UNIT 3
OPERATING SYSTEM
4º E.S.O.
0.
SOFTWARE. CLASSIFICATION.
1.
THE OPERATING SYSTEM. FUNCTIONS.
1.1.
Functions. Estructure. Types.
1.2.
Software distribution.
0. EL SOFTWARE.
We can define software as the computer’s logical support, consisting of a set of logical components that make its operation possible. The operating system and the programs and applications we use are all software.
When a computer is turned on, the first software to start working is the BIOS. Next, the operating system is loaded and, finally the applications.
• System Software. This is a type of computer software which controls and coordinates the procedures and functions of computer hardware and applications. It allows harmonious computing coexistence by carrying out the man in the middle tasks which provide the platform onto which secondary software is installed and run.
System software can be categorized under the following:
- Operating system: to enable direct communication between hardware, system
programs and other applications.
- Device driver: to enable device communication with the OS and other applications.
- Utilities: to ensure optimum functionality of devices and applications.
• Application Software. This is a type of computer software meant to accomplish productive and meaningful tasks for the user. Every single application is designed with the end user in mind as contrasted with system and programming languages software, which are concerned with computer management and development.
• Programming Software. This is a set of tools used by programmers to create other software like Windows OS and Word processing. Also called languages, they are used to write source codes, debug errors, and maintain and create new software for computers.
• Communication software. Communication software is used to provide remote access to systems and exchange files and messages in text, audio and/or video formats between different computers or users.
This includes terminal
emulators, file transfer
programs, chat and instant messaging programs.
1. THE OPERATING SYSTEM. FUNCTIONS.
An Operating system (OS) is a software which acts as an interface between the end user and computer hardware. Every computer must have at least one OS to run other programs. An application like Chrome, MS Word, Games, etc. needs some environment in which it will run and perform its task.
The OS helps you to communicate with the computer without knowing how to speak the computer's language. It is not possible for the user to use any computer or mobile device without having an operating system.
Any type of computer system have four components: user, applications, operating system and hardware.
1.1.
Functions. Estructure. Types.
• Functions. In an operating system software performs each of the function:
- Process management. Process management helps OS to create and delete
processes. It also provides mechanisms for synchronization and communication among processes.
- Memory management. Memory management module performs the task of allocation and de-allocation of memory space to programs in need of this resources.
- File management. It manages all the file-related activities such as organization storage, retrieval, naming, sharing, and protection of files.
- Device Management. Device management keeps tracks of all devices. This
module also responsible for this task is known as the I/O controller. It also performs the task of allocation and de-allocation of the devices.
- I/O System Management. One of the main objects of any OS is to hide the
peculiarities of that hardware devices from the user.
- Secondary-Storage Management. Systems have several levels of storage which
includes primary storage, secondary storage, and cache storage. Instructions and data must be stored in primary storage or cache so that a running program can reference it.
- Security. Security module protects the data and information of a computer system against malware threat and authorized access.
- Command interpretation. This module is interpreting commands given by the
and acting system resources to process that commands.
- Networking. A distributed system is a group of processors which do not share memory, hardware devices, or a clock. The processors communicate with one another through the network.
- Job accounting. Keeping track of time & resource used by various job and users.
- Communication management: Coordination and assignment of compilers,
interpreters, and another software resource of the various users of the computer systems.
• Components. The components of an operating system all exist in order to make the different parts of a computer work together.
- Kernel. The kernel is the central component of a computer operating systems.
The only job performed by the kernel is to the manage the communication between the software and the hardware. A Kernel is at the nucleus of a computer. It makes the communication between the hardware and software possible. While the Kernel is the innermost part of an operating system, a shell is the outermost one.
- Memory management. This makes sure that a program does not conflict with memory currently being used by an additional program. Since programs time share, each program has to have independent access to memory. To puts it simply, the MMU is in charge of all aspects of memory management. It is normally integrated right into the CPU, although in some systems it takes up a separate IC (integrated circuit) chip.
- I/O Device Management. One of the important use of an operating system that
helps the user to hide the variations of specific hardware devices from the user. Functions of I/O management in the OS:
a) It offers buffer caching system.
b) It provides general device driver code.
c) It provides drivers for particular hardware devices.
d) It helps the user to know the individualities of a specific device. - File Management. A file is a set of related information
which is should define by its creator. It commonly represents programs, both source and object forms, and data. Data files can be numeric, alphabetic, or alphanumeric. The operating system has the following important given activities in connections with file management:
a) File and directory creation and deletion. b) For manipulating files and directories. c) Mapping files onto secondary storage. d) Backup files on stable storage media.
