Essential Computer Concepts

What Is a Computer?

A computer is defined as an electronic device that accepts information and instructions from a user, manipulates the information according to the instructions, displays the information in some way, and stores the information for retrieval later. Personal computers (PCs) are computers typically used by one person in a home or office, and is available as a desktop computer, a notebook computer, tablet PC, or subnotebooks. The following describes various types of computers:

One of the most common types of handheld computers is a smartphone, which is used to make and receive phone calls, maintain an address book, electronic appointment book, calculator, and notepad, send email, connect to the Internet, play music, take photos or video, and even perform some of the same functions as a PC.

A computer is different than a computer system. A computer system includes both computer hardware, or the physical components of the computer, and the software, or tangible programs, that run on the hardware. The design and construction of a computer is referred to as its architecture or configuration.


Data Representation

Data refers to the words, numbers, figures, sounds, and graphics that describe people, events, things, and ideas. Specifically, computers represent data as "on" with a 1 and "off" with a 0. These numbers are referred to as binary digits, or bits and a series of eight bits is called a byte. A kilobyte is 1024 bytes, a megabyte is 1,048,576 bytes, and a gigabyte is 1,073,741,824 bytes. It is common to say that a megabyte is about 1 million bytes and that a gigabtye is about 1 billion bytes. Personal computers commonly use the ASCII (American Standard Code for Information Interchange) system to represent character data.


Processing Hardware

A computer system's hardware and software works together to process data and commands. Modifying data is referred to as processing. Commands are instructions to the computer on how to process data.

In a computer, processing tasks occur on the motherboard, which is the main electronic component of the computer and is comprised of thousands of circuits on a circuit board. The most important piece of processing hardware on the motherboard is the microprocessor, also known as a processor or the central processing unit (CPU), which consists of transistors and electronic circuits on a silicon chip. In terms of processors, clock speed is measured in megahertz (MHz), millions of cycles per second, or in gigahertz (GHz), billions of cycles per second. A dual-core processor, which has two processors on a single chip, can process information up to twice as fast as a single-core processor, which has one processor on the chip. A quad-core processor, with four processors on a chip, processes information up to four times as fast as a single-core processor.

Cards are removable circuit boards that are inserted into slots on the motherboard to expand the capabilities of the motherboard, such as sound cards, video cards, modems, and others.


Memory and Storage

Computer memory is a set of storage locations on the motherboard. Memory is different from permanent storage, where the data you create and the instructions you use remain when you are not using them. Your computer has five types of memory: random access memory (RAM), cache memory, virtual memory, read-only memory (ROM), and complementary metal oxide semiconductor (CMOS) memory. RAM consists of electronic circuits on cards that plug into the motherboard, and it temporarily holds programs and data while the computer is on. Synchronous dynamic RAM (SDRAM) is used by most personal computers. CPU cache, or cache memory or RAM cache, is a special high-speed memory built into the microprocessor. Virtual memory is space on the computer's storage devices that simulates additional RAM. ROM is a set of electronic circuits on the motherboard that permanently stores the set of instructions that the computer uses to check the computer system's components to make sure they are working and activate the essential software that controls the processing function when you turn it on. CMOS memory is a chip installed on the motherboard that is activated during the boot process and identifies where essential software is stored. One of the easiest ways to make your computer run faster is to add more RAM.

All data and programs are stored as files. A computer file is a named collection of stored data. An executable file contains the instructions that tell a computer how to perform a specific task; for instance, the files that are used while the computer starts are the executable files. A data file is created by a user, usually with software. Magnetic storage media store data as magnetized particles on a surface. A hard disk, also called a hard disk drive, is the most common type of magnetic storage media. Optical storage devices are polycarbonate discs coated with a reflective metal on which data is stored using laser technology as a trail of tiny pits or dark spots in the surface of the disc. Optical storage devices include CD-ROMs and DVDs. CD-ROMs can store up to 700 MB and was the first standard optical storage device on personal computers. DVDs, though the same size as CD-ROMs, can store up to 15.9 GB of data and are the most popular medium for movies. New formats of optical storage include Blu-ray Discs, which are capable of storing up to 25 GB of data. Flash memory are small cards encased in plastic that are similar to ROM memory, except that they can be erased so that new data can be stored on them. Popular flash memory are USB flash storage devices, which are also called USB drives or flash drives. Flash memory is also used in digital cameras, handheld computers, video game controllers, and other devices. Special CD-ROMs, DVD-ROMs, and Blu-Ray discs can be written to by a computer that has either a CD writer, DVD writer, or Blu-Ray writer drive.


