Introduction to Computers Final

1 SREERAM ACADEMY (FORMERLY SREERAM COACHING POINT)

INTRODUCTION TO COMPUTERS

What is a computer?

The word computer comes from the word compute which means calculate.

Thereby, a computer is an electronic device that can perform arithmetic operations at high speed.

A computer is also called a data processor because it can store, process and retrieve data whenever desired.

Characteristics of computers

1. Automatic given a job, the computers can work automatically without human interventions. Speed computers can perform data processing, jobs very fast, usually

measured in Microseconds (10^-6), nano seconds (10^-9), pico seconds (10^-12).

Accuracy accuracy of a computer is consistently high and the degree of its accuracy depends upon its design. Computers errors caused due to incorrect input data or unreliable problems are often referred to as gigo.

Diligence computer is free from monotony, tiredness and lack of concentration. It can continuously work for hours without creating error and without grumbling.

Versatility- computer is capable of performing almost any task, if the task can be reduced to a finite series of logical steps.

Power of remembering computer can store and recall any amount of information because of its secondary storage capability. It forgets or loses certain information only when it is asked to do so.

No i.q. - a computer does only what it is programmed to do. It cannot take its own decision in this regard.

No feelings- computers are devoid of emotions. Their judgment is based on the instructions given to them in the form of programs written by us.

Computer parts There are many parts that work together to make a computer work.

Hardware - physical parts of the computer, including processor and memory chips, input/output devices, tapes, disks, modems, cable, etc.


The Central Processing Unit - the chip or chips that interpret and execute program instructions and manage the functions of input, output, and storage devices.

Computer case - contains the major components of the computer. It helps protect them.

Monitor-A display screen to provide output to the user. It is where you view the information you are working on.

Keyboard - Used to enter information into the computer and for giving commands.


Mouse - An input device operated by rolling its ball across a flat surface. The mouse is used to control the on-screen pointer by pointing and clicking, double-clicking, or dragging objects on the screen.

Touchpad - A pressure-sensitive and motion sensitive device used in place of a mouse. CD ROM drive -The drive that plays CDs and reads data that has been stored on the cd.

CD - Compact disk a type of optical storage device.

Floppy disk drive - A device that holds a removable floppy disk when in use; read/write heads read and write data to the diskette.

Hard disk - Magnetic storage device in the computer.

Ram -Random access memory - Ram is a computers temporary memory, which exists as chips on the motherboard near the CPU. It stores data or programs while they are being used and requires power.


Printer - An output device that produces a hard copy on paper. It gives information to the user in printed form.

Barcode reader - An input device that converts a pattern of printed bars into a number that a computer can read. They are often used by businesses to quickly input price and product information.

Scanner - A device that allows pictures to be placed into a computer.

Microphone - Allows the user to record sounds as input to their computer.

Speakers - Used to generate or reproduce voice, music, and other sounds.

Sound card - Connects the speakers and Microphone to the computer. Modem - The place where the computer is connected to the phone line.


Network card - A circuit board that connects the computer to the rest of the network usually using special cables.

Software - Programs that tell the computer what to do. It provides instructions that the CPU will need to carry out.

DOS - Disk operating system - This software connects the hardware with the programs you want to run.

MS-DOS: Microsoft dos (disk operating system) is a command line user interface. Ms-dos 1.0 was released in 1981 for IBM computers.

Windows - A family of operating systems developed and produced by Microsoft corp. It provides a software graphical user interface (GUI) used on IBM and compatible computers.

The CPU and RAM

Features of a CPU

1. Cache Memory

2. Clock speed: This is the speed at which the processor executes the instructions. If the clock

speed is higher, the processing speed also will be higher and such computers are faster and

efficient. Clock speed is measured in Megahertz (MHz), which means the number (in millions)

of instructions executed per second. For instance, if the clock speed is 450 MHz, it means it

can execute 450 million instructions per second. Higher the clock speed, better the

performance.

3. MMX (Multimedia Extensions): MMX is the set of instructions built onto the CPU specifically

for improving the multimedia capabilities or graphic applications. In multimedia kits, all the


audio and video facilities are available for which within the CPU multimedia features must

exist.

4. Micro processors:

It is a small processor that embodies all elements of its cousins in larger mainframe

computers: register, ALU, control unit, cache memory and so on.

These are usually manufactured by computer manufacturers such as Intel, Motorola

and so on that specialize in the manufacture of microprocessors.

There are many classes of microprocessors that are used in personal computers. They

are 8 bit, 16 bit, 32bit, 64 bit and so on. Normally, the machine of 8 bits processes 1

byte at a time and so on. If the bit pattern increases, the speed of the processor also

increases.

The electric path or line through which the data is transmitted within the computer is

called BUS.

The PC transfers the data to its input, output devices through ports that are connected

to the buses.

A port is a hardware device that allows a series of bits to be transferred to a bus from

any input device or to any output device.

Many microprocessors are quite powerful and used in scientific computers also.

Microprocessors have undergone a lot of change over the years.

5. Density:

Density refers to the number of transistors available within the CPU.

Density of the processor is very important for data processing. Millions of transistors

make up the CPU. All calculations are performed by synchronizing the transistors. If

the distance is more between two transistors, time take to process the data will also

be more.

Likewise, if the distance between two transistors is less, time taken to process the

data is less.

6. Slot: Different computers use different sockets or slots for the motherboard to fit along with

the processor. Based on the types of processors, there are two main types of slots for

connecting to the motherboard. They are socket 7 and slot 1,

7. Complementary Metal-oxide Semiconductor - The CMOS and CMOS battery allow a computer to store information even when the computer powers down. The battery provides uninterrupted power.

