1. Operating Systems: Software in the Background
Chapter 2
Operating Systems: Software in the Background

2. Types of Software Systems software Application 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.

3. 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)

4. 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.

5. 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

6. 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)

7. 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

8. 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

9. 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

10. 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

11. 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

12. More utility programs disk defragmentation file compression
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