History Of Computers PDF

CHAPTER 1 HISTORY OF COMPUTERS What is a computer? Most if not all people today can probably tell you what a computer is. But how does one define what a computer? A computer is a machine that manipulates data according to a set of instructions. GENERATIONS OF COMPUTER First Ge...

CHAPTER 1 HISTORY OF COMPUTERS What is a computer? Most if not all people today can probably tell you what a computer is. But how does one define what a computer? A computer is a machine that manipulates data according to a set of instructions. GENERATIONS OF COMPUTER First Generation (1940-1956) – Vacuum Tubes The first computers used vacuum tubes for circuitry and magnetic drums for memory, and were often enormous, taking up entire rooms. They were very expensive to operate and in addition to using a great deal of electricity, generated a lot of heat, which was often the cause of malfunctions. First generation computers relied on machine language, the lowest-level programming language understood by computers, to perform operations, and they could only solve one problem at a time. Input was based on punched cards and paper tape, and output was displayed on printouts. The UNIVAC and ENIAC computers are examples of first-generation computing devices. The UNIVAC was the first commercial computer delivered to a business client, the U.S. Census Bureau in 1951. A UNIVAC computer at the Census Bureau. Image Source: United States Census Bureau. Second Generation (1956-1963) - Transistors Transistors replaced vacuum tubes and ushered in the second generation of computers. The transistor was invented in 1947 but did not see widespread use in computers until the late 1950s. The transistors are far superior to the vacuum tubes, allowing computers to become smaller, faster, cheaper, more energy-efficient and more reliable than their first-generation predecessors. Though the transistors still generated a great deal of heat that subjected the computers to damage, it was a vast improvement over the vacuum tube. Second-generation computers still relied on punched cards for input and printouts for output. Second-generation computers moved from cryptic binary machine language to symbolic, or assembly, languages, which allowed programmers to specify instructions in words. High-level programming languages were also being developed at this time, such as early versions of COBOL and FORTRAN. These were also the first computers that stored their instructions in their memories, which moved from a magnetic drum to magnetic core technology. The first computers of this generation were developed for the atomic 1.energy IC (integrated industry. circuits) – 3rd generation 1 Third Generation (1964-1971) - Integrated Circuits The development of the integrated circuit was the hallmark of the third generation of computers. Transistors were miniaturized and placed on silicon chips, called semiconductors, which drastically increased the speed and efficiency of computers. Instead of punched cards and printouts, users interacted with third generation computers through keyboards and monitors and interfaced with an Operating System (O.S), which allowed the device to run many different applications at one time with a central program that monitored the memory. Computers for the first time became accessible to a mass audience because they were smaller and cheaper than their predecessors. Fourth Generation (1971-2010) - Microprocessors The microprocessor brought the fourth generation of computers, as thousands of integrated circuits were built onto a single silicon chip. What in the first generation filled an entire room could now fit in the palm of the hand. The Intel 4004 chips, developed in 1971, located all the components of the computer— from the central processing unit and memory to input/output controls—on a single chip. In 1981 IBM introduced its first computer for the home users, and in 1984 Apple introduced the Macintosh. Microprocessors also moved out of the realm of desktop computers and into many areas of life as more and more everyday products began to use microprocessors. As these small computers became more powerful, they could be linked together to form networks, which eventually led to the development of the Internet. Fourth generation computers also saw the development of GUIs, the mouse and other hand- held devices. 2 Fifth generation (present and beyond) – Artificial Intelligence Fifth generation computing devices, based on artificial intelligence, and are still in development, though there are some applications, such as voice recognition, that are being used today. The use of parallel processing and super-conductors is helping to make artificial intelligence a reality. Quantum computation and molecular and nano- technology will radically change the face of computers in years to come. The goal of fifth-generation computing is to develop devices that respond to natural language input and are capable of learning and self- organization. CLASSES OF COMPUTERS Computers can be classified by their size and power as follows: Micro Computers Are the most common type of computers in existence today, it was introduced with the advent of single chip large scale integrated circuit computer processors 3 Minicomputers or Midrange Computers The term "Mini computer" was coined at the time when most computers were cabinet sized Mini computers were much smaller, less powerful, and much less expensive The first Mini computers generally only performed one task at a time, while bigger computers ran multi-tasking operating systems, and served multiple users Mainframe Computers Also known as “big iron” which refers to large, expensive, ultra-fast computers. Are computers used mainly by large organizations for critical applications, typically bulk data processing such as census, industry and consumer statistics, ERP (Enterprise Resource Planning ), and financial transaction processing. A very large and expensive computer capable of supporting hundreds, or even thousands, of users simultaneously. 