Saturday, 25 August 2018
Data representation, and Data processing in a computer:
Definition of Data:
• Data is distinct pieces of information, usually formatted in a special way. All software is divided into two
• general categories: data and programs. Programs are collections of instructions for manipulating data.
• Data can exist in a variety of forms -- as numbers or text on pieces of paper, as bits and bytes stored in electronic memory, or as facts stored in a person's mind.
• Strictly speaking, data is the plural of datum, a single piece of information.
• In practice, however, people use data as both the singular and plural form of the word.
Basic data type
• In programming, classification of a particular type of information. It is easy for humans to distinguish between different types of data.
• We can usually tell at a glance whether a number is a percentage, a time, or an amount of money. We do this through special symbols -- %, :, and $ -- that indicate the data's type.
• Similarly, a computer uses special internal codes to keep track of the different types of data it processes.
Most programming languages require the programmer to declare the data type of every data object, and most database systems require the user to specify the type of each data field. The available data types vary from one programming language to another, and from one database application to another, but the following usually exist in one form or another:
• integer : In more common parlance, whole number; a number that has no fractional part.
• floating-point : A number with a decimal point.
• For example, 3 is an integer, but 3.5 is a floating-point number.
character (text ): Readable text
character (text ): Readable text
Storage of data as files
• Computer data storage, often called storage or memory, is a technology consisting of computer components and recording media used to retain digital data.
• It is a core function and fundamental component of computers.
• The central processing unit (CPU) of a computer is what manipulates data
by performing computations.
by performing computations.
• A modern digital computer represents data using the binary numeral system.
• Text, numbers, pictures, audio, and nearly any other form of information can be converted into a string of bits, or binary digits, each of which has a value of 1 or 0.
• The most common unit of storage is the byte, equal to 8 bits.
How Computer process data:
• The CPU, or Central Processing Unit, is the part of the computer where work gets done. In most computers, there is one processing chip
• ALU stands for Arithmetic/Logic Unit
• This is the part that executes the computer's commands.
A command must be either a basic arithmetic operation:
+ - * /
or one of the logical comparisons: >< =not=
A command must be either a basic arithmetic operation:
+ - * /
or one of the logical comparisons: >< =not=
• Everything has to be broken down into these few operations.
• The ALU can only do one thing at a time but can work very fast.
• Main Memory stores the commands that the CPU executes and the results.
• This is where the computer stores the data and commands that are currently being used.
• When the computer is turned off, all data in Main Memory vanishes.
• A data storage method of this type is called volatile since the data "evaporates."
• The CPU can fetch one piece of data in one machine cycle.
• This is the part of the computer that controls the Machine Cycle.
• It takes numerous cycles to do even a simple addition of two numbers.
• Fetch -
• get an instruction from Main Memory
• Decode -
• translate it into computer commands
• Execute -
• actually process the command
• Store -
• write the result to Main Memory
• This is the instructions that the computer uses to tell itself how it "operates". It's the answer to "Who am I and what can I do?"
• Some common operating systems are DOS, various versions of Windows, OS/2, UNIX, LINUX, System 7. These all behave in very different ways and have different hardware requirements. So they won't all run on all machines
• These are the various programs that are currently running on the computer.
• By taking turns with the Machine Cycle, modern computers can have several different programs running at once. This is called multi-tasking.
• Each open application has to have some data stored in Main Memory, even if the application is on rest break and is just sitting there.
Input / Output Storage
• When you enter new data, the keystrokes must be stored until the computer can do something with the new data.
• When you want data printed out or displayed, it must be stored somewhere handy first.
• The numbers and characters that are the intermediate results of computer operations must be stored until the final values are calculated. These values "in progress" are kept in temporary locations.
• For example, if the computer is adding up the numbers 3, 5, and 6, it would first add 3 to 5 which yields a value of 8. The 8 is stored in working storage. Then the 8 and 6 are added and the new value 14 is stored. The value of 14 is now available to be displayed on the screen or to be printed or to be used in another calculation.
