This document discusses operating system concepts including: - The functions of an operating system like overseeing computer operation, file storage/retrieval, and program execution/scheduling. - Operating system architectures with layers like the application, shell, kernel and hardware. - The boot process from BIOS startup, POST hardware checks, and handing over to the operating system bootloader. - How the operating system coordinates running processes and switches between them using techniques like scheduling, dispatching, and context switching. - Methods for handling competition among processes using semaphores and avoiding deadlocks. The document also covers basic security concepts involving user accounts and protection rings.

1. OPERATING SYSTEMS
CS160

2. HISTORY OF OPERATING SYSTEMS
Operating Systems

3. FUNCTIONS OF AN OPERATING SYSTEM
 Oversee operation of computer
 Store and retrieve files
 Schedule programs for execution
 Coordinate the execution of programs

4. BATCH PROCESSING

5. INTERACTIVE PROCESSING

6. OPERATING SYSTEM ARCHITECTURE
Operating Systems

7. SOFTWARE CLASSIFICATION

8. OPERATING SYSTEM ARCHITECTURE
Application
Shell
Kernel
Hardware

9. WINDOWS XP SYSTEM ARCHITECTURE

10. WINDOWS XP SYSTEM ARCHITECTURE

11. OPERATING SYSTEM ARCHITECTURE
Application
Shell
Kernel
Hardware

12. THE BOOT PROCESS: BIOS
 Custom settings are read from CMOS
 Complementary Metal-Oxide Semiconductor
 Memory used to store configurable system
settings
 System setup utility
 Power-on self-test (POST) is run to check
system function

13. THE BOOT PROCESS: POST
 POST
 BIOS instructs CPU to read code stored at various
locations and compares it to known values
 BIOS loads low-level drivers and interrupt handlers
for basic hardware
 Checks video card
 Initializes video BIOS
 Tests video card and video memory
 BIOS information (version, date, manufacturer)
is displayed

14. THE BOOT PROCESS: WARM VS COLD BOOT
 BIOS checks memory location 0x0472
 Value of 0x1234 indicates a reboot and rest of
post is skipped
 Any other value indicates a cold boot and the
following steps are performed
 RAM is tested
 Values are written then read from each memory
cell
 BIOS tests for existence of floppy disks, hard
drive, and optical drives

15. THE BOOT PROCESS: HANDOFF
 After POST BIOS hands off control to operating
system
 BIOS instructs CPU to begin executing the
operating system boot loader
 Code found in sector zero of primary HDD
 Operating system replaces many of the device
drivers and interrupt vectors that BIOS loaded

16. THE BOOT PROCESS: PLUG AND PLAY
ENUMERATION
 The operating system adds special device
drivers called enumerators
 ISA bus enumerator
 SCSI bus enumerator
 PCI bus enumerator
 PCIe bus enumerator
 Port enumerator
 Operating system asks each enumerator to
identify which devices it has and what
resources they require

17. THE BOOT PROCESS: RESOURCE ARBITRATION
 Operating system assigns resources to each
enumerated device
 IRQ
 DMA
 Memory addresses
 If no new devices are discovered, stored PnP
information is used
 Operating system loads appropriate high-level
device drivers for each PnP device
 Drivers initialize each device

18. THE BOOT PROCESS: FINISHING UP
 Operating system mounts disk drives for use
 Video drivers are installed to allow for use of
video hardware
 Operating system services are initialized
 User logon screen displayed

19. COORDINATING THE MACHINE’S
ACTIVITIES
Operating Systems

20. PROCESSES
 Program: a set of instructions given to a
computer
 Process: a program in execution
 Process state: the current status of a process
including the contents of the relevant CPU
registers

21. PROCESS STATE DIAGRAM
New
Ready
Admitted
Running
Scheduler dispatch
TerminatedExit
Interrupt
Waiting
I/O or event waitI/O or event completion

22. PROCESS ADMINISTRATION
 Processes compete for operating system
attention and computer resources
 Operating system coordinates execution of
processes
 Scheduler
 Dispatcher

23. SCHEDULER
 Scheduler manages a
pool of processes
which are currently
being executed
 Adds new processes
 Removes completed
processes
 This pool is a
collection of process
control blocks (PCBs)

24. DISPATCHER
 Responsible to ensuring processes get
scheduled for CPU time
 The act of changing from one process to
another is called a context switch
 PCBs are packed/unpacked
 Cooperative multitasking
 Processes remove themselves from running state
 Preemptive multitasking
 Dispatcher evicts process when time slice expires
 Occurs on interrupt

25. CONTEXT SWITCHING

26. HANDLING COMPETITION AMONG
PROCESSES
Operating Systems

27. SEMAPHORES

28. DEADLOCK

29. SECURITY
Operating Systems

30. USER ACCOUNTS
 Privileges assigned according to account type
 Super User or Administrator
 Standard user
 Other role-based accounts

31. HIERARCHICAL PROTECTION DOMAINS
(PROTECTION RINGS)
Least Privileged
Most Privileged
Application
Shell
Ring 3
Ring 2
Kernel
Ring 1
Hardware
Ring 0