4 Servers Usually refer to a computer that is dedicated to the task of storing and retrieving large amounts of data. For example, a large computer dedicated to a database may be called a "database server". "File servers" manage a large collection of computer files. "Web servers" process web pages and web applications. Smaller servers are actually personal computers that have been dedicated to the task of storing data for other personal computers Workstation A powerful, single-user computer. A workstation is like a personal computer, but it has a more powerful microprocessors and higher- quality monitor. 5 Supercomputer An extremely fast computer that can perform hundreds of millions of instructions per second. A supercomputer is focused on performing one task involving intense numerical calculations such as weather forecasting and solving scientific problems. - CHARACTERISTICS OF COMPUTERS All computers have certain common characteristics irrespective of their type and size. Computers are not just adding machines; they are capable of doing complex activities and operations. Computers are what they are because of the following characteristics. Word Length - a digital computer operates on binary digits – 0 and 1. It can understand information only in terms of 0s and 1s. A binary digit is called a bit. A group of 8 bits is called a byte. The number of bits that a computer can process at a time in parallel is called its word length. 6 Speed - computers can calculate at very high speeds. A microcomputer, for example, can execute millions of instructions per second over and over again without any mistake. As the power of the computer increases, the speed also increases. For example, supercomputers can operate at speeds measured in nanoseconds and even in picoseconds – one thousand to one million times faster than microcomputers. Storage - computers have their main memory and auxiliary memory systems. A computer can store a large amount of data. The factor that makes computer storage unique is not that it can store vast amount of data, but the fact that it can retrieve the information that the user wants in a few seconds. Accuracy - The accuracy of a computer system is very high. Errors in hardware can occur, but error detecting and correcting techniques will prevent false results. In most cases, the errors are due to human factor rather than the technological flaws. Versatility - Computers are very versatile machines. They can perform activities ranging from simple calculations to performing complex CAD modeling and simulation to navigating missiles and satellites. Computers can communicate with other computers and can receive and send data in various forms like text, sound, video, graphics, etc. Automation - the level of automation achieved in a computer is phenomenal. It is not a simple calculator where you have to punch in the numbers and press the ―equal to‖ sign to get the result. Once a task is initiated, computers can proceed on its own till its completion. Diligence - diligence means being constant and earnest in effort and application. Human beings suffer from weakness like tiredness, lack of concentration, etc. Humans have feelings, they become sad, depressed, bored, and negligent and it will reflect on the work they do. WHAT COMPUTERS CAN DO In business, computers have become very crucial that we can‘t even think how we will be able to survive without them. Business use computers for a variety of purposes ranging from decision-making to electronic commerce. 7  In medicine today, computers are used for everything from diagnosing illnesses to monitoring patients during surgery and controlling permanent prostheses. Now, computers have found their way to classrooms and everyone from school children to research students use computers to work for their own intellectual benefit. Today, the military uses computers in a variety of ways – aboard ships, submarines and fighter planes as well as in certain weapons and satellites. Musicians and singers have teamed up with computers to create an amazing range of instruments and sounds simply by playing a keyboard. The Musical Instrument Digital Interface (MIDI) is a system that synchronizes hardware and software. Computers have found their way into the household. Most of the household appliances and gadgets have computers in them. The computer which fine tunes the images in your television, which automates your washing machine and microwave oven examples of the computer revolutions that is happening. WHAT COMPUTERS CAN’T DO There is no doubt that computers are fulfilling their promise to perform certain tasks better, faster and cheaper. Along with fears about computers, there have long been great expectations about how computers would revolutionize our world. But some of the benefits people expected from computers way back in 1950s just haven‘t happened. Productivity - Computers haven‘t yet met all our expectations as a productivity improvement tool. Sometimes it takes longer to do things with a computer than it would to do them manually. Sometimes it takes too much time to learn how to use an application program that is supposed to increase productivity. Reasoning - In 1949 a book entitled Cybernetics by Norbert Weiner (Cambridge: MA, MIT Press, 1949) stated that the computer shared similarities with the brain and the human nervous system. Thus, it seems fair to say that in the same way we have built machines to replace human labour, we have also sought to build machines that do certain kind of thinking for us. But computers still lack many of the mental capabilities possessed by five-year-old children. Simply put, computers can‘t think. Errors - computers don‘t make errors, people do – either in the way they program computers or in they way they use them. However, computers are extremely finicky machines and often frustratingly literal. The computer does not allow spelling mistakes or typos. Many of the problems with computers occur because the computer can‘t tell the difference between doing something sensible versus something ridiculous. 