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## Thursday, September 21, 2017

### Introduction to Computers an Number System

Unit – 3: Introduction to Computer and Number System
Meaning of Computer
The term ‘computer’ usually refers to an electronic device made of electronic circuits which processes data into meaningful information under the control of specific step-by-step instruction arranged as a program. It perform many functions such as calculation, storage, manipulation & retrieval of information. The key characteristics (or advantages) of a computer are:
1. Speed: The speed of a computer is usually measured in milliseconds, microseconds, nanoseconds and picoseconds which are,,andpart of a second respectively.
2. Accuracy: Errors do occur in computer based information systems but precious few can be directly attributed to the computer system itself. The vast majority can be traced to a program which is mainly human errors.
3. Capacity of Decision Making: By suitable programming, computers can also perform intelligent functions of decision making.
4. Reliability: The system does repetitive work with huge volumes of data correctly. One can rely on them to work non-stop, keeping a backup of data and also an Uninterrupted Power Supply (UPS).
5. Memory Capability: Computer systems have total instant recall of data and an almost unlimited capacity to store these data. A computer system can hold billion characters at a time can be retrieved at random.
a. Speed: The smallest unit of time that a human being can experience is second. But Computer operations are measured in milliseconds, microseconds, nanoseconds and picoseconds. Today computers can perform more than 2500 MIPS. They can handle very complex tasks in seconds.

b. Accuracy: Errors occur in computers also but only few errors can be attributed (=credited) to a computer. In most of the cases errors occur due to program logic error, procedural error or erroneous data. Really speaking, these are human errors.
c. Reliability: Computers can perform repetitive tasks very well. They don’t take sick days and coffee breaks and they rarely make any complaints. Even the error rate of 0.1% is unacceptable.
d. Memory capability: Computer systems can instantly recall the data and their storage capacity is almost unlimited. Today, even ordinary personal computers are coming with 10 to 40 GB of memory. High end computers can support still more memory.
e. Flexibility: Modern digital computers can be used for a variety of purposes and everything depends on the program inside the computer.
f. Choice of configuration: A wide range of optional peripherals are available in the market. A business organisation can select those peripherals which are most suitable for its processing requirements.
Limitations of computer system
The limitations of compute are as follows:
1. GIGO: Garbage in Garbage Out i.e. computer does not have its own IQ and an incorrect input data would result in an incorrect output. The computer does what it is programmed to do and can do nothing else.
2. Limitations of Software: To perform specialized functions, special software is required. The investment in software is much more than in hardware.
3. Tampering of Data: Data handling through computers require special protection routines.
4. Limitations of Hardware: Smaller computers can perform relatively limited work at a slower speed. So more investments is to be required for higher speed computers.
Components of a Computer System

