Hardware Computer

A Computer consist of CPU or Central Processing Unit or usually we just call it Processor because main part of unit is processor, Cable, Monitor or Display, Mouse and keyboard.

A central processing unit (CPU) is an electronic circuit that can execute computer programs. This broad definition can easily be applied to many early computers that existed long before the term "CPU" ever came into widespread usage. The term itself and its initialism have been in use in the computer industry at least since the early 1960s (Weik 1961). The form, design and implementation of CPUs have changed dramatically since the earliest examples, but their fundamental operation has remained much the same.

Early CPUs were custom-designed as a part of a larger, sometimes one-of-a-kind, computer. However, this costly method of designing custom CPUs for a particular application has largely given way to the development of mass-produced processors that are suited for one or many purposes. This standardization trend generally began in the era of discrete transistor mainframes and minicomputers and has rapidly accelerated with the popularization of the integrated circuit (IC). The IC has allowed increasingly complex CPUs to be designed and manufactured to tolerances on the order of nanometers. Both the miniaturization and standardization of CPUs have increased the presence of these digital devices in modern life far beyond the limited application of dedicated computing machines. Modern microprocessors appear in everything from automobiles to cell phones to children's toys.

In computing, a mouse (plural mouses, mice, or mouse devices) is a pointing device that functions by detecting two-dimensional motion relative to its supporting surface. Physically, a mouse consists of an object held under one of the user's hands, with one or more buttons. It sometimes features other elements, such as "wheels", which allow the user to perform various system-dependent operations, or extra buttons or features can add more control or dimensional input. The mouse's motion typically translates into the motion of a pointer on a display, which allows for fine control of a Graphical User Interface.

The name mouse, originated at the Stanford Research Institute, derives from the resemblance of early models (which had a cord attached to the rear part of the device, suggesting the idea of a tail) to the common mouse.

The first marketed integrated mouse – shipped as a part of a computer and intended for personal computer navigation – came with the Xerox 8010 Star Information System in 1981. However, the mouse remained relatively obscure until the appearance of the Apple Macintosh; in 1984 a prominent PC columnist commented the release of this new computer with a mouse: “There is no evidence that people want to use these things.”

A mouse now comes with most computers and many other varieties can be bought separately.

A visual display unit, often called simply a monitor or display, is a piece of electrical equipment which displays images generated from the video output of devices such as computers, without producing a permanent record. Most newer monitors typically consist of a TFT LCD, with older monitors based around a cathode ray tube (CRT). The monitor comprises the display device, simple circuitry to generate and format a picture from video sent by the signals source, and usually an enclosure. Within the signal source, either as an integral section or a modular component, there is a display adapter to generate video in a format compatible with the monitor.
Performance measurements

The performance parameters of a monitor are:

1. Luminance, measured in candelas per square meter (cd/m²).
2. Viewable image size, measured diagonally. For CRTs the viewable size is typically one inch (25 mm) smaller than the tube itself.
3. Display resolution, the number of distinct pixels in each dimension that can be displayed. Maximum resolution is limited by dot pitch.
4. Dot pitch, describes the distance between pixels of the same color in millimeters. In general, the smaller the dot pitch (e.g. 0.24 mm), the sharper the picture will appear.
5. Refresh rate, the number of times in a second that a display is illuminated. Maximum refresh rate is limited by response time.
6. Response time, the amount of time a pixel in a monitor takes to go from active (black) to inactive (white) and back to active (black) again. It is measured in milliseconds (ms). Lower numbers mean faster transitions and therefore fewer visible image artifacts.
7. Contrast ratio, the contrast ratio is defined as the ratio of the luminosity of the brightest color (white) to that of the darkest color (black) that the monitor is capable of producing.
8. Power consumption, measured in watts (W).
9. Aspect ratios, which is the horizontal size compared to the vertical size, e.g. 4:3 is the standard aspect ratio, so that a screen with a width of 1024 pixels will have a height of 768 pixels. A widescreen display can have an aspect ratio of 16:9, which means a display that is 1024 pixels wide will have a height of 576 pixels.
10. Viewing angle, the ability to be seen from an angle without excessive degradation to the image, measured in degrees horizontally and vertically.

Cable in computer is used for connected part of the computer, we usually call it port I/O. Memory-mapped I/O (not to be confused with memory-mapped file I/O) uses the same address bus to address both memory and I/O devices, and the CPU instructions used to access the memory are also used for accessing devices. In order to accommodate the I/O devices, areas of CPU's addressable space must be reserved for I/O rather than memory. The reservation might be temporary—the Commodore 64 could bank switch between its I/O devices and regular memory—or permanent. Each I/O device monitors the CPU's address bus and responds to any CPU's access of device-assigned address space, connecting the data bus to a desirable device's hardware register.

Port-mapped I/O uses a special class of CPU instructions specifically for performing I/O. This is generally found on Intel microprocessors, specifically the IN and OUT instructions which can read and write a single byte to an I/O device. I/O devices have a separate address space from general memory, either accomplished by an extra "I/O" pin on the CPU's physical interface, or an entire bus dedicated to I/O.

A device's direct memory access (DMA) is not affected by those CPU-to-device communication methods, especially it is not affected by memory mapping. This is because, by definition, DMA is a memory-to-device communication method, that bypasses the CPU.

Hardware interrupt is yet another communication method between CPU and peripheral devices. However, it is always treated separately for a number of reasons. It is device-initiated, as opposed to above CPU-initiated methods. It is also unidirectional, as information flows only from device to CPU. Lastly, each interrupt line carries itself only one bit of information with a fixed meaning, namely "there is an interrupt".

In computing, a keyboard is an input device, partially modeled after the typewriter keyboard, which uses an arrangement of buttons or keys, which act as electronic switches. A keyboard typically has characters engraved or printed on the keys and each press of a key typically corresponds to a single written symbol. However, to produce some symbols requires pressing and holding several keys simultaneously or in sequence. While most keyboard keys produce letters, numbers or signs (characters), other keys or simultaneous key presses can produce actions or computer commands.

In normal usage, the keyboard is used to type text or numbers into a word processor, text editor or other program. In a modern computer, the interpretation of keypresses is generally left to the software. A computer keyboard distinguishes each physical key from every other and reports all keypresses to the controlling software. Keyboards are also used for computer gaming, either with regular keyboards or by using special gaming keyboards, which can expedite frequently used keystroke combinations. A keyboard is also used to give commands to the operating system of a computer, such as Windows' Control-Alt-Delete combination, which brings up a task window or shuts down the machine.

TYPES OF KEYBOARDS

1. QWERTY Keyboard - Developed by Sholes in 1868 and is now the official standard of computer keyboards [ISO9995]. The layout of the QWERTY keyboard was designed for two finger typing and was designed to help prevent stuck keys. Now with new technology, stuck keys are no longer an issue; and with the position of the keys, the hands are held close together helping to cause Carpal Tunnel Syndrome. Given all the above problems, this is the most widely used keyboard because the lack of options, can be used without training, is used because of the difficulty of having to teach a different keyboard, and is cheap and easy to find.
2. Dvorak Keyboard - Developed by Dr. August Dvorak in 1936 as a solution to the outdated QWERTY keyboard. The layout of the keys on this keyboard make it easier and faster to type on when compared with other keyboards.
3. Chiclet Keyboard - Very small keyboard that was introduced with the PC Jr. with small keys spread out.