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.
Carries out instructions and tells the rest of computer system what to do.
Sends command signals to the other components of the system.
Perform arithmetic calculations and data manipulation.
Holds data and instructions, which are in current use.
CONTROL UNIT (CU)
Directs the entire computer system to carry out stored program instructions.
Instructs the arithmetic logic unit which arithmetic operations or logical operation is to be performed.
ARITHMETIC LOGIC UNIT (ALU)
Executes arithmetic and logical operations.
Arithmetic operations include addition, subtraction, multiplication and division.
Logical operations compare numbers, letters and special characters.
Holds data and instructions for processing.
RAM (Random Access Memory) - used to store instructions and data needed while processing.
b) ROM (Read Only Memory) - ROM comes with instructions permanently stored inside and these instructions cannot be over-written by the computer’s CPU.
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.
In both cases, the higher the value, the more powerful the CPU.
For example, a 32-bit microprocessor that runs at 50MHz is more powerful than a 16-bit microprocessor that runs at 25MHz.
In addition to bandwidth and clock speed, microprocessors are classified as being either RISC (reduced instruction set computer) or CISC (complex instruction set computer).
WHAT IS INPUT?
Input is any data or instructions you enter into the memory of a computer.
Once input is in memory, the CPU can access it and process the input into output. Four types of input are data, programs, commands, and user responses.
4 TYPES OF INPUT
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.
4 TYPES OF INPUT (cont.)
A command is an instruction given to a computer program. Typing keywords or pressing special keys on the keyboard can issue commands.
A user response is an instruction you issue to the computer by replying to a question posed by a computer program, such as do you want to save the change you made?
An input device is any hardware component that allows you to enter data, programs, commands, and user responses into a computer.
Input devices include the keyboard , pointing devices, scanners and reading devices, digital cameras, audio and video input devices for physically challenged user.
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.
A light pen is a handheld input device that contains a light source or can detect light.
Some light pens require a specially designed monitor, while others work with a standard monitor.
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.
Many handheld computers also allow inputting data using an electronic pen (also called a stylus ) looks like a ballpoint pen but uses an electronic head instead of ink.
Pen computers use handwriting recognition software that translates the letters and symbols used in handwriting into character data that the computers can use.
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.
The mouse is the most widely used pointing device because it takes full advantage of a graphical user interface.
A mouse is an input device that is used to control the movement of the pointer on the screen and to make selections from the screen.
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.
Scanners have become an important part of the home office over the last few years. Scanner technology is everywhere and used in many ways:
Flatbed scanners , also called desktop scanners, are the most versatile and commonly used scanners. In fact, this article will focus on the technology as it relates to flatbed scanners.
Sheet-fed scanners are similar to flatbed scanners except the document is moved and the scan head is immobile. A sheet-fed scanner looks a lot like a small portable printer.
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.
KEYBOARD TYPES (cont.)
A keyboard with an alternative layout was designed to improve typing speed called the Dvorak keyboard (pronounced de-vor-zhak),
This type of keyboard places the most frequently typed letters in the middle of the typing area.
Despite the more logical design of the Dvorak keyboard, the QWERTY keyboard is more widely used.
A microphone is used to record sound. The sound is then saved as a sound file on the computer .
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.
WHAT IS OUTPUT?
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.
4 COMMON TYPES
Consists of characters that are used to create words, sentences, and paragraphs.
A character is a letter, number, punctuation mark, or any other symbol that requires one byte of computer storage space.
Are digital representations of non-text information such as drawings, charts, and photographs. Graphics also can be animated, giving them the illusion of motion.
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 output device is any computer component capable of conveying information to a user.
Commonly used output devices include display devices, speakers, headset, data projector, facsimile machines and multifunction devices .
A data projector takes the image that displays on a computer screen and projector it into a screen so that an audience of people can see the image clearly.
Data projectors can be large devices attached to ceiling or wall in an auditorium, or they can be small portable devices. Two types of smaller, lower-cost units are LCD projectors and DLP projectors .