8 The Parts of Computer System Hardware - is any part of the computer you can touch. It 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). Users - 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. Data - consists of individual facts or bits of information, which by themselves may not make much sense to a person. The computer reads and stores data of all kinds – whether words, numbers, images or sounds – in the form of numbers. Consequently, computerized data is digital, meaning that it has been reduced to digits, or numbers. Computer Terminologies Application Software - Software that is designed and written for a specific personal, organizational, or processing task, such as graphics software. Alt - The Alt key doesn‘t do anything by itself, But if you hold it down while pressing another key, the effect of that key may be different from usual. Exactly what will happen will depend on what program is running at the time. Arrow keys - A set of 4 keys at the right of the computer keyboard that can be used to control the movement of the cursor on the screen up, down, left and right. Caps Lock - A key that toggles the keyboard between upper-case and lower-case modes. When caps lock is off, striking a key will produce a lower case letter, and holding down the ‗shift‘ key while striking a key will produce a capital letter 9 CD-ROM - Compact Disc Read-Only Memory. Optical storage medium that uses the same technology as audio CD formats. CD-ROMs can hold hundreds of megabytes of data, but a CD-ROM drive can typically only read data from a CD. A writeable CD-ROM is needed to save or modify files on a CD-ROM. CLICK - To depress and release a mouse button quickly. (In windows, the term ―click‖ usually refers to the left mouse button. Clip Art - A collection of images you can use in various documents. Clip art is often distributed on CD-ROM in large collection (thousands of clip art pieces) organized into categories, or available on the World Wide Web. Control Panel - A program that comes with Windows that enables you to make settings for many Windows actions, such as changing network, keyboard, printer, and regional settings. Some programs (including many video card drivers) may add sections to the control panel for you to use to configure that program. Copy - A command on the Edit menu that adds data (text or pictures) to the clipboard, while leaving the original data unchanged. Used often with the ―paste‖ command. CPU - CPU stands for Central Processing Unit and is often, simply called, the processor. The CPU is a microchip that is installed on a motherboard and acts as the computer‘s brain-performing calculations and coordinating the hardware components. Ctrl - A special key on most computer keyboards that, when used in combination with other key, allows the user to easily access special controls. For example, Ctrl+S save a file in most Windows programs. Ctrl+Alt+Del - A common PC hotkey combination. Pressing the Ctrl, Alt, and Del keys simultaneously in a DOS environment would automatically restart (warm boot) the computer. The combination brings up the ―close program‖ dialog box which allows users the choice of shutting down a specific program or restarting the computer. Cursor - A blinking character that indicates the location of the next input on the display screen. The cursor indicates where you are working in a document or program. 10 Cut - A command on the Edit menu that adds data (text or pictures) to the clipboard by removing it from its original document or position in that document. Default - Settings or options the computer automatically adopts if the user does not specify any. Delete - A key on the keyboard that erases information on the screen. Desktop - The main workspace in a graphical user interface such as Windows or Macintosh Systems. Users open and work with files and programs on the desktop, and can store files and shortcuts there as well. The user can also customize the look of the desktop with images or wallpaper and custom icons. Disk - Refers to the most common form of data storage that uses disks of magnetized materials to save data. Diskette - The actual term for a floppy disk Document - A file created using an application. For example, you might create a text document using a word processing application (such as Word) or a picture document using a graphic application Double-click - To depress and release a mouse button twice in quick succession. (In Windows, ―double-click‖ usually refers to the left mouse button) Download - To copy or move a file from another computer or disk onto another. Drag - To move an object on the screen from one place to another by clicking it with the mouse, holding the mouse button down, and pulling it to where you want it to be. Drag and Drop - Describes a particular action you can make with the mouse. Click an object, such as a folder, then hold down the mouse button as you drag the object to a new location. You drop the object by releasing the mouse button. Drag and drop can be used to easily move, print, delete. 