8. BIOS: BIOS stands for Basic Input Output System, a small chip on the motherboard that loads

the hardware settings required to load various devices like keyboards, monitors or disk drives.

Most new PCs come with flash BIOS- these BIOS can be software upgraded to support new

devices.


9. SIMM/ DIMM: SIMMs (single in-line memory modules) as a random access memory. A dual in-line memory module (DIMM) comprises a series of random access memory integrated circuits. These are used in the Computers as a random access memory. These began to replace SIMMs as the predominant type of memory module as Intel's Pentium processors began to control the market. The main difference between SIMMs and DIMMs is that SIMMs has a 32-bit data path, while DIMMs have a 64-bit data path.

10. PCI slots: Stands for "Peripheral Component Interconnect." It is a hardware bus designed by Intel and used in both PCs and Macs. Most add-on cards such as SCSI, Firewire, and USB controllers use a PCI connection. Some graphics cards use PCI, but most new graphics cards connect to the AGP slot. PCI slots are found in the back of your computer and are about 3.5" long and about 0.5" high. So before you go buy that Firewire expansion card, make sure you have at least one PCI slot available.

11. AGP slots: The Accelerated Graphics Port (often shortened to AGP) is a high-speed point-to-point channel for attaching a video card to a computer's motherboard, primarily to assist in the acceleration of 3D computer graphics

12. SCSI: Short for small computer system interface. SCSI interfaces provide for faster data transmission rates (up to 80megabytes per second) than standard serial and parallel ports. In addition, you can attach many devices to a single SCSI port, so that SCSI is really an I/O bus rather than simply an interface.

Computer Architecture plays a main role in data processing. From the computer to other peripherals,

many electronic connections are done through which data passes.

Evolution of computers

Blaise pascal invented the first mechanical adding machine in 1642. Baron gotfried invented the first calculator for multiplication in 1671. Keyboard machines originated around 1880 in the united states. Around 1880, herman hollerith came up with the punched cards that were extensively used as

the input media in india till 1970s.

Charles babbage is considered to be the father of modern digital computers He designed difference engine in 1822. He designed a fully automatic analytical engine in 1842 for performing basic arithmetic

operations.

His efforts established a number of principles that are fundamental to the design of any digital computer.


Generation in a computer talk is a step in technology. It provides a framework for the growth of computer industry.

Originally it was used to distinguish between various hardware technologies, but now it has been extended to include both hardware and software.

Till today, there are 5 computer generations.

Generation Key HW technologies

Key SW technologies

Key characteristics Some representative systems

First (1942- 1955) Vacuum tubes Machine and Assembly Languages; stored programs concept; mostly scientific application

Bulky in size; highly unreliable; limited commercial use; commercial production difficult and costly; difficult to use

ENIAC, EDVAC, EDSAC, UNIVAC I, IBM 701

Electromagnetic relay memory

Punched cards

Secondary Storage

Second (1955- 1975)

Transistors; magnetic core memory; magnetic tapes; and disks secondary storage.

Batch operating systems; high- level programming languages; scientific and commercial applications.

Faster, smaller, more reliable and easier to program than previous generation systems; commercial production was costly

Honey well 400, IBM 7030, CDC 1604, UNIVAC LARC

Third ( 1964-1975) ICs with SSI and MSI technologies; larger magnetic core memory; larger capacity magnetic disks and tapes secondary storage; mini computers

Time sharing OS; standardization of high level programming languages; unbundling of SW from HW

Faster, smaller, more reliable, easier and cheaper to produce commercially, easier to use and easier to upgrade than previous generation systems; scientific, commercial and interactive on-line applications.

IBM 360/370, PDP-8, PDP- 11, CDC 6600


Fourth (1975- 1989) ICs with VLSI technology; MICRoprocessors; semi conductor memory; larger capacity hard disks, in- built secondary; magnetic tapes and floppy disks as portable storage media; personal computers; high speed NWs

OS for PCs; GUI; Multiple windows on a single terminal screen; UNIX OS, C Programming language; PC- based applications; Network based applications

Small, affordable, reliable and easy to use PCs, more powerful and reliable mainframe systems; general purpose machines; easier to produce commercially.

IBM PC and its clones, Apple II, TRS- 80, CRAY

Fifth Generation (1989- present)

ICs with VLSI technology, larger capacity unit hard disks, optical disks as portable read- only storage media; notebook computers; powerful desktop PCs and work stations; very powerful mainframes, Internet

WWW, Multimedia applications; Internet based applications

Portable computers; more powerful; cheaper; reliable; and easier to use; desktop machines; very powerful mainframes; very high uptime due to hot pluggable components; general purpose machines; easier to produce commercially.

IBM notebooks, Pentium PCs, SUN workstations, IBM SP/2, etc

Size of computers

Super computers Most powerful, most expensive and fastest. Used for defense, aircraft, computer generated weather report, petroleum industry, etc. Speed is measured in nano seconds. Processors perform task simultaneously and can connect to 10,000 terminals at a time.

Main frame computers 1. Power, cheaper in cost and fast computers.

2. Airline booking, railway reservation and network banking.

3.the speed is measured in megaflops.

4. Multiprogramming- capability to SWitch between programs.

5. Can support upto 10,000 terminals at a time.

Micro computers 1. Fully ledged computer system 2. Uses MICRo processor as CPU 3. Runs on various os dos, windows, etc. 4. Personal computers for the general purpose of the users.


Mini computers 1. Performs the same activities of mainframe on a smaller scale. 2. Caters to multiple users accessing at the same time. 3. Serves as information processors in small to medium sized firms or processors in computer

network for large firms. Electronic devices used in various generations

Concepts

Chipset- many technologies, met on mother board are glued together via these controllers which we call the chipset.