• One hopes that there is always some storage space that is not in use.
• If space runs out in Main Memory, the computer will crash, that is, stop working.
Tuesday, 14 August 2018
Keyboard is the most common input device used for entering text data directly into a computer. A computer keyboard is similar to that of a typewriter, but it has additional keys as well. The most commonly available computer keyboard has 104 keys. Data is entered into a computer by pressing a set of keys available with the keyboard. Keyboard is the oldest input device, which is still being used with the modern computer. When user presses a key, the corresponding character appears on screen.
1. Keyboard Keys:
The keys of the keyboard are divided as:
1. Numeric keys
2. Character/Alphanumeric keys
3. Punctuation keys
4. Functional keys
5. Special purpose keys
6. Cursor movement keys
a. Numerical keys:
Numeric keyboard is usually located on right side of the keyboard with its 10 digits (0 to 9) and mathematical operators (+,-,*,/). These keys are used to input numeric information.
b. Character/Alphanumeric keys:
These keys are mainly used to enter characters. These keys include keys for characters like a-z, A-Z, 0-9, enter key and shift key.
c. Punctuation keys:
To type the special punctuation characters, punctuation keys, such as the colon (:), the semicolon (;), the question mark (?), single quotes (‘), and double quotes (“) are used.
d. Function keys:
These keys are arranged at the topmost row of the keyboard and each one of them has a special function key differs from software to software. Normally, a standard keyboard has 12 function keys (F1, F2 …F12).
e. Special purpose keys:
These keys are used to perform special functions like deletions or moving a page up or down. Some others keys in this category are Home, End, Insert, Ctrl and Alt etc.,
f. Cursor movement keys:
These keys allow us to move around the screen. Most keyboards have the keys such as arrow keys to move the cursor up/down.
2. Multimedia keyboard:
A multimedia keyboard is designed to make it one touch simple for the user to access often used programs. Multimedia keyboard contains various additional keys to perform functions like volume control, launching internet explorer, changing song and video tracks, launching e-mail software etc., A typical multimedia keyboard contains buttons that control various computer processes, such as turning on the compute’s power, putting the CPU to sleep, and waking it up again.
The web browser keys on a multimedia keyboard should be familiar to most internet users. Back, forward, stop, and refresh buttons are usually present on such keyboard. A specific type of multimedia keyboard is called a gaming keyboard. It is used for high-tech video games, can be even more expensive.
3. Wireless keyboard:
Wireless keyboards are also available today, but a higher price than wired keyboard. These keyboards do not have any wire attached to them. Wireless keyboard interacts with the computer through Bluetooth or infrared technology. Wireless keyboards transfer typing data to the computer via infrared beams. A beam of information is sent from the keyboard, as you type, to a receiver, which is plugged into the computer. Wireless keyboard operates on battery power rather than using electricity from the user’s computer.
Advantage of using wireless keyboard rather than a regular keyboard is that it offers much more mobility. A wireless keyboard can be used on a lap, in a bed, or just used while on the go for laptop users. Disadvantages of using a wireless keyboard are that it has to be installed & configured before it can be used. Regular keyboards on the other hand, run on plug & play software & work immediately after they are plugged in.
•Input devices are those peripheral devices that
are used to supply input to the computer.
•An input device converts input into suitable
binary form that can be accepted by the
Typical input devices are listed below:
üTouch ScreenüOptical Mark Reader (OMR)
Tuesday, 7 August 2018
Application software tells the computer how to accomplish specific tasks, such as word processing or drawing, for the user. Thousands of applications are available for many purposes and for people of all ages. Some of the major categories of these applications include. Word processing software for creating text-based documents such as newsletters or brochures.
» Spreadsheets for creating numeric-based documents such as budgets or balance sheets.
Database management software for building and manipulating large sets of data, such as the names, addresses, and phone numbers in a telephone directory.
» Presentation programs for creating and presenting electronic slide shows.
