I Bcom(CA) _ 2021 Notes
Q: What is Computer? |
Ans: Computer is an electronic device which can transforms data. Data can be anything like marks obtained in various subjects. It can also be name, age, sex, weight, height, etc. of all the students in class.
Computer can be defined in terms of its functions. It can i) accept data ii) store data, iii) process data as desired, and iv) retrieve the stored data as and when required and v) print the result in desired format.
Q: What are characteristic of computer? |
Ans:
1. Speed: - As we know computer can work very fast. It takes only few seconds for calculations that we take hours to complete. 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).
2. Accuracy: - The degree of accuracy of computer is very high and every calculation is performed with the same accuracy. The accuracy level is determined on the basis of design of computer. The errors in computer are due to human and inaccurate data.
3. 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.
4. Versatility: - It means the capacity to perform completely different type of work. We can use computer to prepare payroll slips. Next moment we may use it for inventory management or to prepare electric bills.
5. 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 we to decide what we want to do and in what sequence. So a computer cannot take its own decision as you can.
6. 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.
Q) What are Basic Computer Operations? (OR) Describe the logical organization of digital computers.(OR) Draw a Block Diagram of Computer. |
Ans: - A computer can perform five major operations or functions. These are 1) it accepts data or instructions by way of input, 2) it stores data, 3) it can process data as required by the user, 4) it gives results in the form of output, and 5) it controls all operations inside a computer.
Q: What is Computer? |
Ans: Computer is an electronic device which can transforms data. Data can be anything like marks obtained in various subjects. It can also be name, age, sex, weight, height, etc. of all the students in class.
Computer can be defined in terms of its functions. It can i) accept data ii) store data, iii) process data as desired, and iv) retrieve the stored data as and when required and v) print the result in desired format.
Q: What are characteristic of computer? |
Ans:
1. Speed: - As we know computer can work very fast. It takes only few seconds for calculations that we take hours to complete. 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).
2. Accuracy: - The degree of accuracy of computer is very high and every calculation is performed with the same accuracy. The accuracy level is determined on the basis of design of computer. The errors in computer are due to human and inaccurate data.
3. 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.
4. Versatility: - It means the capacity to perform completely different type of work. We can use computer to prepare payroll slips. Next moment we may use it for inventory management or to prepare electric bills.
5. 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 we to decide what we want to do and in what sequence. So a computer cannot take its own decision as you can.
6. 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.
Q) What are Basic Computer Operations? (OR) Describe the logical organization of digital computers.(OR) Draw a Block Diagram of Computer. |
Ans: - A computer can perform five major operations or functions. These are 1) it accepts data or instructions by way of input, 2) it stores data, 3) it can process data as required by the user, 4) it gives results in the form of output, and 5) it controls all operations inside a computer.
1. Input Unit: This is the process of entering data and programs in to the computer system. These devices translate data from human understandable form into electronic impulses, which are understood by the computer. The most common input device is the keyboard, mouse, joystick, scanner, digitizer etc.,
2. Central Processing Unit (CPU):
Once the data is accepted it is fed into central processing unit before the output is generated as data has to be processed, which is done by CPU. This unit of the computer is the brain of computer system, which does all the processing, calculations, problem solving and controls all other functions of all other elements of the computer. The CPU consists of the following three distinct units namely
(i) Memory Unit
(ii) The Control Unit
(iii) The Arithmetic and Logic Unit
(i)Memory Unit:
This is the unit where the data and results are stored. This unit consists of cells which are capable to store unit of information. These cells can be accessed as they are numbered sequentially, which are called addresses. This memory unit is usually referred as primary storage section.
(ii) The Control Unit:
This is that unit of CPU, which coordinates all the activities of each and every element of computer. It decodes the instructions given by various users and it sends commands and signals that determine the sequence of various instructions. Though this unit does not process data but it acts as the central system for data manipulation, as it controls the flow of data to and from the main storage.
(iii) Arithmetic and Logic Unit:
This unit performs the arithmetic operations such as addition, subtraction, multiplication and division. It also does logical operations such as comparison of numbers etc. Thus this unit helps by processing data and taking logical decisions.
3. Output unit:
After processing the data, the computer has to provide the result of the processing to the user. For this, computer uses output devices. The output device is that device which is used to provide the user with the desired output. Commonly used output devices are VDU (visual display unit) i.e. monitor, printers, plotter, magnetic media like floppy, hard disks etc.Q: what are the Generations of Computer? |
Computers generations were distinguish on the basis of hardware and software.
First Generation Computers (1951-1958):
The first generation computers were made up of vaccum tubes. Each computer had as many as thousands of vaccum tubes and hence the first generation computers were extremely large in size and require more space. These computers generated considerable amount of heat and poor reliability. These required constant maintenance.