Data flow on the mother board the CPU is the brain of the pc. The buses are the nervous system of Mother board. They connect CPU to all other components. The buses are pcs express ways, which transmits data between different components.

CPU it is a processor because it moves and calculates data. It is central because it is centre of pc data processing. It is an unit because its a chip which contains millions of transistors.

Clock speed- It is the speed at which the processor executes instructions. Measured in HZ.

Clock frequency- There is a small crystal on mother board; which continually ticks to the CPU at a steady number of clock ticks/ second. At each clock tick something happens in the CPU. Thus more ticks/ second more data are processed.

BIOS - Small chip on the mother board which loads the hardware settings required to load various input and output devices. Most PCs come with flash bios that can be software upgraded to support new devices.

CMOS - To store date, time and system set parameters. These are loaded every time the computer is started. A small lithium iron battery powers the CMOS and BIOS in the mother board.

Bits - Computer remembers everything in bits. They think in bits. Binary helps us understand bits. 1 bit/second means it can change 2v to 5v and 5v to 2v on one second. A computer can change volts very fast.


CISC and RISC - The first CPUs had so called CISC (complex instruction set computer). This means computer can understand many complex instructions. RISC are brief and the same length and process, much faster than CISC.

Mother board - The mother board or (PCB) is the main circuit board on the computer. Directs as a direct channel for the various components to communicate. Components:

Processor slots Expansion slots Ports

Expansion Slots Common expansion cards:

Graphics card (for connecting to a monitor) Network card (for transmitting data over a network) Sound card (for connecting to a Microphone and speakers)

Most PCs offer 4-8 expansion slots. There are several different types of expansion slot:

ISA: older technology, for modems and slow devices PCI: for graphics, sound, video, modem or network cards

AGP: for graphics cards Basic organization of a computer

Input unit

An input unit perform the following functions:

1. It accepts (reads) instructions from outside world.


2. It converts these data/ instructions in computer acceptable form.

3. It supplies the converted data/ instructions to the computer for further processing. Output unit

1. It accepts the results produced by the computer, which are in coded form and hence cannot be understood by us.

2. It converts these coded results to human acceptable form.

3. It supplies the converted results to outside world. Two types of storage:- Primary storage

1. Used to hold running program instructions.

2. Fast in operation

3. Small capacity

4. Expensive

5. Volatile (loses data on power cut) Storage unit

1. Data and instructions are required for processing from the input devices.

2. Intermediate results of processing.

3. Final results of processing before they are released to an output device. Secondary storage

1. Used to hold stored program instructions.

2. Slower than primary storage

3.large capacity

4. Lot cheaper than primary storage

5. Retains data even without power. Primary Memory Secondary Memory

Primary memory is volatile with an exception of ROM.

Secondary memory is non volatile.

It is costlier It is relatively cheaper.

It is close to CPU It is relatively far from CPU

Capacity is low Capacity is high

Processing is faster Processing is relatively slower

It is in chip form It is in tape or disk form

Primary memory is not portable Secondary memory is portable

Primary memory is not to be formatted by the user.

It is to be formatted

Data cannot be saved in primary memory Essentially used with an intention of saving

Primary memory is in direct access Secondary memory will be of direct/ sequential access.


ALU

ALU is the place where actual execution of instructions takes place during processing operation.

Control unit

Control unit controls and coordinates the operations of all other components of the computer system.

Registers

Special memory units called registers are used to hold information on a temporary basis as the instructions are interpreted and executed by CPU.

Registers are part of the CPU ( not the main memory).

The amount of the data that it can hold is measured in bits. Storage evaluation criteria

Property Desirable Primary Storage

Secondary Storage

Storage capacity

Large Small Large

Access time Fast Access Time

Fast Slow

Cost per bit of storage

Low cost per bit

High Low

Volatility Non volatile

Volatile Non volatile

Access Random Access

Random access

Sequential access

RAM- Random Access Memory

Primary storage of a computer is referred to as ram.

Ram chips are volatile memory.

A computers MB is designed in a manner that the memory capacity can be enhanced by adding more memory chips.

The additional ram chips which plug into special sockets on the MB are known as single- in- line memory modules (SIMM).

ROM- Read Only Memory

ROM a non volatile memory chip.

Data stored in ROM can only be read and used they cannot be changed.

ROMs are mainly used to store programs and data which do not change and are frequently used. Eg- system boot program.


Types of ROM

Manufacturer- programmed ROM: data is burnt by the manufacturer on the electronic equipment under which it is used.

Programmable ROM store only read only.

Erasable pROM- user can erase programs and the ROM can be reprogrammed.

Ultraviolet epROM

Electrically epROM (flash memory)

Cache (pronounced as cash)

Used to cover up memory- processor speed mismatch

Library- example

To understand the basic idea behind a cache system, let's start with a super-simple example that uses a librarian to demonstrate caching concepts. Let's imagine a librarian behind his desk. He is there to give you the books you ask for. For the sake of simplicity, let's say you can't get the books yourself -- you have to ask the librarian for any book you want to read, and he fetches it for you from a set of stacks in a storeroom (the library of congress in Washington, D.C., is set up this way). First, let's start with a librarian without cache.