11 Driver - A set of software that contains instructions that allows the computer to communicate with its peripheral devices. Enter - A key on the keyboard that, when pressed, instructs the computer to do something with the data just typed in. Esc - Used to exit or stop a program immediately, or to cancel what is being done at the moment and return to a previous screen File - A computer file is similar to a paper document holding related information. For example, each computer program or document is stored in a separate file, designated by its own filename File Extension - The final part of a filename that denotes the file format. The extension is usually three to four letters set apart from the rest of the file name by a period. Filename - A name specified by either the user, programmer, or software, comprised of alphanumeric characters, to identify a file and its contents. Different programs and operating systems have their own naming rules Folder - A collection of files. Folders can hold files and other folders for organizational purposes. Font - A description of how to display a set / size of characters. Function keys - A set of programmable keys on a keyboard (typically across the top of the keyboard) labelled F1 through F12, that perform different tasks, determined by the various software programs Gigabyte or GB - A unit of data measurement equal to approximately one billion bytes. GUI (Graphical User Interface) - The name given to an operating system or operating environment that uses pictural representations (icons) and menus, with a pointing device concept to execute commands and other tasks, rather than requiring the user to type commands 12 Hard Copy - Refers to a document printed on paper, rather than saved in ―soft‖ form on a disk or displayed on a screen. Hard disks - Commonly refers to a form of magnetic media that uses a hard metal disk to store data. Help - A program that gives you information about how to run Windows and its programs, including how to use Help program. Are also available in most currently released programs Home - Is a navigation key for the cursor. It will move the cursor to the beginning of the current line Icon - A pictorial representation of a program or software function or feature. Insert - Is a toggle key. That is, repeatedly pressing it will alternate between two effects Install - Loading and copying a program‘s files to a computer‘s disk drive and configuring it to run Keyboard - An input device based on the standard QWERTY typewriter configuration. Computer keyboards typically have more keys and features than typewrites, but work in much the same way Menu - A list of operations or tasks available to a user in a given program, usually organized in some logical fashion. Users access a function or command by selecting it from the menu. Monitor - A screen which allows the user to watch and interact with the computer. My Computer - An icon present on the Windows desktop that enables users to view drives, folders, and files. 13 Num Lock - A key on the keyboard that toggles the Number Pad between arrow keys and number keys. Paste - A command on the Edit menu that inserts data copied to the clipboard into a document Page down - The page down key is navigation key which will drop the displayed area down the page one screens worth. It doesn‘t necessarily move a whole literal page at a time. That would depend on the height of a page. Page Up - The page up key is navigation key which will move the cursor up the displayed area one screen‘s worth. It does not usually move a literal page at the time. That would depend on the height of a page. Print screen - Under Windows pressing the Print Screen key sends a copy of the screen to the Clipboard. You must then paste to an appropriate program and print from there. Recycle Bin - A special folder in Windows where deleted files are sent when the user gives the command to delete them. They reside in the recycle bin until the user gives the command to permanently erase them (‗Empty Recyle Bin) giving the user the chance to recover any information accidentally deleted Restore - To return data on a disk to its previous state, typically by using a backup copy of the files. You can restore files that have been damaged or corrupted backup to the state they were in when you backed them up. Right click - (on a mouse that has more than one button) to quickly depress and release the right mouse button Scanner - An optical input device that creates a photographic copy of text, drawings, and images for storage and manipulation by graphic and word processor programs in the computer 14 Screen Saver - A varying pattern or graphic that appears on the screen when the mouse and keyboard have been idle for a user-definable period of time. Originally used to prevent a static background from being ―burned into‖ the screen phosphorus, this is rarely a problem with modern monitors. Scroll Bar - Allow you to select a value within a range, such as what part of a document to see. Select - To specify a section of text or graphics for initiating an action. Shortcut - Another name for Hotkey Combination (also called a keyboard shortcut). In Windows, a file used to ―point‖ to a file or object in another location. When you open the shortcut, you are, in effect, opening the file the shortcut points to the target. Shift - Used in combination with the alphabetic keys to get upper case. With a numeric/symbol key using the Shift key will give the character at the top of the key. The Shift key can be used in combination with the Alt and Control keys to change the effects of another key. Spacebar - Is used to enter blank spaces in text. Sometimes it can also be used instead of a mouse click on buttons. Tab - Used to moved the cursor over to the right to a pre-set point. This is especially used in word processing to line up text vertically. Text Box - A space in the dialog box where text or numbers can be entered so that a command can be carried out. Text File - A file containing only text characters Thumbnail - A miniature rendition of a graphic file. A thumbnail gives an idea of what the full-size graphic looks like, and is usually used as a gateway to view the full- size graphic. 