A computer is a programmable machine that receives input, stores and manipulates data, and provides output. It consists of basic components like a case, motherboard, processor, memory, drives, monitor, keyboard and mouse. Computers come in various sizes and types including desktops, laptops, and tablets. They can also be classified as mainframes, microcomputers, and supercomputers depending on their processing power and size.

1. A computer<br />A computer is a programmable machine that receives input, stores and manipulates data, and provides output in a useful format.<br />Computer ComponentsComputers come in all types and sizes. There are primarily two main sizes of computers. They are: Portable Desktop The portable computer comes in various sizes and are referred to as laptops, notebooks, and hand-held computers. These generally denote different sizes, the laptop being the largest, and the hand-held is the smallest size. This document will mainly talk about the desktop computer although portable computer issues are also discussed in various areas. Computer Components:Computers are made of the following basic components: Case with hardware inside: Power Supply - The power supply comes with the case, but this component is mentioned separately since there are various types of power supplies. The one you should get depends on the requirements of your system. This will be discussed in more detail laterMotherboard - This is where the core components of your computer reside which are listed below. Also the support cards for video, sound, networking and more are mounted into this board. Microprocessor - This is the brain of your computer. It performs commands and instructions and controls the operation of the computer. Memory - The RAM in your system is mounted on the motherboard. This is memory that must be powered on to retain its contents. Drive controllers - The drive controllers control the interface of your system to your hard drives. The controllers let your hard drives work by controlling their operation. On most systems, they are included on the motherboard, however you may add additional controllers for faster or other types of drives. Hard disk drive(s) - This is where your files are permanently stored on your computer. Also, normally, your operating system is installed here.CD-ROM drive(s) - This is normally a read only drive where files are permanently stored. There are now read/write CD-ROM drives that use special software to allow users to read from and write to these drives.Floppy drive(s) - A floppy is a small disk storage device that today typically has about 1.4 Megabytes of memory capacity.Other possible file storage devices include DVD devices, Tape backup devices, and some others. Monitor - This device which operates like a TV set lets the user see how the computer is responding to their commands.Keyboard - This is where the user enters text commands into the computer.Mouse - A point and click interface for entering commands which works well in graphical environments. ROM read-only memory: (computer science) memory whose contents can be accessed and read but cannot be changed.Random-access memory (RAM) is a form of computer data storage. Today, it takes the form of integrated circuits that allow stored data to be accessed in any order in a constant time, regardless of its physical location and whether it is related to the previous piece of data<br />Pronounced ramm, acronym for random access memory, a type of computer memory that can be accessed randomly; that is, any byte of memory can be accessed without touching the preceding bytes. RAM is the most common type of memory found in computers and other devices, such as printers.<br /> There are two different types of RAM: DRAM (Dynamic Random Access Memory) and SRAM (Static Random Access Memory). The two types differ in the technology they use to hold data, with DRAM being the more common type. In terms of speed, SRAM is faster. DRAM needs to be refreshed thousands of times per second while SRAM does not need to be refreshed, which is what makes it faster than DRAM. DRAM supports access times of about 60 nanoseconds, SRAM can give access times as low as 10 nanoseconds. Despite SRAM being faster, it's not as commonly used as DRAM because it's so much more expensive. Both types of RAM are volatile, meaning that they lose their contents when the power is turned off.<br />In common usage, the term RAM is synonymous with main memory, the memory available to programs. For example, a computer with 8MB RAM has approximately 8 million bytes of memory that programs can use. In contrast, ROM (read-only memory) refers to special memory used to store programs that boot the computer and perform diagnostics. Most personal computers have a small amount of ROM (a few thousand bytes). In fact, both types of memory (ROM and RAM) allow random access. To be precise, therefore, RAM should be referred to as read/write RAM and ROM as read-only RAM.<br />See the quot;
DRAM Memory Guidequot;
in the Quick Reference section of Webopedia. This Webopedia Quick Reference offers general information on the two types of RAM and provide an overview on the common modules of each type. <br /> See quot;
Tips to Fix a Slow Running Computerquot;
in the Quick Reference section of Webopedia.quot;
See also quot;
The Difference Between Laptop and Desktop Memoryquot;
