A process is a computer program running on a computer.
A computer program in simple terms is an executable set of commands for the computer to perform. A process is an actively running program which may or may not be running in the background. A program running in the background is one that the computer user may not be aware of, but it may be providing useful services such as an ability to connect to other computers.
This is the “brain” of the computer ; it reads and executes program instructions, performs calculations, and makes decisions .
The CPU is responsible for storing and retrieving information on disks and other media. It also handles information on from one part of the computer to another like a central switching station that directs the flow of traffic throughout the computer system.
A silicon chip that contains a CPU. In the world of personal computers, the terms microprocessor and CPU are used interchangeably .
It's sometimes called a logic chip . It is the "engine" that goes into motion when you turn your computer on.
At the heart of all personal computers and most workstations sits a microprocessor. Microprocessors also control the logic of almost all digital devices, from clock radios to fuel-injection systems for automobiles.
Three basic characteristics differentiate microprocessors:
Instruction set : The set of instructions that the microprocessor can execute.
bandwidth : The number of bits processed in a single instruction.
clock speed : Given in megahertz (MHz), the clock speed determines how many instructions per second the processor can execute.
Data is a collection of unorganized facts that can include words, numbers, pictures, sounds, and videos.
A program is a series of instructions that tells a computer how to perform the tasks necessary to process data into information. Programs are kept on storage media such as a floppy disk, hard disk, CD-ROM, or DVD-ROM.
Many input devices use an electronic pen instead of keyboard or mouse for input. Some of there devices require you to point to onscreen objects with the pen ;others allow you to input data using drawings, handwriting, and other symbols that are written with the pen on a surface.
Instead of touching the screen with your finger to interact with the computer, you press the light pen against the surface of the screen or point the light pen at the screen and then press a button on the pen.
A graphics tablet , also called a digitizer or digitizing tables , consists of a flat, rectangular, electronic plastic bond used to input drawings, sketches, or other graphical data.
Each location on the graphical tablet corresponds to a specific location on the screen. When you draw on the tablet with either an electronic pen or a puck, the tablet detects and converts the movements into digital signals that are sent into the computer.
A mechanical mouse has ball mechanism on the bottom, a trackball is a station- aryl pointing device with a ball mechanism on its top .
Although it shares characteristic with a mouse, a trackball is not as accurate as a mouse .A trackballs ball mechanism also requires frequent cleaning because it picks up oils from your fingers and dust from the environment.
Digital camera allows you to take pictures and store the photographed images digitally instead of on traditional film.
With some digital cameras, you down l oad , or transfer a copy of, the stored pictures to your computer by connecting a cable between the digital camera and your computer and using special software included with the camera.
The three basic types of digital cameras are studio cameras, field cameras, and point-and shoot- cameras.
A mouse that has a rubber or metal ball on its underside is called a mechanical mouse . When the ball rolls in a certain direction, electronic circuits in the mouse translate the movement of the mouse into signals that are sent to the computer.
Another type of mouse, called an optical mouse , has no moving mechanical parts inside; instead it uses devices that emit light to detect the mouse’s movement.
Handheld scanners use the same basic technology as a flatbed scanner, but rely on the user to move them instead of a motorized belt. This type of scanner typically does not provide good image quality. However, it can be useful for quickly capturing text.
Drum scanners are used by the publishing industry to capture incredibly detailed images. They use a technology called a photo multiplier tube (PMT). In PMT, the document to be scanned is mounted on a glass cylinder. At the center of the cylinder is a sensor that splits light bounced from the document into three beams. Each beam is sent through a color filter into a photo multiplier tube where the light is changed into an electrical signal.
A standard computer keyboard sometimes is called a QWERTY keyboard because of the layout of its typing area.
Pronounced KWER-tee, this keyboard layout is named after the first six leftmost letters on the top alphabetic line of the keyboard. Because of the way the keys are organized, a QWERTY keyboard might limit your typing speed.
Users running game software such as a driving of flight simulator may prefer to use a joystick as their pointing device.
A joystick is a vertical lever mounted on a base. You move the lever in different direction to control the actions of a vehicle or player. The lever usually includes buttons called triggers that you can press to activate certain events.
0utput is data that has been processed into a useful form called information.
Computers generate several types of output, depending on the hardware and software being used and the requirements of the user. You may choose to display or view this output on a monitor, print it on a printer, or listen to it through speakers or a headset.
Is music, speech, or any other sound. Recall that sound waves, such as the human voice or music, are analog .
To store such sounds, a computer converts the sounds from a continuous analog signal into a digital format. Most output devices require that the computer convert the digital format back into analog signals.
Video consists of images that are played back at speeds that provide the appearance of full motion.
Video often is captured with a video input devices such as a camera or VCR. A video capture card converts an analog video signal into a digital that a computer can understand. The digital signal then is stored on the computer’s hard disk.