The first customer arrives. He asks for the book Alchemist. The librarian goes into the storeroom, gets the book, returns to the counter and gives the book to the customer. Later, the client comes back to return the book. The librarian takes the book and returns it to the storeroom. He then returns to his counter waiting for another customer. Let's say the next customer asks for Alchemist (you saw it coming...). The librarian then has to return to the storeroom to get the book he recently handled and give it to the client. Under this model, the librarian has to make a complete round trip to fetch every book -- even very popular ones that are requested frequently. Is there a way to improve the performance of the librarian? Yes, there's a way -- we can put a cache on the librarian. In the next section, we'll look at this same example but this time, the librarian will use a caching system. Let's give the librarian a backpack into which he will be able to store 10 books (in computer terms, the librarian now has a 10-book cache). In this backpack, he will put the books the clients return to him, up to a maximum of 10. Let's use the prior example, but now with our new-and-improved caching librarian. The day starts. The backpack of the librarian is empty. Our first client arrives and asks for Alchemist. No magic here -- the librarian has to go to the storeroom to get the book. He gives it to the client. Later, the client returns and gives the book back to the librarian. Instead of returning to the storeroom to return the book, the librarian puts the book in his backpack and stands there (he checks first to see if the bag is full -- more on that later). Another client arrives and asks for Alchemist. Before going to the storeroom, the librarian checks to see if this title is in his backpack. He finds it! All he has to do is take the book from the backpack and give it to the client. There's no journey into the storeroom, so the client is served more efficiently. What if the client asked for a title not in the cache (the backpack)? In this case, the librarian is less efficient with a cache than without one, because the librarian takes the time to look for the book in his backpack first. One of the challenges of cache design is to


minimize the impact of cache searches, and modern hardware has reduced this time delay to practically zero. Even in our simple librarian example, the latency time (the waiting time) of searching the cache is so small compared to the time to walk back to the storeroom that it is irrelevant. The cache is small (10 books), and the time it takes to notice a miss is only a tiny fraction of the time that a journey to the storeroom takes.

Limitations of primary storage

Volatile

Expensive and so limited capacity Secondary storage

Cost per bit is low, hence overcomes the disadvantages of primary storage.

Operating speed is slower than primary storage

Used to store data on a permanent basis.

Also known as auxiliary memory.

Sequential access storage devices

1. Data can only be retrieved in the same sequence in which it is stored.

2. Access time varies according to the storage location of the information being processed.

Secondary Storage

Sequential access

device

Magnetic tape

Direct Access Devices

Magnetic disks

Floppy Disks

Hard disks

Winchester Disk

Disk Pack

Zip disk

Optical disks

DVD

CD- RW

WORM Disks

CD ROM

Memory storage devices

Memory Card

Flash drive


3. Suitable for sequential processing applications where most, if not all of the data records needs to be processed one after the other.

4. Example- magnetic tape. Direct access storage devices

Devices where any storage location may be selected and accessed at random.

Permits access to individual information in a more direct or immediate manner.

Equal access time from any storage location.

Suitable for online booking systems, online banking systems, etc.

Magnetic, optical disks are examples. Magnetic tape basics

Commonly used sequential access storage device.

Physically, the tape medium is a plastic ribbon which is usually 1.2 inch, 1.4 inch wide and 50 to 2400 ft long.

Plastic ribbon is coated with magnetizable recording material such as iron oxide or chROMium dioxide.

Data are recorded in the form of tiny invisible magnetized and non magnetized spots (0 s and 1s ) on the coated surface.

Tape ribbon is stored in reels or cassettes. Advantages of magnetic tapes

Storage capacity is virtually unlimited because as many tapes as required can be used for storing very large data.

Cost per bit is very low.

Tapes can be erased and used many times.

Compact and light in weight.

Easy to handle and store Limitations

Not suitable for data that has to be accessed randomly.

Has to be stored in a dust free environment as dust could cause reading problems.

Stored in properly controlled temperature and humidity levels.

Tape ribbon may get twisted due to warping, resulting in loss of stored data.

Should be properly labeled. Magnetic disk

Commonly used direct access storage device.

Physically, its a thin circular plate made of metal or plastic that is usually coated on both sides with a magnetizable recording material such as iron oxide.

Data are recorded by tiny invisible magnetized and non- magnetized spots on the coated surface of the disk.

Disk is stored on a protected envelope.


Disk organization

Disk formatting

Process of preparing a new disk by the computer system in which the disk is to be used. Os- formatting - creates a fat that is a table with the sector and track locations of data. leaves sufficient space for fat to grow scans and marks bad sectors. Disk drive is the unit used reading/ writing of data on / from a disk.

Types of magnetic disks Floppy disks

Round piece of flexible plastic cards, coated with magnetic oxide.

So called because they are made of flexible plastic plates which can bend.

Also known as floppies or diskettes.

Plastic disk is encased in a plastic jacket that gives handling protection to the disk surface. Hard disks

Round, flat piece of rigid metal (frequently Aluminum) disks coated with magnetic oxide.

Come in many sizes

Depending on how theyre packed, they can be 3 types.

Zip disks, winchester disks and disk packs.

Primary online secondary storage for most devices. Advantages of magnetic disks

Direct access of data

Can be used by multiple users through a shared device.

Used for online and off-line storage of data.

Low cost

Less storage space.

Large amounts of data

Optical Disks uses laser beam technology for reading/ writing data

CD- ROM

Stands for compact disk read only memory


Information stored cannot be altered

Pre stamped and pre recorded by the supplier by a process called mastering.

Holds a storage capacity of about 650mb

Disadvantages

Stored in dust free environment.

Tapes are must cheaper.

Disk crash could lead to huge loss.

Security is an issue. Worm disks/ CD-R (CD Recordable)

Stands for write once, read many.

Data can be written only once on them, but can be read many times.

Allow users to create their own cd- ROM disks by using a cd- r drive that can be attached to a computer as a regular peripheral device.

Data can be recorded in multiple recording sessions.

