Transcript Chapter 2

Chapter 2
Operating Systems: Software in
the Background
Types of Software

Systems software
– programs related to coordinating computer
operations
– includes operating systems, language
translators, and utility programs

Application software
– software designed to accomplish a specific
task
– includes word processors, electronic
spreadsheets, etc.
What is an operating system?


The OS is a set of programs that
controls access to the hardware and
software resources of the computer.
kernel - the part of the OS that
supervises the overall operation of the
OS
– resident when computer is on (stored in
main memory)
Booting the system


When the computer it turned on, the
resident portions of the OS must be
loaded into main memory from the hard
disk.
A small program in ROM makes internal
hardware checks then starts the booting
process.
Popular operating systems

PC’s
– MS Windows
– Mac OS
– Linux - Unix-like system for PC’s

Multiuser systems
– Unix - not tied to a specific platform,
primary OS for the Internet
Terms

platform - combination of hardware and
OS used by a computer
– software is designed for a specific platform


prompt - a signal displayed on screen to
indicate that the system is waiting for a
command or input
icon - a picture that represents a
program, hardware device, or data
object (file)
More terms


menu - a list of options from which a
command can be selected
operating environment (shell) - a
program that overlays a program (often
an OS) to provide a more user friendly
interface
Operating System Functions

Management of the computer’s hardware
resources
– multiprogramming - single CPU runs two or
more programs concurrently
• time sharing - special form of multiprogramming
in which each user is allotted a time slice
– multiprocessing - multiple CPUs run
programs simultaneously
– virtual memory - currently active part of
program in memory, the rest on disk,
swapped in and out as needed
Operating System Functions

Execution and provision of services for
application software
– providing access to peripherals
• spooling - print jobs are written temporarily to
disk until the printer is ready
– retrieval of files for use
– allocating space for and storing files
Operating System Functions


Establishment of a user interface - the way a
user communicates with a program
2 major types for operating systems
– command line interface
• text-based, older, harder to learn
• MS-DOS, Unix, Linux
– graphical user interface
• use icons and menus to allow command input,
popular interface for PC’s, easy to learn
• Windows, Mac OS
Utility programs


some may be included with the OS
file manager - organizes files for easy
access
– provides the ability to display, copy, name,
delete, and move files
– format and copy disks

backup and restore
– duplication of important materials for safe
storage
More utility programs

disk defragmentation
– reorganization of files on disk to improve
system performance

file compression
– programs to reduce the size of files for
storage or transmission purposes

device driver
– program that makes it possible for the OS
to communicate with peripheral devices