To enter data into the computer punch cards were used. Punch card is a sheet of thick paper, in which holes are punched accordingly to a coding scheme.
Second Generation Computers (1959-1964):
With the invention of junction transistors, the vacuum tubes were replaced by transistors. Transistors were more reliable, small in size and required low power when compared with vacuum tubes. The second- generation computers were faster and had increased storage capacity. In the second-generation computers, in addition to the main memory an external or auxiliary storage device like magnetic tapes, magnetic disks were used. Second generation computers lead to the development of high level languages like
FORTRANà Formula Translation
COBOL à Common Business Oriented Language
ALGOL àAlgorithemic Language
APL àA Programming Language
Third Generation Computers (1965 - 1971):
Integrated circuits (IC) were introduced in 1960’s. In an IC, hundreds of transistors were incorporated on a single silicon chip and hence with IC’s computers could be made even small, more reliable and less expensive. After few years of invention of IC’s they were used as main memory. The magnetic discs replaced the magnetic tapes for auxiliary memory.
Fourth generation computers (1971 - present):
In the early 1970’s development of microprocessors revolutionized the computer industry. Very large scale integration (VLSI) and very high speed integration circuits led to the development of microcomputers. These circuits improved the performance of the computer in various aspects like speed, reliability and stability. These occupy less space and required no air- conditioning. With the advent of microprocessors, personal computers were developed. These are user friendly and are very easy to operate. The most popular integrated circuits used for personal computers are Intel’s 8008,8080,8085,8086 and Zilog’s Z-80.
Fifth generation computers:
Computers with capabilities to think reasonably make judgments, take decisions with artificial intelligence have the potential to change the world. These computers are classified as fifth generation computers. Very large scale integration will have millions of components on a single chip available at very low cost. Communication between user and systems is likely to be able to emulate performance of human brain where thinking computers will open new horizons in computing arena.
Q: Explain the Classification of computers: |
Computers can be classified into three categories according to the logic used. these are
a) Analog Computers b)Digital Computer s c)Hybrid Computers
a) Analog Computers
An analog computer is a form of computer that uses continuous physical phenomena such as electrical, mechanical, or hydraulic quantities to model the problem being solved.
Examples: Thermometers, speedometers, barometers etc.
b) Digital Computers
A computer that performs calculations and logical operations with quantities represented as digits, usually in the binary number system. Examples: Adding machines, pocket calculator and personal computer. Digital computers are further grouped into two categories
1. General purpose computers: The digital computers, which can theoretically be used for any type of application, are called general-purpose digital computers. These computers can be used in solving a business problem as well as mathematical equation with same accuracy and consistency.
Example: The computers that are used for payroll, graphs, analysis, account, banking etc.
2. Special purpose computers:
These are those digital computers, which are designed, made and used for specific job. These are usually used for those purposes, which are critical, and need great accuracy and response like satellite launching, weather forecasting etc.
3. Hybrid computers:
Hybrid computers combine the best features of analog and digital computers. They have the speed of analog and the accuracy of digital computers. They are usually used for special problems in which input data derived from measurements is converted into digits and processed by the computers. The computer can act like an analog computer converting measurement into numeric input. It can act as a digital computer processing stored data for management.
Q) What are shapes of computers(OR) What are the different types of Computer |
Ans: There are both large and small computers. Large computer system: They have been traditionally divided into three main categories
1. super computers
2. Main-frame computers
3. Mini computers
4. Micro computers
1. Super computer: The fastest type of computer. Supercomputers are very expensive and are employed for specialized applications that require immense amounts of mathematical calculations. For example, weather forecasting requires a supercomputer. Other uses of supercomputers include animated graphics, fluid dynamic calculations, nuclear energy research, and petroleum exploration.
Example: The most powerful Super Computer today, the CRAY-2 is setup in a C-shape, it is not as tall as a person and is small enough to fit in the space of a large business desk.
2. Main Frame Computers: A very large and expensive computer capable of supporting hundreds, or even thousands, of users simultaneously. In the hierarchy that starts with a simple microprocessor (in watches, for example) at the bottom and moves to supercomputers at the top, mainframes are just below supercomputers. In some ways, mainframes are more powerful than supercomputers because they support more simultaneous programs. But supercomputers can execute a single program faster than a mainframe.
Example: Mainframes are used by banks and many businesses to update inventory etc.,
3. Mini Computers: A midsized computer. In size and power, minicomputers lie between workstations and mainframes. In the past decade, the distinction between large minicomputers and small mainframes has blurred, however, as has the distinction between small minicomputers and workstations. But in general, a minicomputer is a multiprocessing system capable of supporting from 4 to about 200 users simultaneously.