Used for permanent archiving. Eg- banks. CD read/ write (CD-RW)

Same as cd-r and same storage capacity.

Can be erased and written afresh. DVD- digital video disk

Looks like cd- ROM but has a capacity of 4.5 gb- 8.5 gb.

Designed primarily to store and distribute movies. Advantages of optical disks

Cost per bit is low because of their enormous storage capacity.

Extended data storage life.

No mechanical read/ write heads. Hence more reliable.

Danger of data getting erased is removed.

It is largely read only. Data once stored cannot be erased. Flash drive (pen drive) memory card Input/ output devices

1. Provides means of communication between a computer and outer world.

2. Also known as peripheral devices because they surround the CPU and memory of a computer system

3. Input devices are used to enter data from the outside world into primary storage.

4. Output devices supply results of processing from primary storage to others.


Commonly used input devices

Keyboard : allow data by pressing a set of keys. Qwerty keyboard is most popular.

Mouse

Track ball (similar to mouse with a ball, used in laptops)

Joy stick- used for video games, flight simulators, for controlling industrial robots.

Electronic pen

Touch screen

Most simple and easiest to learn.

Enables users to choose from various options by simply touching with their finger the desired icon or menu item displayed on the screen.

Most preferred human computer interface used in information kiosks like atm.

Optical character recognition devices

Scanner equipped with a character recognition software that converts the bit map images to equivalent ASCII codes.

Enables word processing of input text also requires less storage for storing the document as text rather than as an image.

OCR is extremely complex because it is difficult to make a computer recognize an unlimited number of typefaces and fonts.

2 types :OCR a ( American )and OCR - b (European)

Optical mark reader

Scanner capable of recognizing pre- specified type of mark by pencil or pen.

Very useful for grading tests with objective type questions, or for any input data that is of choice or selection nature.

Technique used for recognition of marks involves focusing a light on the page being scanned and detecting the reflected light pattern from the marks.

Bar code reader

Scanner used for reading bar- coded data.

Bar codes represent alpha- numeric data by a combination of adjacent vertical lines by varying their width and spacing between them.

Scanner uses laser- beam to stroke across pattern of bar code. Different patterns of bar reflect the beam in different ways sensed by a light sensitive detector.

Universal Product Code (UPC) is the most widely known bar code system. Magnetic ink character recognition (MICR)

MICR is used by banking industry for faster processing of large volumes of cheque.

Banks identification code (name, branch, etc), a/c number, cheque number and pre printed (encoded) using characters from a special character set on all cheques.

Special ink is used that contains magnetizable particles of iron oxide.

MICR sorts data on cheques and sorts them for distribution to other banks or for further processing.

MICR 0 to 9 and 4 special characters


Digitizer

For converting pictures, maps and drawings in digital form for storage in computers.

Commonly used by architects to design cars, buildings, robots, mechanical parts, etc.

Digitizing maps in paper form. Image scanner

Input device that translates paper documents into an electronic format for storage in a computer.

Electronic format for a stored image is in bit map representation.

Stored image can be altered or manipulated with image processing software Types of output

Hard copy output

Soft copy output Monitors

Monitors are the most popular output devices used for producing soft copy output.

Display the output on a screen

Monitor associated with a keyboard is called VDT (video display terminal). It is the most popular I/O device.

A monitor is a peripheral device which displays computer output on a screen.

Screen output is referred to as soft copy.

Types of monitors: Cathode-ray tube (crt) Liquid crystal display (lcd or flat-panel)

Printers for hard copy output

A printer is a peripheral device that produces a physical copy or hard copy of the computers output.

Types of printers Impact Printers

1) Impact printers utilize striking device to transfer ink from an inked ribbon onto the paper being printed to form images or characters.

2) The characters are formed by whole alpha numeric images produced by a process known as full character or formed character printer.

3) The characters are also formed by a dot matrix method which arranges a series of dots to assume the shape of each character being printed.

4) Impact printing can be serial printing or line printing. Non Impact Printers

1) A non- impact printer forms characters by chemical or electronic means. 2) They are fast in operation and printing a page.


3) Three types of non impact printers are significant; they are thermal printers, inkjet printers and laser printers.

4) Non- impact printers produces very high quality prints from a wide selection of character fonts.

Daisy Wheel Printers

1) A wheel with each possible character strikes a ribbon with the desired character facing. 2) The paper, making a mark according to the character engraved on the wheel. 3) They were the first printers available and are no longer in common use. 4) Totally obsolete. 5) Very slow 6) Could only produce the characters engraved on their wheels.

Dot Matrix Printers

1) A Pin strikes a ribbon, causing a mark on the paper. 2) A series of pins can create characters by striking the ribbon with the pins in the shape of the

desired character. 3) Some types of printing jobs require press- through copies, requiring some form of impact. 4) This is the only form of printer that still uses the impact method. 5) Impact printers are slow by nature and noisy. 6) They also have a much harder time drawing graphics, produce very low quality output. Laser Printer 1) A Laser printer is a popular type of personal computer printer that uses a non- impact (keys

dont strike the paper), photocopier technology. 2) When a document is sent to the printer, a laser beam draws the document on a selenium-

coated drum using electrical charges. 3) After the drum is charged, it is rolled in toner, a dry powder type of ink. The toner adheres to

the charged image on the drum. The toner is transferred onto a piece of paper and fused to the paper with heat and pressure.

4) After the document is printed, the electrical charge is removed from the drum and the excess toner is collected. Most laser printers print only in monochrome. A color laser printer is up to 10 times more expensive than a monochrome laser printer.

5) IBM introduced the first printer in 1975 for use with its main frame computers. In 1984, Hewlett-Packard revolutionized laser printing technology with its first laser Jet, a compact, faster and reliable printer that personal computer users could afford.

