sign in sign up
<<
Home , Z3 (computer)

E-Content B.Ed ll Sem Paper Name: Education Paper code : BED 308(B) Unit : l

INTRODUCTION AND DEFINITION OF COMPUTER

A computer is a machine that can be instructed to carry out sequences of arithmetic or logical operations automatically via . are an electronic machine. "Computer" is gotten from the Latin "compute". This signifies, "A Machine that can make Calculation" signifies a machine that can do any kind of computation.Under the immediate words, the Computer is made out of "Compute" which signifies, "Calculate". Thusly, Computers are a computing machine.Modern computers have the ability to follow generalized sets of operations, called programs. These programs enable computers to perform an extremely wide range of tasks. A "complete" computer including the hardware, the operating system (main software), and peripheral equipment required and used for "full" operation can be referred to as a computer system. This term may as well be used for a group of computers that are connected and work together, in particular a computer network or computer cluster.

Computers are used as control systems for a wide variety of industrial and consumer devices. This includes simple special purpose devices like microwave ovens and remote controls, factory devices such as industrial robots and computer-aided design, and also general purpose devices like personal computers and mobile devices such as smartphones. The Internet is run on computers and it connects hundreds of millions of other computers and their user. A computer is an electronic device, which stores data and processes information based upon the instructions provided by the user and generates the desired output.A computer is a device that computes or calculates numbers, however, does more than that. It can edit text, generate pictures or graphs, make animation, translate language and even play games or drive motor cars etc.

FUNCTIONAL COMPONENTS The computer has following components:  Input Unit:  CPU (): CU & ALU  Memory  Output Unit Every function is represented by a number in the figure: The data and instructions read by the input unit are sent to the CPU. The CPU stores the instructions and data into primary or main memory. As the main memory is volatile in nature and smaller in size, the input data and instructions are stored into secondary memory for permanent storage. The data or instructions are sent back to main memory, when they are required by CPU for processing. The data or instructions are sent to CPU for processing. The data is sent into ALU for arithmetic and logical operations.

The result obtained after processing is sent to main memory. If some error occurs, CPU displays error message on the output device.

The result is sent to output device for displaying.

A computer is a machine that can be instructed to carry out sequences of arithmetic or logical operations automatically via computer programming. Modern computers have the ability to follow generalized sets of operations, called programs. These programs enable computers to perform an extremely wide range of tasks. A "complete" computer including the hardware, the operating system (main software), and peripheral equipment required and used for "full" operation can be referred to as a computer system. This term may as well be used for a group of computers that are connected and work together, in particular a computer network or computer cluster. Computers are used as control systems for a wide variety of industrial and consumer devices. This includes simple special purpose devices like microwave ovens and remote controls, factory devices such as industrial robots and computer-aided design, and also general purpose devices like personal computers and mobile devices such as smartphones. The Internet is run on computers and it connects hundreds of millions of other computers and their users. Early computers were only conceived as calculating devices. Since ancient times, simple manual devices like the abacus aided people in doing calculations. Early in the Industrial Revolution, some mechanical devices were built to automate long tedious tasks, such as guiding patterns for looms. More sophisticated electrical machines did specialized analog calculations in the early 20th century. The first digital electronic calculating machines were developed during World War II. The first semiconductor transistors in the late 1940s were followed by the silicon-based MOSFET (MOS transistor) and monolithic (IC) chip technologies in the late 1950s, leading to the and the microcomputer revolution in the 1970s. The speed, power and versatility of computers have been increasing dramatically ever since then, with MOS transistor counts increasing at a rapid pace (as predicted by Moore's law), leading to the Digital Revolution during the late 20th to early 21st centuries. Conventionally, a modern computer consists of at least one processing element, typically a central processing unit (CPU) in the form of a metal-oxide-semiconductor (MOS) microprocessor, along with some type of computer memory, typically MOS semiconductor memory chips. The processing element carries out arithmetic and logical operations, and a sequencing and can change the order of operations in response to stored information. Peripheral devices include input devices (keyboards, mice, joystick, etc.), output devices (monitor screens, printers, etc.), and input/output devices that perform both functions (e.g., the 2000s-era touchscreen). Peripheral devices allow information to be retrieved from an external source and they enable the result of operations to be saved and retrieved.

Classification Of Computer (Different Types Of Computer)

Classification of Computer According to Size

Micro computer

It is the smallest type of computer. Inside a micro computer the ALU and CU are combined on a single chip called microprocessor. They are used as home computers or by small businessmen or individual professional where volumes of data processing and speed requirement are small.

