OPERATING SYSTEM NOTES
An operating system is a collection of integrated computer programs that provide recurring services to other programs or to the user of a computer. These services consist of disk and file management, memory management, and device management. In other words, it manages CPU operations, input/output activities, storage resources, diverse support services, and controls various devices.
Operating system is the most important program for computer system. Without an operating system, every computer program would have to contain instructions telling the hardware each step the hardware should take to do its job, such as storing a file on a disk. Because the operating system contains these instructions, any program can call on the operating system when a service is needed. Examples include:
DOS - Disk Operating System - one of the first operating systems for the personal computer. When you turned the computer on all you saw was the command prompt which looked like c:\ >. You had to type all commands at the command prompt which might look like c:\>wp\wp.exe. This is called a command-line interface. It was not very "user friendly"
Windows - The Windows operating system, a product of Microsoft, is a GUI (graphical user interface)operating system. This type of "user friendly" operating system is said to have WIMP features:
UNIX - Linux (the PC version of UNIX) - UNIX and Linux were originally created with a command- line interface, but recently have added GUI enhancements.
Firmware /stored logic
This is the combination of persistent memory and program code and data stored permanently on electronic chips. The firmware contained in these devices provides the control program for the device.
Firmware is held in non-volatile memory devices such as ROM, EPROM, or flash memory. They hold operating systems, utility programs, language processors etc.
Utility software is designed to help analyze, configure, optimize or maintain a computer. A single piece of utility software is usually called a utility or tool. Utility software usually focuses on how the computer infrastructure (including the computer hardware, operating system, data storage and application software operates)
Utility software categories
This software is used to establish communication between two or more computers by linking them using a communication channel like cables to create a computer network. It enables the exchange of data in a network as well as providing data security. Networking software may come as independent software or integrated in an operating system. Examples include: novel Netware, windows NT etc.
When computers communicate to one another, they need networking software often referred to as a protocol.
A protocol is a set of rules that govern how data packets move from one computer to another on a network connection.
This is computer software designed to help the user perform a specific task. Examples include enterprise software, accounting software, office suites, graphics software and media players. This book will mostly feature office suites.
Classification according to acquisition
In-house developed software
These are programs designed to meet a specific user’s needs. In this situation, a system analyst studies an existing system (most likely manual) and together with a programmer, they make a new computerized system to fit the needs of their client. For example, a school can hire a computer analyst to design a program that can be used to produce report cards.
Vendor off-the-shelf software
This kind of software is developed by software engineers, packaged and then made available for purchase through a vendor, a distributor or directly from the developer. Several applications may be bundled together to form a suite e.g. Microsoft office, Lotus suite, Corel word perfect, quick books etc.
Advantages of standard software over in-house developed programs are:
Disadvantages of Off-the-Shelf software
Classification according to End-User-License:
This is software that is available for use at no cost or for an optional fee, but usually with one or more restricted usage rights.
Example: Adobe reader, Adobe flash player, Ubuntu operating system, Rising Antivirus, VLC media player etc. This software is sourced for free but they are vulnerable to computer viruses or can carry a virus unto your computer.
Shareware (also termed trialware or demoware) is proprietary software that is provided to users without payment on a trial basis and is often limited by any combination of functionality, availability (it may be functional for a limited time period only), or convenience (the software may present a dialog at startup or during usage, reminding the user to purchase it; "nagging dialogs"). Shareware is often offered as a download from an Internet website or as a compact disc included with a periodical such as a newspaper or magazine. The rationale behind shareware is to give buyers the opportunity to use the program and judge its usefulness before purchasing a license for the full version of the software. Firms with superior software thus have an incentive to offer samples, except if their product is already well known, or if they do not want to be listed in direct competition with other products on shareware repositories.
Proprietary software is computer software licensed under exclusive legal right of the copyright holder. The licensee is given the right to use the software under certain conditions, while restricted from other uses, such as modification, further distribution, or reverse engineering.
Free and open-source software (FOSS)
Free and open-source software (FOSS) or free/libre/open-source software (FLOSS) is software that is both free software and open source. It is liberally licensed to grant users the right to use, copy, study, change, and improve its design through the availability of its source code.
This approach has gained both momentum and acceptance as the potential benefits have been increasingly recognized by both individuals and corporations.
Open-source software (OSS)
Open-source software (OSS) is computer software that is available in source code form: the source code and certain other rights normally reserved for copyright holders are provided under an open-source license that permits users to study, change, improve and at times also to distribute the software.
Criteria for selecting a computer system
When purchasing a computer hardware or software, consider a number of requirements necessary to fit your needs and costs.
1. Microprocessor type and speed- the speed and processing power of a computer depends on the type of CPU and its clock speed. Consider microprocessors with high cache memory and faster clock speeds since they can be able to run a variety of tasks without strain. Intel Duo Core and AMD Duron are the latest for PCs.
2. Memory capacity- Consider the capacity of your memory since higher memories creates good performance of your computer. Check whether it’s static or dynamic, DDR or SDR, empty memory slots on the motherboard and whether they are up gradable with other installed modules.
3. Warranty- A warranty is an agreement between the buyer and the seller that spells terms and conditions of, after selling a product incase of failure or malfunction. A good warranty should cover the following:
Whether it’s a Branded or a clone- a clone is a hardware or software system that is designed to mimic another system whilst a branded computer is a computer whose parts are made by one company copyrighted and standardized, they are more expensive than clones but are of high quality. Examples: Dell, Acer, Compaq, HP, Apple etc.
Size- Portable computers are more expensive than desktops because of the complexity of technology used to make them.
5. Upgradeability and Compatibility- Upgradeability is the ability of a system to embrace to new forms of technology available in the market and Compatibility is the ability of a system to run in more than one different system families. For example: a computer that can run on windows, MAC, Ubuntu, etc operating systems.
6. Portability- Consider your user needs and decide whether you need a computer that you can easily carry from one place to another or fixed in one place. In this case, a palmtop or a laptop and a desktop are convenient respectively.
7. User Needs- Value your user needs and any other needs you will use this computer for. If you want a variety of tasks, then try a general purpose computer.
8. Monitors- Check for video adaptors, resolution, power consumption and saving, technology used to manufacture them (TFT, Gas Plasma, CRT etc)
9. Multimedia Capabilities – This is the ability to support multimedia functions like: sound card, TV card, SVGA monitor, CD/DVD drives etc.
10. Cabling- check whether the ports are user friendly, wireless or bound and strategically positioned on the system unit which might be a tower or a desktop type.
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