6) Since then laser printers have decreased further in price and increased in quality. Inkjet Printers

1) The Laser printer is different form an inkjet printer in a number of ways. The toner in a laser printer is dry. In an Inkjet. It is wet.

2) Over time, an inkjet printer is about ten times more expensive to operate than a laser printer because ink needs replenishing more frequently.


3) The printed paper from an inkjet printer will smear if wet, but a laser printed document will not. Both types of printer operate quietly and allow fonts to be added by using font cartridges or installing soft fonts.

4) If the printing need is minimal, an inkjet printer is sufficient. But if printing volume is high, a laser printer is preferable.

Line printers

1) A line printer operates at much higher speeds and prints what appears to be a full line at a time.

2) Line printers are only used where high speed and volume is necessary and where quality is the lesser requirement. Two types of line printers include:

Chain Printers

1) It has a chain that revolves at a constant speed in a horizontal axis. 2) The complete chain has a complement of 48 characters (numbers, alphabets, special symbols)

cast on 5 times. 3) It is confronted by a set of as many hammers as the number of print position (say 48 X 5= 160) 4) These hammers are magnetically controlled. 5) The continuous stationery and ribbon are inter- posted between a segment of the chain and

the set of hammers. 6) When a required character on the chain faces its print position, the corresponding hammer is

actuated. Drum Printers

1) These printers use a solid cylinder there are as many rows on it as the number of print positions.

2) Each band has cast on it the complement of 48 numerals, alphabets and special characters. 3) The Drum rotates at a constant speed confronted by a set of as many hammers as the

number of bands with the inked ribbon and continuous stationery inter- post. 4) In one rotation of the drum there would be appropriate strikes by the set of the hammers. 5) In the first strike As are printed in the appropriate print positions followed by

B,C.Z,0,19 and special symbols one by one. Thermal Printers

1) A printer that uses heat to transfer an impression onto paper. There are two kinds of thermal printers:

Thermal wax transfer: a printer that adheres a wax-based ink onto paper. 2) A thermal print head melts wax-based ink from the transfer ribbon onto the paper. When

cool, the wax is permanent. This type of thermal printer uses an equivalent panel of ink for each page to be printed, no matter if a full page or only one line of print is transferred.

3) Monochrome printers have a black page for each page to be printed, while color printers have either three (CMY) or four (CMYK) colored panels for each page. Unlike thermal dye transfer printers, also called dye sublimation printers, these printers print images as dots, which means that images must be dithered first.


4) As a result, images are not quite photo-realistic, although they are very good. The big advantages of these printers over thermal dye transfer printers are that they don't require special paper and they are faster.

5) Direct thermal: a printer that prints the image by burning dots onto coated paper when the paper passes over a line of heating elements. Early fax machines used direct thermal printing.

Plotter

A plotter is a printer that uses a pen that moves over a large revolving sheet of paper.

It is used in engineering, drafting, map making, and seismology. Audio output: sound cards and speakers

Audio output is the ability of the computer to output sound.

Two components are needed:

sound card plays contents of digitized recordings

speakers attach to sound card Audio input: speech recognition

Speech recognition is a type of input in which the computer recognizes words spoken into a microphone.

Special software and a microphone are required.

Latest technology uses continuous speech recognition where the user does not have to pause between words.

Microfiche

The major advantages of Microfiche include storage in a small space, stability of the format, and no special knowledge needed to read it. As long as a Microfiche machine is available to magnify the print to readable size, anyone who can read the language can read a Microfiche. Because of its small size, Microfiche can be archived in storage cabinets, saving floor space. Thousands of government documents are archived on Microfiche for this very reason.

Microfiche, like microfilm, is also a stable archival format. When kept in a temperature-controlled environment, it is rated to last 500 years a crucial advantage in saving cultural documents

Software

Hardware refers to physical devices of a computer system.

Software refers to collection of programs.

Program is a sequence of instructions written in a language that can be understood by the computer.

Software package is a group of programs that solve a specific program or perform a specific type of job.

System software- extend the processing capability

Help hw components work together and provide support for the development and execution of system SW.

Programs included in a system SW are called system programs.

Examples : operating systems, programming language, translators, utility programs


Application software

Solve a specific problem or to do a specific task.

Programs included are called application programs.

Examples- word processing, tally, etc Ways of acquiring SW

Buy pre-written SW

Order customized SW

Develop customized SW

Downloading public domain SW

Firmware

Firmware is SW substituted for HW and stored in ROM.

Firmware technology has enabled production of various types of smart machines having microprocessor chips with embedded SW.

Middleware

Basic idea is to have a separate SW layer to:

Act as glue between client and server part of application.

Provide programming abstraction

Mask heterogeneity of underlying HW, NW and OS.

Encourage 3 tier SW architecture against 2 tier. Virtual Memory and Main Memory

Basis Virtual Memory Main Memory

Meaning Virtual memory is a technique that allows the execution of a process, even though the logical address space requirement of the process is greater than the physically available main memory.

Main Memory is a part of the computer hardware which stores program and data that are active in use.


Storage Capacity Virtual memory extends primary memory by treating disk storage as a logical extension of the main memory, thus increasing the storage capacity.

Main Memory has limited storage capacity.

Memory Utilization Virtual Memory helps in efficient main memory utilization. More programs can be run at the same time.

Main Memory can run a single program at a time hence CPU is not fully utilized.

RAM and ROM

Basis RAM ROM

Used for RAM is used as main computer memory.

ROM is used for storing micro programs and control instructions that allows special operations to be performed by the machine.