Input and Output

The data or instructions you type into the computer are called input. The result of the computer processing your input is referred to as output. The computer takes care of the processing function; you need additional components, called peripheral devices, to accomplish the input and output functions. In a typical personal computer, a user inputs data and commands by using an input device such as a keyboard or mouse. Many input devices have been designed ergonomically, meaning they have been designed to fit the natural placement of your hands and should reduce the risk of repetitive-motion injuries. There are many types of input devices such as:

People with physical impairments or disabilities can use computers because of advances in making computers accessible to everyone, called assistive technology through assistive devices.


Output devices show you the results of data processing, output. The most commonly used output devices are monitors and printers. There are variations on both including:

To display graphics, a computer must have a graphics card or video card, which is installed on the motherboard. Monitor screen size is the diagonal measurement from one corner of the screen to the other. Most monitors divide the screen into a matrix of small dots called pixels. Resolution is the number of pixels a monitor displays. Dot pitch (dp) measures the distance between pixels, so a smaller dot pitch means a sharper image.

A printer produces a paper copy of the text or graphics processed by the computer. The most popular printers for business use are laser printers. They use the same technology as a photocopier; a temporary laser image is transferred onto paper with a powdery substance called toner. The speed of laser printers is measured in pages per minute (ppm). A less expensive alternative to the laser printer is an inkjet printer, which sprays ink onto paper.


Data Communications

Data communications is defined as the transmission of data from one computer to another or to a peripheral device. The computer that originates the message is the sender. The message is sent over a channel; the computer that receives the message is the receiver, and the rules that establish an orderly data transfer are called protocols. The transmission protocol between a computer and its peripheral devices is handled by a device driver, or simply driver. An external peripheral device must have a corresponding port and cable that connects it to the computer. The data path between the microprocessor, RAM, and peripherals is the data bus. An external peripheral device must have a corresponding expansion port and cable that connect it to the computer. Inside the computer, each port connects to a controller card, sometimes called an expansion card or interface card. These cards plug into electrical connectors on the motherboard called expansion slots or slots. A USB port is a high-speed port that has become popular because of the wide range of devices that can be used by the port, including mice, keyboards, printers, and even external storage. Monitors are connected to computers through an HDMI, a DVI, or a VGA port. Speakers and a microphone connect to a computer via ports on the sound card. You can connect to another computer, a LAN, a modem (a device that connects your computer to a standard telephone jack or to a cable connection), or sometimes directly to the Internet using an Ethernet port.

A network connects one computer to other computers and peripheral devices, enabling you to share data and resources with others. Each computer that is part of the network must have a network interface card (NIC) installed. Network software establishes the communications protocols that will be observed on the network and controls the "traffic flow" as data travels throughout the network. A network with a server, which provides resources for users or other computers, and computers dependent on the server, called clients, is called a client/server network. Any device connected to the network is called a node. There are different types of networks such as:

Telecommunications means communicating over a comparatively long distance using a phone line or some other data conduit, typically with a modem. A modem is a modulator-demodulator and is used to connect your computer to a standard telephone jack. People who want to use a high-speed connection either over phone lines, such as a DSL (digital subscriber line), or over a cable connection, usually need to purchase an external DSL or cable modem separately. High-speed connections are often called broadband connections.