15 Title Bar - The bar at the top of a program or document window that shows you what its title is. The control menu, maximize, minimizes, restore, and task bar buttons can be accessed in the title bar. Tool Bar - A collection of buttons that typically make the more common tools for an application easily accessible. Although often grouped in a line under the menus, a toolbar can be located on the left or right side of the working area. Update - To install the latest version of a program, or to record the latest version of a program, or to record the latest information in a file or other document. Upload - To copy or move a file from one computer or drive to another computer or drive. It also means to transfer a file from your computer by attaching it to an email or moving it to a web based upload area. URL - Uniform Resource Locator, a string of text used to identify and locate a file on a computer network, like the internet. URL looks like this http//www.google.com User - A person who operates and uses a computer User-friendly - Programs that have been thoughtfully designed to be intuitive and self- explanatory to the average user, with a minimal chance of mistakes. Virus - A computer virus is a program written and then hidden in another program, ―program x‖. When ―program x‖ is executed (run) the virus program is unleashed and is able to do it‘s damage. The damage can range from a ―friendly‖ joke‖ to a complete destruction of other programs and data. Wallpaper - A graphic used to cover the ―desktop‖ or background of a graphical user interface such as Windows and Firefox. The wallpaper usually serves no purpose other than to improve the appearance of your workspace. 16 FLOWCHARTING Introduction, Basic Symbols and Variables Flowchart - use of symbols and phrases to designate the logic of how a problem is solved (SCHN95) - a common method for defining the logical steps of flow within a program by using a series of symbols to identify the basic Input, Process and Output (IPO‘s) function within a program (TRAI96) - a diagram representing the logical sequence in which a combination of steps or operations is to performed. It is a blueprint of the program (LAPU86). The basic symbols used in programming are presented in Table 1. Table1. Basic Flowchart Symbols SYMBOL NAME DESCRIPTION TERMINAL Defines the starting and ending point INITIALIZATION The preparation or initialization of memory space for data processing INPUT/OUTPUT The inputting of data for processing and the printing out of processed data PROCESS Manipulation of data (assignments and mathematical computation) DECISION Two alternative execution paths are possible. The path to be followed is selected during the execution by testing whether or not the condition specified within the outline is fulfilled. FLOWLINES Defines the logical sequence of the program. It points to the next symbol to be performed ON-PAGE CONNECTOR Connects to the flowchart to 1 avoid spaghetti connection on the same page. 17 SYMBOL NAME DESCRIPTION OFF-PAGE CONNECTOR Connects the flowchart on A different page to avoid spaghetti connection. DECISION Process conditions using relational operators. Used for trapping and filtering data Variables - The next most important thing to know is how data are presented in the program. Recall that data are entered into the program using a keyboard or mouse, and the data entered for processing are saved on a certain location. This location is called variable. Variable is a primary storage location that can assume different numeric or alphanumeric values. It is also a memory space allocated by a computer user for processing and storing data. Data type - Is the type of the data being processed in the program. However, data type is language specific and may have different representations. Table 2. Basic Data Types DATA TYPE DESCRIPTION EXAMPLE Integer whole number 10 355 1590 54765 1 34000 Float or double integer with decimal 3.1416 0.12 1.01 12.12 numbers 99.99 0.04 Character alphabets and special J W A * & ? characters String Combination of characters sum age int_1 a_total grand_total Boolean Reply of the compiler in the Values are either 1 for YES program that is performed or ) for NO behind the scene. Note: * used mostly by all programming languages ** C/C++, Java, Visual Basic and other programming languages specific 18 *** Note that the data types above are not the only data types used in programming. Other programming language may have their own set of data types with specific descriptions that are not presented above. Table 3. Sample variable names using Hungarian Notation VARIABLE NAME DATA TYPE DESCRIPTION IntSum Integer Sum DblTax Double Tax FltRate Float Rate ChrReply Character Reply StrLname String Lname BooAns Boolean Ans Data type is important in programming. However, data type is unique to every programming language. In the study of programming logic, data types will not be integrated in the discussion to allow pure analysis and logic development among students. The standard naming convention for variable used without any biases to any programming language are presented through its characteristics. Variables name characteristics  Must be descriptive and significant to the data, problem and its solution. It should be descriptive enough to identify the process or data it is referring to.  Combination of alphanumeric characters(alphabet, numbers and special characters) can be used as a variable name provided that it starts with an alphabet.  Although the length of variable name can have 256 characters, the lesser the number of characters the more efficient the program is. Examples: class_size tuition int1 income sum char3 f_name answer net_income l_name total grand_total Computer Operators: Processing Data The languages of computers need to be converted to a language that a CPU can understand. For the programmer to instruct 19 Table 4 Arithmetic Operators OPERATION SYMBOL EXAMPLE EXPLANATION Multiplication * A*B Multiply the value of variable A to the value of variable B Division / X/Y Divide the value of variable X by the value of variable Y Addition + Int1 + int2 Add the value of variable int1 to the value of Subtraction - A-B Subtract the value of variable B from the value of variable A Exponentiation ^ C^2 Square the value of variable C https://yonnysite.wordpress.com/2015/07/25/the-fivegeneration-of-computer-1st-5th/ 20