LIQUID CRYSTAL DISPLAY
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.
DIGITAL LIGHT PROCESSING (DLP)
A digital light processing (DLP) projectors uses tiny mirrors to reflect light, producing crisp, bright, colorful images that remain in focus and can be seen clearly even in a well-lit room.
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.
CRT MONITORS (cont.)
Monitor that display only one color are considered monochrome. A monochrome monitor display text, graphics and video information in one color (usually white, amber or green ) on a black background.
Like a television set, the core of a CRT monitor is a large glass tube called a cathode ray tube (CRT).
The computer monitor, screen or VDU (visual Display Unit ) is the most common output devices.
Screen sizes are measured diagonally and are still quoted in inches. Larger monitor make working at a computer easier on the eyes and are essential for use in DTP (Desktop Publishing) and CAD work.
Relatively cheap and reliable, can display text and graphics in a wide range of colors. They are also quiet and do not waste paper.
No permanent copy to keep and unsuitable for users with visual problems .
GAS PLASMA MONITORS
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.
High-definition television (HDTV) is a type of television set that works with digital broadcasting signals and support a wider screen and higher resolution display than a standard television set.
When you use a standard television set as a monitor for your computer, the output must be converted to an analog signal that can be displayed by the television set.
Printers are primary output devices used to generate information from the computers. These output are often referred to as “Hard Copies” or “Printout” in computer jargon.
Character printers are the slowest printers since they print character by character. There are two types of character printers:
DOT-MATRIX PRINTER INK JET PRINTER LASER PRINTER
TYPES OF PRINTERS
Limited to situations where carbon copies are needed and the quality is not too important.
Typical uses might be in warehouse where duplicate copies of orders need to produce quickly and cheaply.
The printing quality is low because of this impact these printers can be quite noise.
The purchase cost is low and the running costs are very low.
Can print fairly quickly, if you remember that multiple copies are being printed in one print run.
Robust and can operate in harsh environments.
If several sheets of self-carbonating paper are placed into the printer then the impact will produce multiple copies.
TYPES OF PRINTERS (cont.)
A popular choice for home and school use where small amounts of printing are done
The ink cartridges can be expensive so running costs can be high.
Speed is slow compared to a laser printer.
Relatively inexpensive and produce high quality black and white or color printing.
TYPES OF PRINTERS (cont.)
Common wherever fast, high quality printing is required.
Non color laser printers are more expensive than ink-jet printers (but the difference is narrowing).
Color laser printers are ‘considerably more expensive’ (but their speed and high quality output means they are becoming more popular).
Quiet and fast and produce high quality printouts.
Running cost are low because although toner cartridges are expensive to replace, they last a long time.
A system's speaker is the component that takes the electronic signal stored on things like CDS, Tapes, and DVDs and turns it back into actual sound that we can hear.
A device that draws pictures on paper based on commands from computer.
Plotter differs from printer in that they draw lines using a pen. Multicolor plotter use different colored pens to draw different colors.
FACSIMILE (FAX) MACHINE
A facsimile (fax) machine is a device that transmits and receives documents over telephone lines. The documents can contain text, drawings, or photographs, or can be handwritten.
When sent or received via a fax machine, these documents are known as faxes .
WHAT IS STORAGE?
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).
WHAT IS STORAGE? (cont.)
Storage devices can function as sources of input and output.
For example, each time a storage devices transfer data, instruction, and information from a storage medium into memory-a process called reading-it function as an input source.
When a storage device transfer these item from memory to a storage medium-a process called writing- it function as an output source.
WHAT IS STORAGE? (cont.)
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.
CHARACTERISTICS OF A FLOPPY DISK
To protect them from accidentally being erased, floppy disk have a write-protect notch.
A write-protect notch is a small opening in the corner of the floppy disk with a tab that you slide to cover or expose the notch.
CHARACTERISTICS OF A FLOPPY DISK (cont.)
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.
FLOPPY DISK DRIVE
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.
FLOPPY DISK DRIVE (cont.)
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.