Secondary Storage (disk)
Components of Computer System

1. Input 2. CPU (Central Processing Unit) 3. Output 4. Storage
2. (a) Control Unit 2. (b) A.L.U 4. (a) Primary 4. (b) Secondary
1. Input:
1. Entry of program statement & data into a computer is done by means of an input device.
2. Keyboard, floppy, disk drives, cartridge tape device are the various input devices.
3. All input devices are instruments of interpretation and communication between people and computer.
1. CPU:
1. Is the heart of the computer?
2. It contains the logic that controls the calculation doe by the computer.
3. It is the central processor that makes comparisons, performs calculations, reads, interprets & controls the execution of the instructions.
4. The CPU consists of two separate sub-units –
1. Control unit
2. Arithmetic logic unit.
In the PC, the CPU is connected to a bus; the bus is a communication device or in other words a connection between various parts of the computer.
1. Control Unit:
1. Supervises the operations of entire computer,
2. Acts as a Central Nervous System by maintaining the order & directing the flow of sequence of operation & data within the computer,
3. It selects the program statement from the storage unit, interprets the statement & sends the appropriate electronic impulses to Arithmetic/Logic and storage units which carries out the required operation.
4. Its basic function is to instruct the input device, when to start & stop transferring data to output devices.
1. ALU:
1. Performs calculation, compares numeric & Non-numeric values & make decisions.
2. Data is transferred from the storage unit to ALU which is again manipulated & returned to storage unit.
1. Output Devices:
1. Are instruments that communicate between users & machine?
2. Meant for presenting results.
3. Translates computer output in user understandable form.
4. Printer, VDU, Graph-Plotters are the output devices.
5. Captures information in machine coded form & converts them into a form usable by humans computers.
1. Storage:
1. Primary:
• Has no logic capability and is one a storage unit for data and instruction.
• It is passive in nature. Memory is only a storage place for information. Instructions are executed in CPU. Data are moved between the CPU and memory when a calculation is performed.
1. Secondary: (Diskette drive, disk etc.)
• Are machines & are connected online to CPU and serve as reference libraries?
• Used as a store house & used only when necessary.
• Magnetic tapes, Floppy, H.D. CDS etc. are the devices.
• Usually larger and cheaper than Primary.
Computer Generations
The computers have been grouped into chronological categories, called generations. Computer generation means a step of advancement in technology. It also reflects the growth of computer industry. The advancement in technology existed not only in hardware but also in software. The evolution of modern computer is divided in different generations as below:
1. First Generation: The first generation of computers was developed in late 1940s. In this generation of computers, vacuum tubes were used and these were bulky in size.
2. Second Generation: In the generation of computers, solid state devices called transistors, diodes etc. were developed by William Shockley and colleagues at Bell laboratories. These solid state devices were used in place of vacuum tubes. This replacement increased the speed of computers and other drawbacks were reduced. Second generation computers were smaller in size, cheaper in manufacturing. These computers occupied lesser space and consumed lesser power.
3. Third Generation: These computers have secondary storage devices and new input and output devices like visual display terminals, magnetic ink readers and high speed printers, integrated solid state circuit (IC chips). I.C. chips increased the speed of these computers. These computers performed the arithmetic and logic operations in micro- seconds (Millionths of a second) or even in nano-second (Billionths of a second). The size and cost of these computers have decreased considerably.
4. Fourth Generation: Integrated Circuits Technology was further developed. In 1971, INTEL Corp. of USA developed the IC chips which have the entire computer circuit on a single silicon chip. These chips are called microprocessors. These microprocessors gave birth to micro-computers called micro-processors. In 1976, Steve Wozniak developed a series of micro-computers called .The Allple Series.. These computers were the most modern computers. These were much cheaper relative to performance in comparison to early computers.
5. Fifth Generation: Fifth generation computers are those computers, which not only have the advanced capabilities like speed, accuracy, storage and retrieval capabilities of other computers but have also additional ability to think and make decisions. The ability of intelligence in computers is called Artificial Intelligence (AI). Japanese have named this generation of computers as KIPS (Knowledge Information on Processing System).
Different Types of Computers
Since the advent of the first computer different types and sizes of computers are offering different services. Computers can be as big as occupying a large building and as small as a laptop or a microcontroller in mobile & embedded systems. The four basic types of computers are as under:
1. Supercomputer
2. Mainframe Computer
3. Minicomputer
4. Microcomputer
1. Supercomputer: The most powerful computers in terms of performance and data processing are the Supercomputers. These are specialized and task specific computers used by large organizations. These computers are used for research and exploration purposes, like NASA uses supercomputers for launching space shuttles, controlling them and for space exploration purpose.
2. Mainframe computer: Although Mainframes are not as powerful as supercomputers, but certainly they are quite expensive nonetheless, and many large firms & government organizations uses Mainframes to run their business operations. The Mainframe computers can be accommodated in large air-conditioned rooms because of its size. Super-computers are the fastest computers with large data storage capacity, Mainframes can also process & store large amount of data. Banks educational institutions & insurance companies use mainframe computers to store data about their customers, students & insurance policy holders.
3. Minicomputer: Minicomputers are used by small businesses & firms. Minicomputers are also called as “Midrange Computers”. These are small machines and can be accommodated on a disk with not as processing and data storage capabilities as super-computers & MainframesThese computers are not designed for a single user. Individual departments of a large company or organizations use Mini-computers for specific purposes. For example, a production department can use Mini-computers for monitoring certain production process.
4. Microcomputer: Desktop computers, laptops, personal digital assistant (PDA), tablets & smartphones are all types of microcomputers. The micro-computers are widely used & the fastest growing computers. These computers are the cheapest among the other three types of computers. The Micro-computers are specially designed for general usage like entertainment, education and work purposes. Well known manufacturers of Micro-computer are Dell, Apple, Samsung, Sony & Toshiba.
Desktop computers, Gaming consoles, Sound & Navigation system of a car, Netbooks, Notebooks, PDA’s, Tablet PC’s, Smartphones, Calculators are all type of Microcomputers.
Types of memory in a Computer
1) Primary memory
2) Secondary memory
1) Primary memory: It is directly accessible by the CPU. The primary memory is of two types such as
a) ROM memory
2) Secondary memory: The maximum capacity of primary memory is limited. So to handle more data than allowed by primary memory, secondary memory is used. And it is non-volatile i.e. data is not lost due to current failure. Magnetic tape, Floppy disk and Hard disk are some examples of secondary memory.
Software and its Types
Meaning: A set of instructions (in machine code) given to the computer to solve user problems and to control different operations of the computer is known as computer software. The software is developed in programming languages. The Computer software is classified into two main categories:
1. Application software.
2. System software.
1. Application Software: A set of programs used to solve particular problems of user through computer is called Application software. It is also known as application package. Some of application packages are:

