operating systems
DESCRIPTION
Operating Systems. Summer 02 CPS 1 Shannon Pollard. Computer Services. What things can your computer do? Calculator Word processing Web browsing Photoshop Paint program Games. These are all pieces of Software!. Software. Software applications usually have very nice interfaces – - PowerPoint PPT PresentationTRANSCRIPT
Operating Systems
Summer 02
CPS 1
Shannon Pollard
Computer Services
What things can your computer do?
• Calculator
• Word processing
• Web browsing
• Photoshop
• Paint program
• Games
These are all pieces of Software!
Software
Software applications usually have very nice interfaces –
• Buttons
• Icons
• Menus
• Instructions
• Graphics
Computer Components
How does the computer perform these functions?
• Memory
• Disk drive
• Circuit Board
• Keyboard
• Monitor
These are pieces ofHardware!
Hardware
Hardware components usually have pretty difficult interfaces. Machine Language Program for MIPS Machine
[0x00400000] 0x8fa40000 lw $4, 0($29) ; lw $a0, 0($sp) [0x00400004] 0x27a50004 addiu $5, $29, 4 ; addiu $a1, $sp, 4 # argv [0x00400008] 0x24a60004 addiu $6, $5, 4 ; addiu $a2, $a1, 4 # envp [0x0040000c] 0x00041080 sll $2, $4, 2 ; sll $v0, $a0, 2 [0x00400010] 0x00c23021 addu $6, $6, $2 ; addu $a2, $a2, $v0 [0x00400014] 0x0c000000 jal 0x00400020 [main] ; jal main [0x00400018] 0x3402000a ori $2, $0, 10 ; li $v0 10 [0x0040001c]
0x0000000c syscall
Operating System
User
Operating System
Hardware
Virtual Environments
Operating Systems make the computer applications organized
• Hallway
• Desk
• File Cabinet
• Book Shelf
Virtual Environments
You’ve seen Operating Systems already:
• Windows whatever
• UNIX
• Mac
Usually work with WIMPs
(Windows, Icons, Menus, Pointers)
Booting up
• If the OS is the program that runs the other programs, how does the OS program get loaded and run in the first place?
• When you turn on the computer, it runs a hardwired program called bootstrap code that loads the OS.
OS Services
1. Provides access to software- Gives interface to user- Knows how to load applications into memory- Provides other communication between the
user and the application
OS Services
2. Provides a secure computing environment- Security for a system (logins and passwords)- Security for internal files and functions(You can’t erase my files; A program crash won’t crash the whole computer)- Security from hardware failure (tries to protect you from crashes with backup measures)
OS Services
3. Provides a file system
public_html
cps1 index.html<HTML>
My Homepage
images wedding
index.html<HTML>My CPS1Homepage
Lab 1 Comp.gif GuestlistSpreadsheet
OS Services4. Provides for Multiprogramming
(Multitasking)A process is a program in some state of
execution.Many can be running at once, while the
processor is waiting on one process, it runs a second.
It may also interrupt a process because of error or just to give another process a chance to run.
More on MultiprogrammingOS
Process 1
RegisterValues
Printer
Process 2
RegisterValues
Disk A
Process 3
RegisterValues
Disk A
Print a file
Read from Disk
More on Multiprogramming
• Several programs are competing for processor time, memory, use of devices, etc…
• OS is the manager that says who gets what
• OS must be programmed to avoid problems…
Multiprogramming Potential Problems
• Starvation – one process never gets the chance to get a resource
• Deadlock – every process waiting for something, and none can run
• Dirty Data – if more than one process is accessing a piece of data, there can be problems
Data Sharing
x = 4;
x = x + 1;
print x;
Shared integerx
x = x + 6;
Conclusion
• Operating Systems provide a bridge between user and computer
• They give access to computer functionality
• They provide security
• They provide file systems
• They manage multiprocessing and resource allocation