» Graphics programs for designing illustrations or manipulating photographs, movies, or animation.
» Multimedia authoring applications for building digital movies that incorporate sound, video, animation, and interactive features.
» Entertainment and education software, many of which are interactive multimedia events.
» Web design tools and Web browsers, and other Internet applications such as newsreaders and e mail programs.
» Games, some of which arc for a single player and many of which can be played by several people over a network or the Internet.
System software is any program (hat controls the computer’s hardware or that can be used to maintain the computer in some way so that it runs more efficiently. There are three basic types of system software:
» An operating system tells the computer how to use its own components. Examples of operating systems include Windows, the Macintosh Operating System, and Linux. An operating system is essential for any computer; because it acts as an interpreter between the hardware, application programs, and the use when a program wants the hardware to do something, it communicates through the operating system. Similarly, when you want the hardware to do something (such as copying or printing a file), your request is handled by the operating system.
» A network operating system allows computers to communicate and share data across a network while controlling network operations and overseeing the network’s security.
» A utility is a program that makes the computer system easier to use or performs highly specialized functions. Utilities arc used to manage disks, troubleshoot hardware problems, and perform other tasks that the operating system itself may not be able to do.
A personal computer would be useless if you could not interact with it because the machine could not receive instructions or deliver the results of its work. Input devices accept data and instructions from the user or from another computer system (such as a computer on the Internet). Output devices return processed data to the user or to another computer system.
The most common input device is the keyboard, which accepts letters, numbers, and commands from the user. Another important type of input device is the mouse, which lets you select options from on-screen menus. You use a mouse by moving it across a flat surface and pressing its buttons. Figure IB .10 shows a personal computer with a keyboard, mouse, and microphone.
A variety of other input devices work with personal computers, too: The trackball and touchpad are variations of the mouse and enable you to draw or point on the screen.The joystick is a swiveling lever mounted on a stationary base that is well suited for playing video games.
A scanner can copy a printed page of text or a graphic into the computer's memory, freeing you from creating the data from scratch.
A digital camera can record still images, which you can view and edit on the computer
» A microphone enables you to input your voice or music as data. The function of an output device is to present processed data to the user. The most common output devices are the monitor and the printer the computer sends output to the monitor (the display screen) when the user needs only to see the output. It sends output to the printer when the user requests a paper copy—also called a hard copy—of a document. Just as computers can accept sound as input, (hey can use stereo speakers or headphones as output devices to produce sound.
Printer; and speakers. Some types of hardware can act as both input and output devices. A touch
Screen, for example, is a type of monitor that displays text or icons you can touch.
When you touch the screen, special sensors detect the touch and the computer calculates the point on the screen where you placed your finger. Depending on the location of the touch, the computer determines what information to display or what action to take next.
Communications devices are the most common types of devices that can perform both input and output. These devices connect one computer 10 another—a process known as networking. The most common kinds of communications devices are modems, which enable computers to communicate through telephone lines or cable television systems, and network interface cards (NICs), which let users connect a group of computers to share data and devices.
In a computer, memory is one or more sets of chips that store data and/or program instructions, cither temporarily or permanently. Memory is a critical processing component in any computer Personal computers use several different types of memory, but the two most important arc called random access memory (RAM) and read-only memory (ROM). These two types of memory work in very different ways and perform distinct functions.
Random Access Memory
The most common type of memory is called random access memory (RAM). As a result, the term memory is typically used to mean RAM. RAM is like an electronic scratch pad inside the computer. RAM holds data and program instructions while the CPU works with them. When a program is laundered, it is loaded into and run from memory. As the program needs data, it is loaded into memory for fast access. As new data is entered into the computer, it is also stored in memory— but only temporarily. Data is both written to and read from this memory. (Because of this, RAM is also sometimes called read/write memory.) Like many computer components, RAM is made up of a set of chips mounted on a small circuit board (see Figure 1B.9). RAM is volatile, meaning that it loses its contents when the computer is shut off or if there is a power failure. Therefore, RAM needs a constant supply of power to hold its data. For this reason, you should save your data files to a storage device frequently, to avoid losing them in a power failure. (You will learn more about storage later in this chapter.)