Volatility RAM is volatile or temporary memory

ROM is non volatile or permanent memory

Users Programmers and machine both use RAM

Only machines use ROM

Things stored Data and programs can be stored in RAM either through input devices or through auxiliary storage devices

ROM does not allow data to be stored instead they are written by its manufacture once for all.

Reading and Re-writing The data and instructions written on the RAM can be read and re-written.

Instructions written on ROM can be read but cannot be re-written.

Power interruptions Power interruptions destroy RAM contents or data stored.

Power interruptions do not destroy the contents of ROM.

Bubble Memory Is composed of small magnetic domains (bubbles) formed on a thin single- crystal film of

synthetic gamel. These magnetic bubbles, which are actually magnetically, charged cylinders, only few

thousandths of a centimeter in size, can be moved across the garnet film by electric charges. The presence or

absence of a bubble can be used to indicate whether a bit is on or off.

Since the data stored in a bubble memory is retained when power to the memory is turned off, it can be used

for auxiliary storage. Bubble memory has high potential because of its low production costs and its direct

access capabilities, thus it may become widely employed as a main memory technology. Since its small, light

weight and does not use much power, bubble memory is finding a great deal of use an auxiliary storage in

portable computers. It is expected that as more portable computers are developed, bubble memory will

become more widely used.


Inter block Gap (IBG):

1) A block is a unit of transfer which means from the tape to the CPU, bunches of characters are

carried.

2) In order the blocks are read, the tape is expected to run at a constant speed.

3) While a block is picked for processing, it involves consumption of time. During that time, the

tape is running at a constant speed. If the next block is juxtaposed (beneath the next block)

here is a possibility of skipping the block.

4) In order to prevent this, a gap is necessary between adjacent blocks. This block is called IBG.

5) However, to minimize the wastage, due to empty run, a combination of retardation and

acceleration are carried out.

Utilities and libraries

Utility programs are also known as service programs. They perform tasks that are common to all

data processing jobs. These programs are stored in a DASD and called by the OS when required.

Examples of Utility program are:-

Sorting records in a particular sequence

Merging several files into a single file

Editing the data or text

Copying files from disk to tape or disk to floppy.

Printing

Comparing two sets of data.

Libraries are collections of frequently used programs. These programs are usually small in size

and not fully fledged programs. They are subordinate to the main programs and called sub-

routines.

A sub- routine may be defined as a sub set of instructions that appears over and again in the

program of is employed in several programs. E.g. computation of square root, translating

amounts in figures to amount in words, printing headers, etc.

Diagnostic routines

The programs held in hand in finding out errors in applications programs and assist in debugging.

They help in executing the program lines step by step, trace the logic and trap errors.

Spooling software

1. The purpose of spooling software is to compensate for the speed differences between the computer and its peripheral devices.

2. Spooling software is usually encountered in large system and network computing environments. For instance, during the time it takes to type in or print out all the words on this page, the computer could begin and finish processing dozens of programs.


3. The computer would be horribly bottlenecked if it had to wait for slow input and output devices before it could resume processing. It just does not make sense for a large computer, which may be worth lacs of rupees, to spend any time sitting idle because main memory is full of processed but unprinted jobs and the printer attached to the system cannot move fast enough.

4. To preclude the computer from being slowed down by input and output devices, many computer systems employ spooling software. These programs take the results of computer programs and move them from primary memory to disk. The area on the disk where the program results are sent is commonly called the output spooling area.

5. Thus, the output device can be left to interact primarily with the disk unit, not the CPU. Spooling utilities can also be used on the input side, so that programs and data to be processed are temporarily stored in an input spooling area on disk.

6. Assume for example that a floppy disc, a line printer and a disk are used in a spooling operation on a computer system to process the pay-roll and prepare invoices by loading both programs into the main memory. While the line printer is printing an invoice line, the processor switches to the pay roll application and transfers input data from floppy disc to magnetic disk.

7. Afterwards the processor reverts back to the invoice application. As the printer is being used for printing invoices, pay roll application will be executed and output data would be recorded on the Magnetic disk for later conversion when the printer becomes available. As a result, the CPU can give the output at the maximum speed, while several relatively slow input and output unit cooperate simultaneously to process it.

Translators

1. These are also known as translating programs. They transform the lines of instructions written

by the programmer into codes that can be read by the machine.

2. Translators are the common reference for the different software such as interpreters,

assemblers, compilers, etc.

3. Translators refer also to software that can convert statements from one language to those in

another. The term language processor is also used for meaning translator.

Text Editors

These are programs that allow text to be created as a file and modified. These are most useful to

professional programmers who have to create new programs or modify the earlier ones. These

programs allow the facility of cutting and pasting text blocks as also other features such as spell

check, syntax verification and so on.


Language Classification

A programming language that is once removed from a computer's machine language. Machine languages consist entirely of numbers and are almost impossible for humans to read and write. Assembly languages have the same structure and set of commands as machine languages, but they enable a programmer to use names instead of numbers.

Each type of CPU has its own machine language and assembly language, so an assembly language program written for one type of CPU won't run on another. In the early days of programming, all programs were written in assembly language. Now, most programs are written in a high-level language such as FORTRAN or C. Programmers still use assembly language when speed is essential or when they need to perform an operation that isn't possible in a high-level language.

A human language. For example, English, French, and Chinese are natural languages. Computer languages, such as FORTRAN and C, are not. Probably the single most challenging problem in computer science is to develop computers that can understand natural languages. So far, the complete solution to this problem has proved elusive, although a great deal of progress has been made. Fourth-generation languages are the programming languages closest to natural languages.

Compiler and Interpreter

Basis Compiler Interpreter

Functioning It scans the whole program at a time and list out the error if any.

