difference between embedded OS and others is: It does not need to run untrusted software. That leads to simplifications. For example, a MP3 player.
Sensor Node OS
TinyOS is one of the wellknown ones. These OS are found on sensors, which usually wirelessly communicate with eachother and protect building parameters.
These are used in assembly lines. Time is critical, for hard real-time systems, deadlines must be met. Soft real-time systems can miss some deadlines.
Because time is critical, usually there is no protection.
Smart Card OS
The smallest you can get is smart card OSes. Sometimes smart card OSes runs JVM (Java). They are usually powered by the machine they are in contact with.
What is an OS
----------------- Applications ----------------- Operating System ----------------- Hardware
- Provides services
- Resource manager
- Control program (protection)
A process contains
- An address space
- Set of OS resources
- Set of general-purpose registers with current values