RAM has a tremendous impact on the speed and power of a computer. Generally, the more RAM a computer has, the mote it can do and the faster it can perform certain tasks. The most common measurement unit for describing a computer’s memory is the byte—the amount of memory it takes to store a single character such as a letter of the alphabet or a numeral. When referring to a computer's memory, the numbers are often so large that it is helpful to use terms such as kilobyte (KB), megabyte (MB), gigabyte (GB), and terabyte (TB) to describe the values (see Table 1B.1). Today’s personal computers generally have at least 256 million bytes (256 MB) of random access memory. Many newer systems feature 512 MB or more.
Unlike RAM, Read-only memory (ROM) permanently stores its data, even when the computer is shut off. ROM is called nonvolatile memory because it never loses its contents. ROM holds instructions that the computer needs to operate. Whenever the computer's power is turned on, it checks ROM for directions that help it start up, and for information about its hardware devices.
The procedure that transforms raw data into useful information is called processing. To perform this transformation, the computer uses two components: the processor and memory.
The processor is like the brain of the computer; it organizes and carries out instructions that come from either the user or the software. In a personal computer the processor usually consists of one or more specialized chips, called microprocessors, which are slivers of silicon or other material etched with many tiny electronic circuits. To process data or complete an instruction from a user or a program the computer passes electricity through the circuits. The microprocessor is plugged into the computer’s motherboard. The mother-board is a rigid rectangular card containing the circuitry that connects the processor to the other hardware. The motherboard is an example o f a circuit the microprocessor board. In most personal computers, many internal devices such as video cards, sound cards, disk controllers, and other devices—are housed on their own smaller circuit boards, which attach to the motherboard.
In many newer computers, these devices are built directly into the motherboard. Some newer microprocessors are large and complex enough to require their own dedicated circuit boards, which plug into a special slot in the motherboard. You can think of the motherboard as the master circuit board in a computer.
A personal computer’s processor is usually a single chip or a set of chips contained on a circuit board. In some powerful computers, the processor consists of many chips and the circuit boards on which they are mounted. In either case, the term control processing unit (CPU) refers to a computer’s processor. People often refer to computer systems by the type of CPU they contain. A "Pentium 4” system, for example, uses a Pentium 4 microprocessor as its CPU.
Using all its parts together, a computer converts data into information by performing various actions on the data. For example, a computer might perform a mathematical operation on two numbers, then display the result. Or the computer might perform a logical operation such as comparing two numbers, then display that result. These operations are part of a process called the information processing cycle, which is a set of steps the computer follows to receive data, process the data according to instructions from a program, display the resulting information to the user, and store the results.
The information processing cycle has four parts, and each part involves one or more specific components of the computer:
» Input. During this part of the cycle, the computer accepts data from some source, such as the user or a program, for processing.
» Processing. During this part of the cycle, the computer’s processing components perform actions on the data, based on instructions from the user or a program.
» Output. Here, the computer may be required to display the results of its processing.
For example, the results may appear as text, numbers, or a graphic on the computer’s screen or as sounds from its speaker. The computer also can send output to a printer or transfer the output to another computer through a network or the Internet. Output is an optional step in the information processing cycle but may be ordered by the user or program.» Storage. In this step, the computer permanently stores the results of its processing on a disk, tape, or some other kind of storage medium. As with output, storage is optional and may not always be required by the user or program.
Computers come in many varieties, from the tiny computers built into household appliances, to the astounding supercomputers that have helped scientists map the human genome. But no matter how big it is or how it is used, every computer is part of a system. A complete computer system consists of four parts
The mechanical devices that make up the computer are called hardware. Hardware is any part of the computer you can touch. A computer’s hardware consists of interconnected electronic devices that you can use to control the computer’s operation, input, and output. (The generic term device refers to any piece of hardware.)