Example: IBM AS 400
4. Personal Computers or Micro Computers:: A microcomputer is the smallest, least expensive of all the computers. The prefix micro re fers mainly to the physical size of the computer and its circuitry rather than its capabilities. The essential differences between micro computers and mainframe or mini computers are that micro computers has smallest memory and less power and are physically smaller and permit fewer peripherals to be attached.
Microcomputers available in different capabilities and size are
1. Desktop Models
2. Notebook Computers
3. Personal Digital Assistance 
Q) Explain briefly about input devices? |
Ans: Input device:
· Input is data or instructions that we enter into the memory of the computer.
· Once input is in memory, the CPU can access it and process the input into output.
· Input devices are used to load input data or programs or commands and user responses into a computer.
Most computers have several input devices. These are
1. Keyboard
2. Mouse
3. Joystick
4. Touch screen
5. Scanners
6. Digital Camera
7. Microphone
8. Bio-metric input devices
1) Keyboard
· The most common type of input device. User enters information by typing/pressing the appropriate keys.
· Most desktops have 101 to 105 keys, while laptops etc have fewer keys.
Types of keyboards
§ alphanumeric - letters, numbers, special keys (func, ctrl, alt etc.)
§ QWERTY – due to the layout of the letter keys
§ DVORAK – has an alternative layout designed to improve typing speed. The most frequently used keys are placed in the middle
§ Enhanced – have 12 function keys, 2 CTRL keys, 2 ALT keys and a set of arrow and additional keys.
§ Wireless – transmit data via infrared light waves
2) Mouse
· A pointing device allows you to control a pointer on the screen. This allows you to move or select items on a screen.
Types of Mouses
§ Mechanical mouse – the ball is at the bottom
§ Optical mouse – it emits and senses light to detect movement.
§ Cordless/wireless – uses infrared or radio waves
§ Touchpad/track pad – an area on a laptop where the finger is used. It is sensitive to pressure and motion.
3) Joystick
· A vertical lever (like gear stick in a car) mounted on a base.
· Moves graphics cursor/pointer in direction stick is pushed.
· Commonly used for video games.
· Has buttons called triggers to activate certain events.
4) Touch screen
· This is a monitor that has a touch sensitive panel.
· We can interact by touching the screen with our finger.
· These are often used in ATMs, hotels, stores, airports.
5) Scanners
· A light sensitive device that converts images into digital data that the computer can understand and represent on the screen.
6) Digital camera
· Allows taking pictures and storing the photographed images digitally instead of traditional film.
7) Microphone - Voice/Speech Recognition (Voice Data Entry)
· Spoken word translated to digital form.
· Mostly used by doctors, lawyers, journalists, physically disabled.
· Used for security and access control.
8) Biometric input devices
These devices, such as retinal scanner, fingerprint scanner read bodily features. They are mostly used in high security areas such as airports .
Q) Explain different types of output devices. |
Ans: Output device:
· An output device gives information to a user.
· Output can either be softcopy or hardcopy.
These are as follows
1. Monitor
2. Speaker
3. Plotter
4. Printer
1) Monitor /Video/Visual Display Unit (VDU):
1. The VDU is also called screen, monitor.
2. A typical screen is 24 lines by 80 chars per line.
3. Produces soft copy – because it exists electronically and is displayed for a temporary period of time.
Types of monitors
(1) cathode ray tube (CRT) (2)Liquid crystal display (LCD) (3)Light emitting diode (LED)
2. Printer:
· After a document is created on the computer, it can be sent to a printer for a hard copy (printout).
· Printers grouped in 2 functional categories:-
(a) Impact Printer (b)Non – Impact printer
a) Impact printer: - This is the most widely used. The print mechanism strikes the paper thru an ink ribbon which makes char impression on the page. Impact printers use solid font mechanisms or dot matrix mechanisms.
Ex: Dot matrix printer, Daisy wheel printer
b) Non-impact printer:- Uses thermal (heat), photographic (xerographic), electrostatic, light to print. Does not require physical contact with the paper and generally results in very high speeds. Tend to be more expensive. Do not have multiple copy facilities.
Ex: Thermal printer, Ink jet printer, Laser printer
Some of the most commonly used printers are:
(A) Dot Matrix Printer (B) Daisy Wheel (C) Laser (D) Ink-jet
a) Dot Matrix printer:
· These are the most popular and widely used low speed printers in use today.
· Relatively inexpensive. Limited by speed, noise, quality.
· Wide range of character sets.
· Prints a pattern of dots in shape of desired char.
· Print head is a matrix of steel pins. The higher the number of pins the better the quality print. 18 pin.or 24 pin.
· Color ribbons are available. Colors cannot be blended for new colors.
b) Daisy Wheel
· High quality print.
