cs160 chapter 3
TRANSCRIPT
OPERATING SYSTEMS
CS160
HISTORY OF OPERATING SYSTEMS
Operating Systems
FUNCTIONS OF AN OPERATING SYSTEM
Oversee operation of computer
Store and retrieve files
Schedule programs for execution
Coordinate the execution of programs
BATCH PROCESSING
INTERACTIVE PROCESSING
OPERATING SYSTEM ARCHITECTURE
Operating Systems
SOFTWARE CLASSIFICATION
OPERATING SYSTEM ARCHITECTURE
Application
Shell
Kernel
Hardware
WINDOWS XP SYSTEM ARCHITECTURE
WINDOWS XP SYSTEM ARCHITECTURE
OPERATING SYSTEM ARCHITECTURE
Application
Shell
Kernel
Hardware
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
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
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
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
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
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
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
COORDINATING THE MACHINE’SACTIVITIES
Operating Systems
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
PROCESS STATE DIAGRAM
New
Ready
Admitted
Running
Scheduler dispatch
TerminatedExit
Interrupt
Waiting
I/O or event waitI/O or event completion
PROCESS ADMINISTRATION
Processes compete for operating system attention and computer resources
Operating system coordinates execution of processes
Scheduler
Dispatcher
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)
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
CONTEXT SWITCHING
HANDLING COMPETITION AMONG
PROCESSES
Operating Systems
SEMAPHORES
DEADLOCK
SECURITY
Operating Systems
USER ACCOUNTS
Privileges assigned according to account type
Super User or Administrator
Standard user
Other role-based accounts
HIERARCHICAL PROTECTION DOMAINS
(PROTECTION RINGS)
Least Privileged
Most Privileged
Application
Shell
Ring 3
Ring 2
Kernel
Ring 1
Hardware
Ring 0