Software is a set of instructions that makes the computer perform tasks. In other words, software tells the computer what to do. (The term program refers to any piece of software.) Some programs exist primarily for the computer's use to help it perform tasks and manage its own resources. Other types of programs exist for the user, enabling him or her to perform tasks such as creating documents. Thousands of different software programs are available for use on personal computers.
Data consist of individual facts or pieces of information that by themselves may not make much sense to a person. A computer’s primary job is to process these tiny pieces of data in various ways, converting them into useful information. For example, if you saw the average highway mileages of six different cars, all the different pieces of data might not mean much to you. However; if someone created a chart from the data that visually compared and ranked the vehicles’ mileages, you could probably make sense of it at a glance. This is one example of data being processed into useful information.
People are the computer operators, also known as users. It can be argued that some computer systems are complete without a person’s involvement; however, no computer is totally autonomous. Even if a computer can do its job without a person sitting in front of it, people still design, build, program, and repair computer systems. This lack of autonomy is especially true of personal computer systems, which arc the focus of this book and are designed specifically for use by people.
Most people believe that computers must be extremely complicated devices, because they perform such amazing tasks. To an extent, this is true. As you will learn later in this book, the closer you look at a computer’s operation, the more complex the system becomes. But like any machine, a computer is a collection of parts, which are categorized according to the kinds of work they do. Although there are many, many variations on the parts themselves, there are only a few major categories. 1/ you learn about those families of computer components and their basic functions, you will have mastered some of the most important concepts in computing. As you will see, the concepts are simple and easy to understand. This lesson gives you a glimpse inside a standard desktop computer and introduces you to its most important parts. You will learn how these components work together and allow you to interact with the system. You also will discover the importance of software, without which a computer could do nothing. Finally, you will see that the user is (in most cases, at least) an essential part of a complete computer system.
People can list countless reasons for the importance of computers. For someone with a disability, for example, a computer may offer freedom to communicate, learn, or work without leaving home. For a sales professional, a PC may mean the ability to communicate whenever necessary, to track leads, and to manage an ever-changing schedule. For a researcher, a computer may be the workhorse that docs painstaking and time-consuming calculations. But if you took all the benefits that people derive from computers, mixed them together, and distilled them down into a single element, what would you have? The answer is simple: information. Computers are important because information is so essential to our lives. And information is more than the stuff you see and hear on television. Facts in a textbook or an encyclopedia are information, bur only one kind. Mathematical formulas and their results arc information, too, as arc the plans for a building or the recipe for a cake. Pictures, songs, addresses, games, menus, shopping lists, resumes— the list goes on and on. All these things and many others can be thought of as information, and they can all be stored and processed by computers. (Actually, if you work in one place and need to perform various tasks, a desktop computer is the best choice. Choose a desktop computer if you want to
» Work with Graphics-Intensive or Desktop Publishing Applications. Complex graphics and page-layout programs require a great deal of system resources, and a desktop system’s large monitor reduces eye fatigue.
» Design or Use Multimedia Products. Even though many portable computers have multimedia features, you can get the most for your money with a desktop system. Large screens make multimedia programs easier to see, and stereo-style speakers optimize sound quality.
» Set Up Complex Hardware Configurations. A desktop computer can support multiple peripherals—including printers, sound and video sources, and various external devices—at the same time. If you want to swap components, or perform other configuration tasks, a desktop system will provide many options.
Computers store these things as data, not as information, but you’ll learn the difference between the two later in the book.) So, when you consider the importance of computers in our society, think instead about the importance of information. As tools for working with information, and for creating new information, computers may be one of humanity's most important creations.
In many American homes, the family computer is nearly as important as the refrigerator or the washing machine. People cannot imagine living without it. In fact, a growing number of families have multiple PCs in their homes; in most cases, at least one of those computers has an Internet connection. Why do home users need their computers?
» Communications. Electronic mail (e-mail) continues to be the most popular use for home computers, because it allows family members to communicate with one another and to stay in contact with friends and coworkers.