a) Word processing software.
c) Database Management System software.
d) Graphics software.
e) Communication software.
2. System Software: System software is a set of programs that control the operations of a computer and devices attached with the computer. It creates links between user and computer as well as controls the execution of application programs. The examples of system software are:
a) Operating systems.
b) Utility programs.
c) Device Drivers.
d) Language Processors.
Hardware
Hardware is best described as a device, such as a hard drive, that is physically connected to the computer or something that can be physically touched. A CD-ROM, computer display monitor, printer, and video card are all examples of computer hardware. Without any hardware, a computer would not function, and software would have nothing to run on. Hardware and software interact with one another: software tells hardware which tasks it needs to perform.
Types of Hardware:
Input devices – keyboard, image scanner, microphone, pointing device, graphics tablet, joystick, light pen, mouse, touchpad, touchscreen, trackball,  webcam
Output devices – monitor, printer, speakers
Removable data storage - optical disc drive (CD-RW, DVD+RW), floppy disk, memory card, USB flash drive
Computer case - central processing unit (CPU), hard disk, motherboard, network interface controller, power supply, random-access memory (RAM), sound card, video card
Data ports - Ethernet firewire, parallel port, serial port, universal serial bus (USB)
There are several differences between computer hardware and software.

Operating system and Its types
An operating system (OS) is software, consisting of programs and data that runs on computers and manages computer hardware resources and provides common services for efficient execution of various application software.
Types of operating systems:
1. Real-time Operating System: It is a multitasking operating system that aims at executing real-time applications. The main object of real-time operating systems is their quick and predictable response to events.
2. Multi-user and Single-user Operating Systems: The operating systems of this type allow a multiple users to access a computer system concurrently. Time-sharing system can be classified as multi-user systems as they enable a multiple user access to a computer through the sharing of time. Single-user operating systems, as opposed to a multi-user operating system, are usable by a single user at a time.
3. Multi-tasking and Single-tasking Operating Systems: When a single program is allowed to run at a time, the system is grouped under a single-tasking system, while in case the operating system allows the execution of multiple tasks at one time, it is classified as a multi-tasking operating system.
4. Distributed Operating System: An operating system that manages a group of independent computers and makes them appear to be a single computer is known as a distributed operating system. The development of networked computers that could be linked and communicate with each other, gave rise to distributed computing.
5. Embedded System: The operating systems designed for being used in embedded computer systems are known as embedded operating systems. They are designed to operate on small machines like PDAs with less autonomy.
Meaning of Data and Information
Data: The word “data’ (plural of “datum”) is used generally both in singular and plural form. Data includes raw materials or facts or observation about business transactions or physical phenomena that are processed into finished information products. It is, thus, an objective measurement of attributes of entities, viz. people, places, things and events. It constitutes a valuable organizational resource which must be managed efficiently, so that all end users in an organization are benefitted. Data may be in any of following forms:
1. Traditional alphanumeric data: It is composed of numbers, alphabets and other characters.
2. Text data: It consists of sentences and paragraphs.
3. Image data: It consists of graphic shapes and figures.
4. Audio data: It consists of human voice and other sounds.
5. Video data: It consists of visual image and figures.
Data are needed to supply required information. Data are treated as raw materials to furnish finished products in the form of information. Data are viewed by manager and information systems professionals as data resources which are typically organized into:
1. Data bases to hold processed and organized data.
2. Knowledge bases to hold knowledge in various forms.
Information: Information refers to the data that have been put into a meaningful and useful context for specific end users. In the words of Davis and Olson, “Information is data that has been processed into a form that is meaningful to the recipient and is of real or perceived value in current or progressive decision.” Information are basic resource and substance on which business decisions are based. The need for information arises on account of:
1. Survival of business: Information is needed for survival of a business.
2. Basis for decisions: It is the substance on which business decisions are based.
3. Framework for information system: It provides framework for information system in an organization.
4. Basis for various system: It is the finished product which provides basis for various system in an organization.
Difference between Data and Information
 Basic Data Information Meaning Data are raw facts or observations or assumptions or occurrence about physical phenomenon or business transaction. It is the data that has been converted into a meaningful and useful context for specific end users. Origin They are objective measurement of attributes (characteristics) of entities (like people, place, things, and events) To obtain information data’s form is aggregated, manipulated and organized, its content analyzed & evaluated & placed in proper context for human use. Organization Data is a collection of facts, which is unorganized but can be organized into useful information. Information exists as reports, in a systematic textual format, or as graphics in an organized manner. Properties Data should be accurate but need not be relevant, timely or concise. Information must be relevant, timely accurate, concise and complete and should apply to the current situation. Forms to exist It can exist in different forms e.g. picture, text, sound, or all of these together. It should be condensed into usable length.