It scans the program line by line and stops scanning if any error occurs.

Conversion of source Whole of the source code is converted to object code at a time by a compiler.

Source programs are converted line by line into object by interpreter and immediately executed.

Source code requirement No need of source code after combination.

Source code required for every execution.

Speed Execution is faster Execution is slower

Object code generation The object code is generated when program is free.

Interpreter generates object code for the line immediately if it is error free.


Decision Support System (DSS)

A DSS is an information processing system frequently used by accountants, managers and auditors to

assist them in the decision making process. DSS of computer systems that combines data analytical

tools and user friendly software to support semi structured and un-structured decision making. They

are generally used at the management level of an organizational level for decision making. Semi

Structured and un-structured situations are non- repetitive problems for which no standard solutions

exist and also t hey doesnt have well defined processing rules. Flexibility is the vital key in developing

decision making system for semi- structured problems, since different managers are likely to

approach the process differently. Advances in hardware technologies, interactive computing design,

graphics capabilities and programming languages contributed to this evolution.

A DSS has 4 basic components:-

1. The User: The user of a DSS is generally a manager with an unstructured or semi

structured problem to solve A manager may be at any level of authority in the

organization. They do not need a computer background to use the DSS for solving a

problem because a special planning language performs the communication functions

within the DSS.

2. Databases: There is more than one database included in DSS. These databases contain

both routine and non routine data from both internal and external sources. The data

from external sources may contain or relate to the operating environment surrounding

the organization like economical condition, industry competitions, etc. Database may

also capture data from other sub systems such as marketing, production and

personnel.

3. Model base: Data manipulations and computations with data provided to be DSS by

the user and the database is done by the model base. It includes mathematical model

and analytical techniques to process and manipulate the database. The model base

may dictate the type of data included in the database and the type of data provided by

the users. Analysis provided by the routines in the model base is the key to support the

users decision.

4. Planning languages: Two types of planning languages commonly used in DSS are:

General purpose planning language: They allow the user to perform many routine

tasks like data retrieval analyzing etc. Example- Language in most electronic spread

sheets.

Special purpose planning language: Their task is limited to performance of pre

determined / preprogrammed instructions. They can do their jobs better. Example-

SAS, SPSS.


Expert systems

Expert systems are systems that allow a person not having specialized knowledge or experience to

make decisions, comparable to that of an expert. Expert systems contain the knowledge used by an

expert in a specific field in the form of If/ then rules and an engine capable of drawing inference

from this knowledge base.

Components of Expert system are:-

1. Knowledge base: it is the computer equivalent to all the knowledge and insight that an expert

or a group of expert develop through years of experience in their field.

2. Inference Engine: it is the basic logic and reasoning mechanism that stimulates the expert

logic process and deliver advice. It uses data obtained from both the knowledge base and user

to make associations and inferences from its conclusions and recommend a course of action.

3. User interface: This part or program allows the user to design, create, update, use and

communicate with the expert system.

4. Explanation facility: This facility provides the user with an explanation of the logic the expert

system used to arrive at its conclusions.

5. Knowledge acquisition facility: Building a knowledge base referred to as knowledge

engineering involves both a human expert and a knowledge engineer. The knowledge

engineer is responsible for extracting an individuals expertise and using the knowledge

acquisition facility to enter it into the knowledge base.

Advantages:

1. It is a cost effective alternative to human experts.

2. It can outperform a single expert as it is a representative of numerous experts.

3. It can produce better quality decision and more consistent decisions as they are not

distracted, over worked or stressed out.

4. Expert system assist users in identifying potential decision making problems, which increases

the probability that sound decisions, will be made.

5. They can increase productivity.

6. They preserve the expertise of an expert leaving the organization.

Object Oriented Concepts

In old style programming, you had:

data, which was completely passive

functions, which could manipulate any data

An object contains both data and methods that manipulate that data


An object is active, not passive; it does things

An object is responsible for its own data

But: it can expose that data to other objects

An object contains both data and methods that manipulate that data

The data represent the state of the object

Data can also describe the relationships between this object and other objects

Example: A Checking Account might have

A balance (the internal state of the account)

An owner (some object representing a person

You could (in a game, for example) create an object representing a rabbit

It would have data:

How hungry it is

How frightened it is

Where it is

And methods:

eat, hide, run, dig

Every object belongs to (is an instance of) a class

An object may have fields, or variables -The class describes those fields

An object may have methods -The class describes those methods

A class is like a template, or cookie cutter

An Abstract Data Type (ADT) bundles together:

some data, representing an object or "thing"

the operations on that data

Example: a Checking Account, with operations deposit, withdraw, get Balance, etc.

Classes enforce this bundling together


Classes are arranged in a treelike structure called a hierarchy

The class at the root is named Object

Every class, except Object, has a super class

A class may have several ancestors, up to Object

When you define a class, you specify its super class

If you dont specify a super class, Object is assumed

Every class may have one or more subclasses.

Inheritance: Inheritance is the property whereby one class extends another class by including

additional methods and/or variables. The original class is called the super class of the extending class,

and the extending class is called the subclass of the class that is extended. Since a subclass contains all

of the data and methods of the super class plus additional resources, it is more specific. Conversely,

since the super class lacks some of the resources of the subclass, it is more general or abstract, than its

subclasses.

Encapsulation means as much as shielding. Each object-oriented object has a shield around it. Objects

can't 'see' each other. They can exchange things though, as if they are interconnected through a hatch.

It separates the external aspects of an object from the internal implementation details of the object,

which are hidden from other objects. The object encapsulates both data and the logical procedures

required to manipulate the data.

Introduction to Computers Final

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