Mini computers

Mini computers are more powerful than the micro computers and can support several users. They have large RAM and backing storage capacity and can data more quickly.

Main Frame computers

Main Frame computers are very large computers with very high capacity of main store. They can process large amounts of data very quickly. So they are used by banks, big companies and govt departments. They can be linked into a network with smaller departmental computers, etc.

Super Computers

Super Computers are used for complex scientific computations are known as super computers. Very large size and very high speeds characterize them. The word length for these computers is more than 64 . They have more than one processing unit and perform parallel processing. Storage capacities of these computers are very large. They are used in weather forecasting, in nuclear power plants etc.

Classification of Computer According to Application a) b) Digital Computer c) Hybrid Computer

Analog computers work on the principle of continuous measurement of physical phenomenon like length, breadth, rotation etc. It deals with continuous data and does not communicate directly with numbers. It uses signals as input and output in terms of actions or environmental/ conditional changes (Speed, Temp, Moisture). These are faster than hybrid computers but less accurate. During the first half of the 20th century, many scientific computing needs were met by increasingly sophisticated analog computers, which used a direct mechanical or electrical model of the problem as a basis for computation. However, these were not programmable and generally lacked the versatility and accuracy of modern digital computers.[19] The first modern analog computer was a tide-predicting machine, invented by Sir William Thomson in 1872. The differential analyser, a mechanical analog computer designed to solve differential equations by integration using wheel-and- disc mechanisms, was conceptualized in 1876 by James Thomson, the brother of the more famous Lord Kelvin.[15] The art of mechanical analog computing reached its zenith with the differential analyzer, built by H. L. Hazen and Vannevar Bush at MIT starting in 1927. This built on the mechanical integrators of James Thomson and the torque amplifiers invented by H. W. Nieman. A dozen of these devices were built before their obsolescence became obvious. By the 1950s, the success of digital electronic computers had spelled the end for most analog computing machines, but analog computers remained in use during the 1950s in some specialized applications such as education (control systems) and aircraft (slide rule).

Digital computers

By 1938, the United States Navy had developed an electromechanical analog computer small enough to use aboard a submarine. This was the Torpedo Data Computer, which used trigonometry to solve the problem of firing a torpedo at a moving target. During World War II similar devices were developed in other countries as well.

Early digital computers were electromechanical; electric drove mechanical relays to perform the calculation. These devices had a low operating speed and were eventually superseded by much faster all-electric computers, originally using vacuum tubes. The , created by German engineer in 1939, was one of the earliest examples of an electromechanical computer.[20] In 1941, Zuse followed his earlier machine up with the Z3, the world's first working electromechanical programmable, fully automatic digital computer.[21][22] The Z3 was built with 2000 relays, implementing a 22 word length that operated at a clock frequency of about 5–10 Hz.[23] Program code was supplied on punched film while data could be stored in 64 words of memory or supplied from the keyboard. It was quite similar to modern machines in some respects, pioneering numerous advances such as floating point numbers. Rather than the harder-to-implement decimal system (used in Charles Babbage's earlier design), using a binary system meant that Zuse's machines were easier to build and potentially more reliable, given the technologies available at that time.

Hybrid computers

Hybrid computers are those in which the features of Analog and Digital machines are combined to create a hybrid computing system

3. Classification of Computer According to Purpose a) General Purpose Computer b) Special Purpose Computer

General purpose computers

General purpose computers are versatile and can be used in numerous of applications. These are the home pc’s which can be used to play, study, watch music ad movies etc.

Special purpose computers

Special purpose computers are designed to perform a specific task. These computers are not versatile in nature and cannot be used for some other purpose than specified. Ex: fight simulation training programme