VARIOUS TYPES OF NUMBER SYSTEMS
The knowledge of number systems is very essential because the design and organization of a computer is dependent upon the number systems. The various number systems discussed are:
1. Decimal Number System.
2. Binary Number System.
3. Octal Number System.
1. Decimal Number System: The decimal number system consists of 10 digits namely 0 to 9. In decimal system each digit has a digit value from 0 to 9. Each digit also has a positional value determined by how many places to the left or the right of the decimal point the digit is written. Digit value and positional value for each number system depend on the base of the number system. Positional values are in increasing powers of the base as we move left and decreasing powers of the base as we move right.
2. Binary Number System: Binary numbers play a very important role in design, organization and understanding of computers. The binary number system, as the name suggests, consists of two digits namely, 0 and 1 and is exactly like the decimal system except that the base is 2 instead of 10. Again this code is used only for mathematical applications and is not intended to handle alphabetic data. Since the binary system only uses two symbols (1, 0), it called a base-two system. This means that starting from the low-order position (right-most), successive positions represent successively higher powers of the base two as we move to the left (or higher-order position). the reasons why binary numbers are used for computers are as under:
• Computer circuits have to handle only two binary digits rather than 10. This simplifies design, reduces cost and improves reliability.
• Electronic components by their very nature operate in a binary mode. A switch is either (1) or off (0), or again, a transistor is either conducting (1) or non-conducting (0).
• Every thing that can be done with the base of 10 can equally be done when the base is 2.
1. Octal Number System: Since binary numbers are long and cumbersome, more convenient representations combine groups of three or four bits into octal (base 8) digits respectively. In octal number, there are only eight possible digits (0 to 7). The position of a digit to the left of the octal point carries a Weightage in ascending powers of eight. Digits behind the octal points are also used (octal points are similar to decimal and binary points are used to separate whole and fractional parts) and carry Weightage of. This system is more popular with microprocessors because the number represented in octal system can be used directly for input and output operations.
2. Hexadecimal Number System: The hexadecimal number system popularly known as Hex system is similar to octal system with the exception that the base is 16 and three must be 16 digits. This system is very well suited for big computers such as belonging to IBM (International Business Machines) series or Honeywell etc. The most commonly used microprocessors having CPU chips as INTEL, 8085 prefer this number system. The hexadecimal number system represents an information in the concise form. The sixteen symbols used in this system are, decimal digits 0 to 9 and alphabets A to F. The equivalence between hex-numbers, (numbers represented in Hexadecimal system) binary and decimal numbers as given below:
 Decimal Value Hexa Digits Binary Equivalent Decimal Value Hexa Digit Binary Equivalent 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0000 0001 0010 0011 0110 0101 0110 0111 8 9 10 11 12 13 14 15 8 9 A B C D E F 1000 1001 1010 1011 1100 1101 1110 1111

