Transcript Computer concepts - UTRGV Faculty Web

Operating Systems
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Computer Science
Software
Operating Systems
System software
Utilities
Software
Application software
System software: programs that manage the computer resources and
provide an interface to application software and users. For example,
operating systems, antivirus, compilers, etc.
Application software: programs that help the user to perform specific
tasks. For example, word processors, spreadsheets, web browsers, etc.
Operating System (OS)
The OS is the most important program running
on a computer because it controls all activities
that take place within a computer system.
Some popular OS for personal computers are:
• Windows Vista, 7, 8, etc.
• Linux
• Mac OS
• UNIX
Main tasks
The main tasks of an OS are:
• Provide a user interface.
• Provide an application software interface.
• Coordinate activities among the computer
resources.
User interface
The user interface facilitates the interaction
between the user and the computer system.
• Command-line: users must enter commands
at a prompt.
• Menu-driven: users select commands from a
menu.
• Graphical User Interface (GUI): users use
windows, dialog boxes, menus, etc. to
interact.
Application software interface
Application software access resources by making
requests for services to the OS through
application program interfaces (API).
If an application program needs a resource or
service it requests it from the OS.
Typically, application software cannot access
computer resources directly.
Resources management
Some of the resources that an OS must manage
are:
• Memory.
• Processor.
• Storage.
• Peripheral devices.
Resources management (cont.)
Memory:
• Ensures efficient use of RAM
• Implements virtual memory (VM)
Processor:
Allocates the CPU for a small amount of time to
each program running on the system so each
one of them can perform its task.
Resources management (cont.)
Storage:
Maintains the file system.
Allocates space on storage devices.
Manages access to files.
Peripheral devices:
Handles input and output from and to
peripheral devices attached to the
computer.This is typically done through device
drivers.
OS Categories
One way to classify OS is:
• Single-user: only one person can access the
computer at any moment.
• Multiple-user: many users can access the
system at the same time.
• Network: many users can access the network.
OS Functions
OS can allow the system to perform multiple
tasks simultaneously at different levels:
• Multitasking: several tasks can be executed
simultaneously by a single CPU.
• Multithreading: several parts of a single task
can be executed simultaneously by a single
CPU.
• Multiprocessor: several tasks can be executed
simultaneously by several CPUs.
The boot process
When the computer is powered on the CPU accesses
the ROM to execute the BIOS that:
• Runs the POST (Power On Self Test) to ensure all the
computer components are operational.
• Executes the bootstrap loader. This is a program that
loads the OS from a storage device (hard disk drive,
CD/DVD drive, flash drive, etc.) onto RAM. Once the
OS has been loaded it is given the control of the
computer.
Recovery (boot) disk: contains the basic system files that will
start the computer when there is a problem with the installed
OS.
Utility software
These are programs designed to help maintain
the system. Some utility programs have been
integrated into the OS.
• File managers: allow the user to perform
operations on files or folders such as create, open,
edit, view, print, rename, move, copy, delete, etc.
• Disk defragmenters: improve the system’s
performance.
• Disk checkers: find and fix disks’ bad sectors.
Utility software (cont.)
• Backup: allow the user to save their files (pictures,
videos, homework, etc.).
• Anti-virus: protects the system from malware
(programs that can harm a computer system).
• Data compression: allows the user to put several
files in a compressed folder so that it can be attached
to an email for example.
• Text editors: allow the user to create/modify plain
text.