The Internet is the largest network in the world, connecting millions of people. Most people first experience the Internet by using electronic mail, more commonly called E-mail, which is sending a message from one user's computer to another user's computer where it is stored until the recipient opens it. Another benefit of using the Internet is the World Wide Web, often referred to simply as the Web. Information is stored on the Web as a special type of text file called a Web page. Web pages can include text, graphics, sound, animation, and video and a collection of Web pages is called a Web site. Hyperlinks, or links, are areas on a Web page that is programmed to connect to a particular file on the same network server, or even on a network server on the other side of the globe. Web browsing software, or a Web browser, is an application used on your computer to view Web sites.


Security Threats on Your Computer

Security refers to the steps a computer owner takes to prevent unauthorized use of or damage to the computer. There are several types of security threats that a computer and its user may face. Malware is a broad term that describes any program that is intended to cause harm or convey information to others without the owner's permission and include viruses and spyware. Viruses instruct your computer to perform destructive activities. Spyware programs track a computer user's Internet usage and send this data back to the company or person that created it. Antivirus software can be installed to help prevent and remove viruses. A firewall is like a locked door on a computer that prevents other computers on the Internet from accessing it. Some threats to users include phishing, which refers to the practice of sending e-mails to customers or potential customers of a legitimate Web site asking them to click a link in the e-mail that is not legitimate. The link leads to a spoofed site where the user is asked to verify or enter personal information. Another is pharming where a criminal breaks into a DNS server (a computer responsible for directing Internet traffic) and redirect any attempts to access a particular Web site to the criminal's spoofed site. A strong password is at least eight characters of upper and lowercase letters and numbers and should be used to protect data.


Computer Software

Software can be divided into two major categories: system software and application software. System software helps the computer carry out its basic operating tasks. Application software helps the user carry out a variety of specific tasks. System software is divided into operating systems, utilities, device drivers, and programming languages. An operating system controls basic input and output, allocates system resources, manages storage space, maintains security, and detects equipment failure. A system resource is any part of the computer system, including memory, storage devices, and the microprocessor, that can be used by a computer program. Microsoft Windows and Mac OS are referred to as operating environments because they provide a graphical user interface (GUI) that acts as a liaison between the user and the computer's hardware and software. Utilities are another category of system software that augments the operating system by taking over some of its responsibility for allocating hardware resources. Computer programming languages are used by programmers to write computer instructions.

Application software enables you to perform specific computer tasks, such as document production, electronic publisihng, web site creation, spreadsheet calculations, database management, graphics production, presentations, photo editing, multimedia authoring, accounting, and information management software. Document production software includes word processing software, desktop publishing software, E-mail editors, and Web authoring software. Web site creation and management software allows you to create and manage Web sites. Spreadsheet software is a numerical analysis tool with worksheets composed of a grid of columns and rows forming intersections called cells. You type numbers into the cells, and then create mathematical formulas in other cells that perform calculations using these numbers. Database management software lets you collect and manage data through fields and records. Graphics software allows you to create illustrations, diagrams, graphs, and charts. Presentation software allows you to display or project graphics and other information to a group, print them for quick reference, or transmit them to remote computers. Photo editing software allows you to manipulate digital photos. Multimedia authoring software allows you to record digital sound files, video files, and animations that can be included in presentations and other documents. Accounting software helps individuals and businesses create and track budgets. Information management software allows people to keep track of their schedules, appointments, contacts, and to-do lists.

Object linking and embedding (OLE) refers to the ability to use data from another file, called the source. Embedding is the copying and pasting of source data in a new file. Linking creates a connection between the source data and the copy in the new file, meaning the link updates the copy every time a change is made to the source data. The seamless embedding and linking of data in applications is commonly known as integration.


Computing in the Cloud

Cloud computing means that data, applications, and even resources are stored on servers accessed over the Internet rather than on users' computers, and you access only what you need when you need it. Some companies provide space and computing power to developers for a fee. Individuals might subscribe to a backup service such as Carbonite or Mozy so that their data is automatically backed up on a computer at the physical location of those companies. Google Docs and Microsoft Web Apps provide both free and paid versions of various applications that you access by logging in to their Web sites.