Basic characteristics about computer

 Speed: - As you know computer can work very fast. It takes only few seconds for calculations that we take hours to complete. You will be surprised to know that computer can perform millions (1,000,000) of instructions and even more per second.  Therefore, we determine the speed of computer in terms of microsecond (10-6 part of a second) or nanosecond (10 to the power -9 part of a second). From this you can imagine how fast your computer performs work.  Accuracy: - The degree of accuracy of computer is very high and every calculation is performed with the same accuracy. The accuracy level is 7.  determined on the basis of design of computer. The errors in computer are due to human and inaccurate data.  Diligence: - A computer is free from tiredness, lack of concentration, fatigue, etc. It can work for hours without creating any error. If millions of calculations are to be performed, a computer will perform every calculation with the same accuracy. Due to this capability it overpowers human being in routine type of work.  Versatility: - It means the capacity to perform completely different type of work. You may use your computer to prepare payroll slips. Next moment you may use it for inventory management or to prepare electric bills.  Power of Remembering: - Computer has the power of storing any amount of information or data. Any information can be stored and recalled as long as you require it, for any numbers of years. It depends entirely upon you how much data you want to store in a computer and when to lose or retrieve these data.  No IQ: - Computer is a dumb machine and it cannot do any work without instruction from the user. It performs the instructions at tremendous speed and with accuracy. It is you to decide what you want to do and in what sequence. So a computer cannot take its own decision as you can.  No Feeling: - It does not have feelings or emotion, taste, knowledge and experience. Thus it does not get tired even after long hours of work. It does not distinguish between users.  Storage: - The Computer has an in-built memory where it can store a large amount of data. You can also store data in secondary storage devices such as floppies, which can be kept outside your computer and can be carried to other computers.

FUNCTIONAL UNITS

In order to carry out the operations mentioned in the previous section the computer allocates the task between its various functional units. The computer system is divided into three separate units for its operation. They are

Arithmetic Logical Unit (ALU)

Logical Unit :After you enter data through the input device it is stored in the primary storage unit. The actual processing of the data and instruction are performed by Arithmetic Logical Unit. The major operations performed by the ALU are addition, subtraction, multiplication, division, logic and comparison. Data is transferred to ALU from storage unit when required. After processing the output is returned back to storage unit for further processing or getting stored.

Control Unit (CU)

The next component of computer is the Control Unit, which acts like the supervisor seeing that things are done in proper fashion. Control Unit is responsible for co ordinating various operations using time signal. The control unit determines the sequence in which computer programs and instructions are executed. Things like processing of programs stored in the main memory, interpretation of the instructions and issuing of signals for other units of the computer to execute them. It also acts as a board operator when several users access the computer simultaneously. Thereby it coordinates the activities of computer’s peripheral equipment as they perform the input and output.

Central Processing Unit (CPU)

The ALU and the CU of a computer system are jointly known as the central processing unit. You may call CPU as the brain of any computer system. It is just like brain that takes all major decisions, makes all sorts of calculations and directs different parts of the computer functions by activating and controlling the operations.

Computer operation 1. Input: This is the process of entering data and programs in to the computer system. You should know that computer is an electronic machine like any other machine which takes as inputs raw data and performs some processing giving out processed data. Therefore, the input unit takes data from us to the computer in an organized manner for processing. 2. Storage: The process of saving data and instructions permanently is known as storage. Data has to be fed into the system before the actual processing starts. It is because the processing speed of Central Processing Unit (CPU) is so fast that the data has to be provided to CPU with the same speed. Therefore the data is first stored in the storage unit for faster access and processing. This storage unit or the primary storage of the computer system is designed to do the above functionality. It provides space for storing data and instructions. The storage unit performs the following major functions: • All data and instructions are stored here before and after processing. • Intermediate results of processing are also stored here. 3. Processing: The task of performing operations like arithmetic and logical operations is called processing. The Central Processing Unit (CPU) takes data and instructions from the storage unit and makes all sorts of calculations based on the instructions given and the type of data provided. It is then sent back to the storage unit. 4. Output: This is the process of producing results from the data for getting useful information. Similarly the output produced by the computer after processing must also be kept somewhere inside the computer before being given to you in human readable form. Again the output is also stored inside the computer for further processing. 5. Control: The manner how instructions are executed and the above operations are performed. Controlling of all operations like input, processing and output are performed by control unit. It takes care of step by step processing of all operations inside the computer.

ADVANTAGES OF USING COMPUTERS

For Writing:

 Quick Entry  Easy to edit and restructure  Many tools to produce various kinds of output  Storage is inexpensive and dosen’t take up much space  Easy to search/navigate through documents.

For Organization:

 Once a document is in electronic form it is easy to store and many documents can be stored on one computer in much less space.  Files are easy to reach  Data storage, analyzing and decision making.

For Research:

 Access to the Internet has become invaluable as a research tool.  Easily gather huge amounts of information and store it.  Easily search for new information or search the information already acquired.  Interact with other researchers to create/gather more research.  Easily interpret results of own search

At Home:

 Entertainment by playing games, watching videos and listening music etc.  Chatting with your relatives and friends.

Education:

 Collecting information from Internet.  Making programs to solve problems.