• Classification of operating systems.
- Multi-user: is the one that concede two or more users to use their programs at the same time. Some of O.S permits hundreds or even thousands of users simultaneously.
- Single-User: just allows one user to use the programs at one time.
- Multiprocessor: Supports opening the same program more than just in one
CPU.
- Multitasking: Allows multiple programs running at the same time.
- Single-tasking: Allows different parts of a single program running at any one time.
- Real time: Responds to input instantly.
- Time-Sharing. Time-sharing is a mechanism in which a task is given some time to execute.
- Distributed. The distributed operating system is a collection of independent computers and makes them appear to be a single computer.
1.2.
Software distribution.
Software Licensing is a critical component in letting others use, copy, modify, and distribute your software application. The actual software license itself is usually written in a legal agreement called a software license agreement, where the publisher grants a license to the end-user, who in turn agrees to the software
publisher’s terms of use.
The main categories of Software licenses are:
• Closed Source Licenses. Also sometimes known as proprietary licenses or commercial licenses, these are the license types that are usually (but not always) bought and sold. They typically do not allow modification of the program, or its distribution.
• Open Source Licenses. In general, open-source software licenses allow the end user to view and edit and distribute the software and the source code. There are a few different flavors of open source licenses giving more of less freedom on all of these attributes.
• Shareware is software that comes with permission to redistribute copies, but says that anyone who continues to use a copy is required to pay. Shareware is not free
software, or even semi-free. For most shareware, source code is not available; thus, the program cannot be modified. Shareware does not come with permission to make a copy and install it without paying a license fee, including for nonprofit activity. • Freeware. Like shareware, freeware is software available for download and distribution without any initial payment. Freeware never has an associated fee. Things like minor program updates and small games are commonly distributed as freeware. Though freeware is cost free, it is copyrighted, so other people can't market the software as their own.
• Free software is software that comes with permission for anyone to use, copy and distribute, either verbatim or with modifications, either gratis or for a fee. In particular, this means that source code must be available
1.3.
Software licences
.A software license is a document that provides legally binding guidelines for the use and distribution of software.
Software licenses typically provide end users with the right to one or more copies of the software without violating copyrights. The license also defines the responsibilities of the parties entering into the license agreement and may impose restrictions on how the software can be used. Software licensing terms and conditions usually include fair use of the software, warranties and disclaimers and protections if the software or its use infringes on the intellectual property rights of others.
Software licenses typically are either proprietary, free or open source, the distinguishing feature being the terms under which users may redistribute or copy the software for future development or use.
According to copyright law and type of licenses, software applications are grouped into:
• Closed source code, which is generally non-free. Its creator or publisher retains the intellectual property rights for it. Such software is, as a rule, distributed with a contract between the owner and user, the so-called end-user license agreement. It defines the non-negotiable terms under which the software is distributed. Without accepting these terms, end user can not use the software. One of the most widely known proprietary software pieces are Microsoft Windows, macOS, iTunes.
• Open source code. A software could be called open source in case its source code is publicly available and distributed for free for any field of endeavor. All derived works and modifications of such software should be distributed under the same
terms as the original license’s ones.
Open source software could be distributed under the following licenses:
- Non-protective licenses. These licenses do not protect the code from being used in non-open source apps and apply no restrictions on the derivatives.
- Protective licenses. Unlike non-protective ones, protective licenses force the author of derivatives or re-distributor of the software to open the modified code. Such licenses oblige the derivatives of copyleft license to be placed under copyleft too. The most popular copyleft license is General Public License (GPL).
It is sometimes referred to as a “viral” license due to its motto: “once free, always free”.
• Public domain software is any software that has no legal, copyright or editing restrictions associated with it. It is free and open-source software that can be publicly modified, distributed or sold without any restrictions.
- The GNU General Public License (GNU GPL or simply
GPL) is a series of widely-used free software licenses that guarantee end users the freedom to run, study, share, and modify the software.
- The GNU Lesser General Public License (LGPL) is a free-software license. The license allows developers and companies to use and integrate a software component released under the LGPL into their own (even proprietary) software without being required by the terms of a strong copyleft license to release the source code of their own components.