COMPUTER CODING SYSTEMS
Computers work on binary system whereas decimal number system is accepted as the international system. English is taken as the international contact language. On the other hand, computers understand only binary language i.e. the language of 0 and 1. In order to talk to computers one has to convert the information, numeric or non-numeric, into binary language. This is precisely known as Coding. Coding is the process of representation of numeric or non-numeric information in terms of binary digits. The process of conversion of numeric quantities into their binary equivalents has been discussed earlier. By using different bit patterns the non-numeric information, such as letters of English alphabet A – Z can be represented. For example, the letter A is represented by the bit pattern, 110001 and similarly an equal (=) sign is represented as 001011. There are various codes to represent the data. A few of these are Binary BCD, ASCII or EBCDIC etc. The details of these codes are discussed below. Coding the computers is done to achieve the following objectives.
1. To convert numeric and alphanumeric information in terms of binary digits 0 and 1.
2. To transmit correct data to the computer and also to detect and correct errors, if any, in transmission of data.
Binary Coded Decimal System (BCD)
BCD stands for Binary Coded Decimal. For representing decimal number to binary, BCD codes are used. The appropriate 4 – bit code replaces decimal number in BCD codes. If in a binary code, number carries certain weight, it is known as weighted binary code. Nibble refers to a string of 4 bits. By BCD, we mean that each decimal digit is represented by a nibble. The most leading BCD code is 8421 code, which indicates weight of 4 bits. Although 4 bits can represent 16 numbers (24), only 10 are used and rest 6 are invalid.
The uses or advantages of BCD code are:
• For representing decimal number to binary, BCD codes are used.
• BCD code finds its use in pocket calculator, digital clock, etc.
• BCD codes were used in early version of computer.
The disadvantages of BCD code are:
• BCD code is slower than binary system.
• BCD code is more complicated than binary system.
American Standard Code for Information Interchange (ASCII)
The computers had started using 8 bits or 1 byte as the standard unit of storage. By using 6 bits, 2 were not being utilized and their capacity was being wasted. The computer manufactures, together, developed a 7 bit code and submitted it to the American National Standards Institute (ANSI) to be issued as a standard code. This ANSI issued the standard code and decried that every manufacturer shall have to implement this code on their system.
ASCII being a 7 bit code offered 128 different combinations. It had 52 binary values for alphabets, both uppercase and lowercase 10 for numerals, and 66 for special characters. It was a big improvement over the BCD code and is still being implemented on all the computer systems.
These systems have their drawbacks too. Numbers when transmitted use their ASCII values for the same, which are quite different from their numeric values. Thus, whenever arithmetic operations have to performed, the numbers have to be converted to their actual numeric values. The process of conversion is quite slow when using these codes. To eliminate this problem, IBM developed a code which assigned hexadecimal values and was very fast in arithmetic operations.
EBCDIC Code: (pronounced as eb-si-dic) is an eight bit code, known as Extended Binary Coded Decimal Interchange Code and is widely used. An 8 – bit code permits 256 unique codes, which is more than enough for our twenty-six alphabetic characters, ten decimal digits, and commonly used special symbols. Since this code can be used to handle all types of data (numeric, alphabetic, and special symbols), it is invariably used for business data processing by all types of computers mainframe as well as mini computers.
Electronic Data Processing
Data processing means transformation of data into more meaningful results for carrying out scientific, business activities. The result of data processing is called “information”. The transformation of data consist of a sequence of operations. The sequence is called “procedure”.
Input -> Processing -> Output
Data processing is a system which takes data as an input, carries out the required processing on the data and produces the information. The system is called “MANUAL” when processing is performed by human beings and “AUTOMATIC” when machines are used. When computers are used for data processing the system is called “Electronic Data Processing”.
Elements of EDP
There are five basic elements in a processing system which uses a computer for processing data. These are hardware, software, user program, procedure and personnels.
1. HARDWARE: All the physical parts which makes up a computer system called hardware i.e. all the devices or peripherals which performs the data processing operations.
2. SOFTWARE: Software consists of programs and routines whose purpose is to make the computer useable for the user. These software normally supplied by computer manufacturers or software manufacturers.
3. USER PROGRAM: A program consist of a related instructions to perform operations. A data processing job may require a number of programs.
4. PROCEDURE: The operations of data processing system requires procedure for use, in preparing data, for operating the computer and distributing the output after processing.
5. PERSONNELS: E.D.P basically needs three kinds of skilled personnels.
a) System Analyst
b) Progammer
c) Operator
a) SYSTEM ANALYST: System Analyst studies information needs and data processing requirements, design a data processing system and prepare specification.
b) PROGRAMMER: A Programmer writes a programmer on specification by System Analyst.
c) OPERATOR: An Operator is a person who operates the computer system.