LIMITATIONS OF COMPUTERS

 A computer cannot think itself. It has no self intelligence.  A computer cannot learn by experience like a human being.  A computer cannot take independent decisions. . . MEMORY

Memory is used to store data and information and instructions to be executed. When we talked about memory we mean main and secondary memory. Few fundamentals Memory Cell: An electrical circuit or device use to store a single bit or binary digit (0,1). This is the basic unit of information storage. Memory Word: A group of memory cells in a memory that represents instructions or data is known as memory word. Nibble: A group of 4 bits is called nibble. Byte: A group of 8 bits is called 1 byte. Word length: The number of bits in a memory word is known as word length. Memory Capacity: It is a way of specifying that how many bits can be stored in a particular memory device or complete memory system. 1 Byte = 8 bits 1 KB = 1024 Bytes 1 MB = 1024 KB 1 GB = 1024 MB Memory Address: A number that identifies the location of a word in memory is called its memory address. Each word stored in a memory device or system has a unique address.

TYPES OF MAIN MEMORY

RAM : (Random Access Memory) – It is a part of main memory. It is temporary or volatile in nature. All the data and programs loaded into the memory are lost as the power is switched off. There are two types of RAM Dynamic RAM: The most common type of computer memory also known as D RAM. It usually use one transistor and a capacitor to represent a bit. Static RAM: A type of RAM that is quicker than dynamic RAM and does not need to be refreshed frequently. It also requires power to hold its contents. It is made up of a pretzel-like flip-flop circuit that lets current flow through one side or the other based on which one of the two transistors are activated. ROM: (Read Only Memory) – It is also the part of Primary or Main Memory. But it is not volatile in nature like RAM. It means that the contents of this type of memory remains even the power is switched off. The data can be used for reading only. Any change into the contents of ROM is not possible. The various types of ROM are: 1. PROM: (Programmable Read Only Memory) – It may be programmed by the programmer by a special device called PROM programmer. It is also permanent and hence no alteration is possible after once written. 2. EPROM: (Erasable Programmable Read Only Memory) – It is programmable ROM, which may be programmed again and again. It is semi permanent. Exposing it to ultra violet light erases it. 3. EEPROM: (Electrically Erasable Programmable Read Only Memory) – It is same as EPROM, the only difference is that electric signals are used to erase the contents instead of Ultra violet light. 4. Flash Memory – It is a special type of EEPROM that can be erased and programmed in blocks instead of one byte at a time. 5. Masked ROM – It is manufactured by masking and metallization process. The pattern or matrix once created is permanent. No change or alteration is possible after once written.

HARDWARE

It is the electric, electronic and mechanical equipment that makes up a computer. All physical parts that we can touch are called hardware parts. Different Hardware parts are:  Input Device – It is any hardware component that allows a user to enter data and instructions into a computer. Some commonly used input devices are: 1. Keyboard: They are one of the most important input devices for a computer. It is used to type in letters, numbers and other characters. The layout of keyboard or a keyboard consists of 1. Typing keys 2. Numeric Keypad 3. Function Keys 4. Control Keys Mouse: It is a pointing device, which is quite handy for many visual applications. It is the most common type of input device after the keyboard. It has a long wire connected to the computer, therefore it is called mouse. Microphone: It is the device by which the data is input by speaking on the mic. Scanner: It is the device by which a document can be scanned by the device called a scanner. Digital Camera PC Camera Joystick Light Pen Trackball

Output Device:

They are the device by which the user can get the output by the computer. Various output devices are: 1. Monitor/VDU 2. Printer: There are two types of printers  Impact Printer 1. Drum Printer 2. Daisy wheel Printer 3. DOT Matrix Printer  Non Impact Printer 1. Ink Jet Printer 2. Laser Printer 3. CPU: Central Processing Unit 4. Control Unit 5. Memory  System Unit: It is a box like shaped case made from metal or plastic that protects the internal electronic components of the computer from damage.  Storage Device: It records and retrieves data to and from a storage medium. Some common storage devices are floppy disk drives, Zip Drives, hard disk drives, CD-ROM device, CD-RW Device, DVD-ROM Device, etc.  Communication Device: It enables computer users to communicate and exchange items such as data, instructions and information with another computer.

SOFTWARE

Software gives “intelligence” to the computer. The hardware alone cannot perform calculations without being instructed exactly what to do ad how to do it.  System Software: It consists of the programs that control the operations of a computer and its devices. As the name implies these programs or software are related to the computer system. It consists of all programs, languages, documentation supplied by the manufacturer with the computer and to develop their own programs.  Language : We input the data and instructions into the computer usually in English. But computer understands only the language of 0 & 1 (Binary Language) so the Language Processor changes or converts the language of the user Hindi or English into machine language.  Assembler: The assembler converts the programs written in assembly language into machine language. An assembly language is a language that is coded form of machine language into symbolic codes of English alphabet.  Compiler: A compiler converts a High level language into machine language. It is translator that reads the full program locate errors and translates it into machine language.  Interpreter: One more type of translator is used to convert high level language into machine language. It takes one statement at a time and executes appropriate instructions leading to the same computations as required by that line of code. 