in the Did You Know...? section of Webopedia.<br />Types of computer <br />Personal computers or microcomputers<br />Microcomputers are built to be used by one person. In fact when you talk about personal computers or its common acronym PC, you always mean microcomputers.<br />Types of mobile computers<br />If you prefer the laptop you’ll go for the mobile or portable system. Your notebook, a common name of laptop, has the advantage to have all the parts built together.<br />Types of mini computers<br /> <br />Apart the micro computers, you may consider three other types of computers: the minicomputers, the mainframes and the supercomputers.<br /> <br />Be advised that the name minicomputers does not mean it is slowest than your PC. Surely not! If you plan to build a home network the minicomputers can be used as a mid- range server to serve multiple users.<br /> <br />However with the mainframe you are able to build a large network for several hundred clients. You can process millions of transactions daily with the mainframe because of its high capacity. Most of enterprises such as large organizations, insurance businesses, industry, banking … usually use the mainframe for processing and storing enormous amounts of data every day.<br /> <br />The supercomputer is the fastest machine in the history of computer not only for its size but especially for its capacity. You won’t have to use this powerful system unless you are working with nuclear or aerodynamic companies for example.<br />Different Types of Computers<br />Electronics Classifieds Free Classifieds. Sell It Online. Sell Your Electronics For Free! www.Dealfish.com.ng<br />Durable computers? Get the world's leading computer brands at affordable prices now! www.druston.com.ng/computers<br />Buy Laptops Cheap Online Refurbished Laptops with Warranty Ship Direct to You from USA USAnotebook.com/Africa_laptops<br />A computer is one of the most brilliant inventions of mankind. Thanks to the computer technology, we were able to achieve an efficient storage and processing of data; we could rest our brains by employing computer memory capacities for storage of the information. Owing to computers, we have been able speed up daily work, carry out critical transactions and achieve accuracy and precision in work output. The computers of the earlier years were of the size of a large room and were required to consume huge amounts of electric power. However, with the advancing technology, computers have shrunk to the size of a small watch. Depending on the processing powers and sizes of computers, they have been classified under various types. Let us look at the classification of computers.<br />Different types of ComputersBased on the operational principle of computers, they are categorized as analog computers and hybrid computers.Analog Computers: These are almost extinct today. These are different from a digital computer because an analog computer can perform several mathematical operations simultaneously. It uses continuous variables for mathematical operations and utilizes mechanical or electrical energy.Hybrid Computers: These computers are a combination of both digital and analog computers. In this type of computers, the digital segments perform process control by conversion of analog signals to digital ones.Following are some of the other important types of computers.Mainframe Computers: Large organizations use mainframes for highly critical applications such as bulk data processing and ERP. Most of the mainframe computers have the capacities to host multiple operating systems and operate as a number of virtual machines and can thus substitute for several small servers.Microcomputers: A computer with a microprocessor and its central processing unit is known as a microcomputer. They do not occupy space as much as mainframes. When supplemented with a keyboard and a mouse, microcomputers can be called as personal computers. A monitor, a keyboard and other similar input output devices, computer memory in the form of RAM and a power supply unit come packaged in a microcomputer. These computers can fit on desks or tables and serve as the best choices for single-user tasks.<br />Personal computers come in a variety of forms such as desktops, laptops and personal digital assistants. Let us look at each of these types of computers.Desktops: A desktop is intended to be used on a single location. The spare parts of a desktop computer are readily available at relative lower costs. Power consumption is not as critical as that in laptops. Desktops are widely popular for daily use in workplaces and households.Laptops: Similar in operation to desktops, laptop computers are miniaturized and optimized for mobile use. Laptops run on a single battery or an external adapter that charges the computer batteries. They are enabled with an inbuilt keyboard, touch pad acting as a mouse and a liquid crystal display. Its portability and capacity to operate on battery power have served as a boon for mobile users.Personal Digital Assistants (PDAs): It is a handheld computer and popularly known as a palmtop. It has a touch screen and a memory card for storage of data. PDAs can also be effectively used as portable audio players, web browsers and smart phones. Most of them can access the Internet by means of Bluetooth or Wi-Fi communication.Minicomputers: In terms of size and processing capacity, minicomputers lie in between mainframes and microcomputers. Minicomputers are also called mid-range systems or workstations. The term began to be popularly used in the 1960s to refer to relatively smaller third generation computers. They took up the space that would be needed for a refrigerator or two and used transistor and core memory technologies. The 12-bit PDP-8 minicomputer of the Digital Equipment Corporation was the first successful minicomputer.Supercomputers: The highly calculation-intensive tasks can be effectively performed by means of supercomputers. Quantum physics, mechanics, weather forecasting, molecular theory are best studied by means of supercomputers. Their ability of parallel processing and their well-designed memory hierarchy give the supercomputers, large transaction processing powers.Wearable Computers: A record-setting step in the evolution of computers was the creation of wearable computers. These computers can be worn on the body and are often used in the study of behavior modeling and human health. Military and health professionals have incorporated wearable computers into their daily routine, as a part of such studies. When the users’ hands and sensory organs are engaged in other activities, wearable computers are of great help in tracking human actions. Wearable computers are consistently in operation as they do not have to be turned on and off and are constantly interacting with the user.These were some of the different types of computers available today. Looking at the rate of the advancement in technology, we can definitely look forward to many more types of computers in the near future. <br />