Chapter 6 - OS

operating system (OS)

System software that provides an INTERFACE between the user or application program AND the computer hardware.

4 MAIN TASKS: 1) Provide user Interface.
2) Offer System Security and Protection.
3) Manage Resources Efficiently.
4) Use Resources Safely

AKA The most important software on a computer!

OS manages:
1) the hardware
2) the software resources (user wants resources, the OS delivers)
3) the services computer programs want

Found in lecture Chapter 6 Part 1 - Operating Systems

4 main tasks of OS

1) Provide User Interface
2) Offer System Security and Protection (OS acts like a security guard)
3) Manage Resources Efficiently
4) Use Resources Safely

Found in lecture Chapter 6 Part 1 - Operating Systems

Why do we want an interface between the user and the hardware?

-to hide hardware details
-to create a user-friendly environment
-to prevent damage to system (hardware and data)

Found in lecture Chapter 6 Part 1 - Operating Systems

What are some well-know operating systems?

Desktops/Laptops: Linux, MacOS, Windows

Mobile: Apple iOS, Google Android

Found in lecture Chapter 6 Part 1 - Operating Systems

GUI

Graphical User Interface

User interfaces today are graphical (as users found text interface "cumbersome"). However, text based interface can be very efficient.

Found in lecture Chapter 6 Part 1 - Operating Systems

superusers

user(s) who have more privileges (admin) than others

privileged users, usually computer center employees, with the ability to access and
maintain password files

Found in lecture Chapter 6 Part 2 - Operating Systems

process

a program in execution

Found in lecture Chapter 6 Part 2 - Operating Systems

fundamental OS task

process management

Found in lecture Chapter 6 Part 2 - Operating Systems

running state

the process is executing instructions

Found in lecture Chapter 6 Part 2 - Operating Systems

ready state

the process is runnable (ready to run), but not running
process is waiting in ready queue

Found in lecture Chapter 6 Part 2 - Operating Systems

blocked/waiting state

the process is waiting for some event to occur

Found in lecture Chapter 6 Part 2 - Operating Systems

new state

the process is being created by the OS

Found in lecture Chapter 6 Part 2 - Operating Systems

exit state

the OS is cleaning up a terminating process

Found in lecture Chapter 6 Part 2 - Operating Systems

time slice

process moves from RUNNING to READY
occurs when process has run for a MAX length of time

exists for processes "hogging" the CPU
process kicked off processor (process goes from RUNNING back to READY)

if SMALL time slice -> HUGE overhead costs (to move process from ready to running back to ready; think of OS tables that need to be updated / registers that get changed)

if LARGE time slice -> system response time is SLOW (turn around time for response gets too slow; users need to wait longer to get processor time)

Found in lecture Chapter 6 Parts 2 and 3 - Operating Systems

ready queue

line of processes ready to run

Found in lecture Chapter 6 Part 2 - Operating Systems

virtual memory

"virtualizes" memory/RAM locations (abstraction)

think of VM as "simulated physical memory (RAM)"

Found in lecture Chapter 6 Part 3 - Operating Systems

I/O intensive process

process is often BLOCKED

Found in lecture Chapter 6 Part 3 - Operating Systems

compute intensive process

process is mainly RUNNING or READY

Found in lecture Chapter 6 Part 3 - Operating Systems

deadlock

when two or more processes are permanently blocked on each other

one way to resolve = Deadlock Prevention
if process can't get everything it needs, it gets nothing

other types of deadlocks (and solutions) exist

Found in lecture Chapter 6 Part 3 - Operating Systems

processor utilization

percentage of time that the processor is busy

Found in lecture Chapter 6 Part 3 - Operating Systems

What does the OS provide?

- Scheduler
- Memory Managers (Loaders, Garbage collectors, Linkers)
- Information Managers (File systems, Database systems)
- Language Support (Interpreters, Compilers, Assemblers)
- I/O manager (Keyboard, printer, network connection)
- Utilities (Text editors, graphics routines).

Found in lecture Chapter 6 Part 1 - Operating Systems

example OS commands

-Load Program
-Run Program
-Save info to file/directory
-Retrieve previously stored file
-List all files for user
-Delete file
-Rename file
-Copy files from one I/O device to
another
-Print file on specified I/O device
-Establish network connection
-Let user set password
-Let user change password
-Relay memory usage
-Relay data storage usage