» Business Work Done at Home. Thanks to computers and Internet connections, more people are working from home than ever before. It is possible for many users to connect to their employer’s network from home and do work that could not be done during regular business hours. Computers also are making it easier for people to start their own home-based businesses.
» Schoolwork. Today’s students are increasingly reliant on computers, and not just as a replacement for typewriters. The Internet is replacing printed books as a reference tool, and easy-to-use software makes it possible for even young users to create polished documents.
» Entertainment. If you had ever played a computer game, you know how enjoyable they can be. For this reason, the computer has replaced the television as the entertainment medium of choice for many people. As computer; audio, video, and broadcast technologies converge, the computer will someday be an essential component of any home entertainment center.
» Finances 'Computer’s and personal finance software can make balancing your checkbook an enjoyable experience. Well, almost. At any rate, they certainly make it easier, and home users rely on their PCs for bill paying, shopping, investing, and other financial chores.
More and more schools are adding computer technology to their curricula, not only teaching pure computer skills, but incorporating those skills into other classes. Students may be required to use a drawing program, for example, to draw a plan of the Alamo for a history class, or use spreadsheet software to analyze voter turnouts during the last century’s presidential elections. Educators see computer technology as an essential learning requirement for all students, starting as early as preschool. Even now, basic computing skills such as keyboarding are being taught in elementary school classes. In the near future, high school graduates will enter college not only with a general diploma, but with a certification that proves their skills in some area of computing, such as networking or programming.
Many of today’s successful small companies simply could not exist without computer technology. Each year, hundreds of thousands of individuals launch businesses based from their homes or in small-office locations. They rely on inexpensive computers and software not only to perform basic work functions, but to manage and grow their companies. These tools enable business owners to handle tasks—such as daily accounting chores, inventory management, marketing, payroll, and many others—that once required the hiring of outside specialists. As a result, small businesses become more self-sufficient and reduce their operating expenses.
Today, enterprises use different kinds of computers in many combinations. A corporate headquarters may have a standard PC-based network, for example, but its production facilities may use computer controlled robotics to manufacture products. Here are just a few ways computers are applied to industry:
» Design. Nearly any company that designs and makes products can use a computer-aided design or computer-aided manufacturing system in their creation.
» Shipping. Freight companies need computers to manage the thousands of ships, planes, trains, and trucks that are moving goods at any given moment. In addition to tracking vehicle locations and contents, computers can manage maintenance, driver schedules, invoices and billing, and many other activities.
» Process Control. Modem assembly lines can be massive, complex systems, and a breakdown at one point can cause chaos throughout a company. Sophisticated process-control systems can oversee output, check the speed at which a machine runs, manage conveyance systems, and look at parts inventories, with very little human interaction.
Not only are government’s big consumers of technology, but they help to develop it as well. “Presenting the Internet," the U.S. government played a key role in developing the Internet. Similarly, NASA has been involved in the development of computer technologies of all sorts. Today, computers play a crucial part in nearly every government agency:
» Population. The U.S. Census Bureau was one of the first organizations to use computer technology, recruiting mechanical computers known as “difference engines" to assist in tallying the American population in the early 20th century.
»Taxes. Can you imagine trying to calculate Americans’ tax bills without the help of computers? Neither could the Internal Revenue Service. In fact, the IRS now encourages taxpayers to file their tax returns online, via the Internet.
Military. Some of the world's most sophisticated computer technology has been developed primarily for use by the military. In fact, some of the earliest digital computers were created for such purposes as calculating the trajectory of missiles. Today, from payroll management to weapons control, the armed forces use the widest array of computer hardware and software imaginable.
Police. When it comes to stocking their crime-fighting arsenals, many police forces consider computers to be just as important as guns and ammunition. Today’s police cruisers are equipped with laptop computers and wireless Internet connections that enable officers to search for information on criminals, crime scenes, procedures, and other kinds of information.
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