 Operating System

The 1960’s definition of an operating system is “the software that controls the hardware”. However, today, due to we need a better definition. We see an operating system as the programs that make the hardware useable. In brief, an operating system is the set of programs that controls a computer. Some examples of operating systems are UNIX, Mach, MS-DOS, MS-Windows, Windows/NT, Chicago, OS/2, MacOS, VMS, MVS, and VM. Operating Systems are resource managers. The main resource is computer hardware in the form of processors, storage, input/output devices, communication devices, and data. Some of the operating system functions are: implementing the user interface, sharing hardware among users, allowing users to share data among themselves, preventing users from interfering with one another, scheduling resources among users, facilitating input/output, recovering from errors, accounting for resource usage, facilitating parallel operations, organizing data for secure and rapid access, and handling network communications.

Objectives of Operating Systems

Modern Operating systems generally have following three major goals. Operating systems generally accomplish these goals by running processes in low privilege and providing service calls that invoke the operating system kernel in high-privilege state.  To hide details of hardware by creating abstraction An abstraction is software that hides lower level details and provides a set of higher- level functions. An operating system transforms the physical world of devices, instructions, memory, and time into virtual world that is the result of abstractions built by the operating system. There are several reasons for abstraction. First, the code needed to control peripheral devices is not standardized. Operating systems provide subroutines called device drivers that perform operations on behalf of programs for example, input/output operations. Second, the operating system introduces new functions as it abstracts the hardware. For instance, operating system introduces the file abstraction so that programs do not have to deal with disks. Third, the operating system transforms the computer hardware into multiple virtual computers, each belonging to a different program. Each program that is running is called a process. Each process views the hardware through the lens of abstraction. Fourth, the operating system can enforce security through abstraction.  To allocate resources to processes (Manage resources) An operating system controls how processes (the active agents) may access resources (passive entities).  Provide a pleasant and effective user interface The user interacts with the operating systems through the user interface and usually interested in the “look and feel” of the operating system. The most important components of the user interface are the command interpreter, the file system, on-line help, and application integration. The recent trend has been toward increasingly integrated graphical user interfaces that encompass the activities of multiple processes on networks of computers. One can view Operating Systems from two points of views: Resource manager and Extended machines. Form Resource manager point of view Operating Systems manage the different parts of the system efficiently and from extended machines point of view Operating Systems provide a virtual machine to users that is more convenient to use. The structurally Operating Systems can be design as a monolithic system, a hierarchy of layers, a virtual machine system, an exokernel, or using the client- server model. The basic concepts of Operating Systems are processes, memory management, I/O management, the file systems, and security.

Types of Operating Systems

Within the broad family of operating systems, there are generally four types, categorized based on the types of computers they control and the sort of applications they support. The categories are:  Real-time operating system (RTOS) – Real-time operating systems are used to control machinery, scientific instruments and industrial systems. An RTOS typically has very little user-interface capability, and no end-user utilities, since the system will be a “sealed box” when delivered for use. A very important part of an RTOS is managing the resources of the computer so that a particular operation executes in precisely the same amount of time, every time it occurs. In a complex machine, having a part move more quickly just because system resources are available may be just as catastrophic as having it not move at all because the system is busy.  Single-user, single task – As the name implies, this operating system is designed to manage the computer so that one user can effectively do one thing at a time. The Palm OS for Palm handheld computers is a good example of a modern single-user, single-task operating system.  Single-user, multi-tasking – This is the type of operating system most people use on their desktop and laptop computers today. Microsoft’s Windows and Apple’s MacOS platforms are both examples of operating systems that will let a single user have several programs in operation at the same time. For example, it’s entirely possible for a Windows user to be writing a note in a word processor while downloading a file from the Internet while printing the text of an e-mail message.  Multi-user – A multi-user operating system allows many different users to take advantage of the computer’s resources simultaneously. The operating system must make sure that the requirements of the various users are balanced, and that each of the programs they are using has sufficient and separate resources so that a problem with one user doesn’t affect the entire community of users. Unix, VMS and mainframe operating systems, such as MVS, are examples of multi-user operating systems.