An LCD projector , which uses liquid crystal display technology, attaches directly to a computer and uses its own light source to display the information shown on the computer screen. Because LCD projectors tend to produce lower-quality images, some users prefer to use a DLP projector for shaper, brighter images.
A liquid crystal display consists of an array of tiny segments (called pixels ) that can be manipulated to present information.
A CRT monitor , or monitor is a display device that consists of a screen housed in a plastic or metal case.
A color monitor display text, graphics and video information in color. Color monitor are used widely with all types of computers because most of today’s software is designed to display information in color.
Gas plasma monitors use gas plasma technology, which substitutes a layer of gas the liquid crystal material in an LCD monitor.
When voltage is applied, the gas glows and produces the pixels that form an image. Gas plasma monitors offer larger screen sizes and higher display quality than LCD monitors but are much more expensive.
The quality of a monitor’s display depends largely on its:
The resolution or sharpness and clarity, of a monitor are related directly to the number of pixels it can display. Resolution is expressed as two separate numbers: the number of columns of pixels and the number of rows of pixels a monitor can display.
Pitch is a measure of image clarity. The dot pitch is the vertical distance between each pixel on a monitor. The smaller the distance between the pixels, the sharper the displayed image.
A monitor’s refresh rate should be fast enough to maintain a constant, flicker-free image. A slower refresh rate causes the image to fade and then flicker as it is redrawn, which can headaches for user. Refresh rate is measured according to hertz , which is the number of times per second the screen is redrawn.
Storage also called secondary storage, auxiliary storage, or mass storage . Holds items such as data, instruction, and information for future use.
Think of storage as a filling cabinet used to hold file folder, and memory as the top of your desk. When you need to work with a file, you remove it from the filling cabinet (storage) and place it on your desk (memory). When you are finished with the file, you return it to the filling cabinet (storage).
The size, or capacity , of storage devices, is measured by the number of bytes (characters). For example, a typical floppy disk can store 1.44 MB of data (approximately 1,440,000 bytes) and a typical hard disk can store 8GB of data (approximately 8,000,000,000 bytes).
Memory , which is composed of one or more chips on the motherboard, holds data and instruction while the CPU is processing them.
The two basic type of memory are volatile and nonvolatile. The contents of volatile memory , such as RAM are lost (erased) when the power to the computer is turned of. The contents of nonvolatile memory , however, are not lost when power is removed from the computer. For example, once instruction has been record onto a nonvolatile ROM chip, they usually cannot be erased or change, and the contents of the chips are not erased when power is turned off.
A floppy disk , or diskette , is a portable, inexpensive storage medium that consists of a thin, circular, flexible plastic disk with a magnetic coating enclosed in a square-shaped plastic shell).
In the early 1970s, IBM introduced the floppy disk a new type or storage. Because these early 8-inch wide disk had flexible plastic cover, many users referred to them as floppies. The next generation of floppies looked much the same, but was only 5.25-inches wide. Today, the most widely used floppy disk is 3.5-inches wide. The flexible cover of the earlier floppy disk has been replaced with a rigid plastic outer cover. Thus, although today’s 3-5 inches disk are not at all floppy. The term floppy disk still used.
On a floppy disk, if the write protect notch is exposed, or open, the drive cannot write on the floppy disk. If the write-protect north is covered, or closed, the drive can write on the floppy disk. The write protect notch only affect the flopper disk drive’s capability of writing on the disk: a floppy disk drive car read from the floppy disk whether the write-protect notch is open or closed. Some floppy disk has a second opening on the opposite side of disk that does not have the small tab: this opening identifies the disk as a high-density floppy disk.
A floppy disk drive (FDD) is a device that can read from and write on a floppy disk. Desktop personnel computers usually have a floppy disk drive installed inside the system unit.
Floppy disk drive is downward compatible , which means they recognize and can use earlier media. Floppy disk drive is not upward compatible , however, which means they cannot recognize newer media. For example, a lower-density floppy disk drive cannot read from or write on a high-density floppy disk.
On any 3.5-inch floppy disk, a piece of metal called the shutter covers an opening in the rigid plastic shell. When you insert a floppy disk into a floppy disk drive, the drives slides shutter to the side to expose a portion of both sides of the floppy disk’s recording surface.
The read/write head is the mechanism that actually read items from a write items on the floppy disk. Figure 6-0 illustrates the steps for reading from and writing on a floppy disk. The average access time for current floppy disk drives to locate an item on the disk is 84 ms, or approximately 1/12 of a second.
A hard disk usually consist of several inflexible, circular disk, called platter, on which item are stored electronically.
The hard disk in most desktop personnel computer is housed inside the system unit. Such hard disk, which are not portable, are considered fixed disk.
A platter in a hard disk is made of aluminum, glass, or ceramic and is coated with a material that allow item to be magnetically recorded on it surface. On hard disk, the platter, the read/write heads, and the mechanism for moving the heads across the surface of the disk enclosed in a airtight, sealed case that protect the platters from contamination.