· Wheel rotated to print each char. The appropriate spoke is struck against an inked ribbon.
· Some can print left to right on one line and right to left on next line so printing is faster.
c) Laser
· Tend to be most expensive non impact.
· Very high quality.
· Uses electrostatic or optical methods. Uses toner powder (dried ink) which sticks to charged parts (on drum) traced by laser beam.
· Paper pressed against drum. Images permanently fused to the paper using a heating unit.
· Image of whole page represented by series of minute dots, dots are so close together that print looks like a shaped char (so high quality).
d) Ink-Jet Printer
· It uses a matrix of ink dots sprayed on paper to form a character from 50 nozzles.
· It uses small ink drops so more drops are needed to form a character so the resolution of the character is greater than a dot matrix. (300-600 dpi - dots per inch).
· Able to change the size and style of type/font almost instantaneously.
4. Plotter:
· A plotter is a device that uses pens moving in various directions to produce text and graphics on paper.
· It differs from a printer in that it can produce continuous lines.
· Printers generate lines by printing a series of closely spaced dots. Electrostatic plotters use a row of charged wires (styli) to draw electrostatic patterns on specially coated paper and then fuses toner to the pattern.
· These are used in graphics, earthquake detection, lie detectors, heart monitors, for graphs, maps, CAD - computer aided design.
Q: What do you mean by Storage Devices? Explain its types. |
Ans: Storage Device Storage device is a device which stores the data. Data and instruction entered into a computer system thorough i/p system has to be stored inside the computer before actual procession starts. Then after processing again need to store output or result to at storage device. Two type of basic storage we have in computer are primary and secondary storage:
Primary Storage: Primary storage is a storage location that holds memory for short periods of times while the computer is on. For example, computer RAM (random-access memory) and cache are both examples of a primary storage device. This type of storage is the fastest type of memory in your computer and is used to store data while it’s being used. For example, when you open a program data is moved from the secondary storage into the primary storage. It is also known as internal memory and main memory.
Secondary Storage: Secondary storage is a storage medium that holds information until it is deleted or overwritten regardless if the computer has power. For example, a floppy disk drive and hard disk drive are both good examples of secondary storage devices.
As can be seen by the below picture there are three different types of storage on a computer, although primary storage is accessed much faster than secondary storage because of the price and size limitations secondary storage is used with today’s computers to store all your programs and your personal data. It is also known as external memory and auxiliary storage. Off-line storage in Fig could be considered secondary storage, we’ve separated these into their own category because these types of media can be easily removed from the computer and stored elsewhere.
Q: Explain few primary storage devices (or) semi - conductor memory? |
Ans: - Generally used primary storage devices are: 1) RAM 2)ROM 3)CACHE 4)REGISTERS
1. Random Access Memory (RAM): The primary storage is referred to as random access memory (RAM) because it is possible to randomly select and use any location of the memory directly store and retrieve data. It takes same time to any address of the memory as the first address. It is also called read/write memory. The storage of data and instructions inside the primary storage is temporary. It disappears from RAM as soon as the power to the computer is switched off. The memories, which lose their content on failure of power supply, are known as volatile memories .So now we can say that RAM is volatile memory.
2. Read Only Memory (ROM): There is another memory in computer, which is called Read Only Memory (ROM). Again it is the Ics inside the PC that form the ROM. The storage of program and data in the ROM is permanent. The ROM stores some standard processing programs supplied by the manufacturers to operate the personal computer. The ROM can only be read by the CPU but it cannot be changed. The basic input/output program is stored in the ROM that examines and initializes various equipment attached to the PC when the switch is made ON. The memories, which do not lose their content on failure of power supply, are known as non-volatile memories. ROM is non-volatile memory.
a. PROM There is another type of primary memory in computer, which is called Programmable Read Only Memory (PROM). You know that it is not possible to modify or erase programs stored in ROM, but it is possible for you to store your program in PROM chip. Once the program are written it cannot be changed and remain intact even if power is switched off. Therefore programs or instructions written in PROM or ROM cannot be erased or changed.
b. EPROM: This stands for Erasable Programmable Read Only Memory, which overcome the problem of PROM & ROM. EPROM chip can be programmed time and again by erasing the information stored earlier in it. Information stored in EPROM exposing the chip for some time ultraviolet light and it erases chip is reprogrammed using a special programming facility. When the EPROM is in use information can only be read.
c. EPROM: This stand for electrically erasable programmable read- only memory. EEPROM is a special type of PROM that can be erased by exposing it to an electrical charge. Like other types of PROM, EEPROM retains its contents even when the power is turned off. EPROM is similar to flash memory (sometimes called flash EEPROM). The principal difference is that EEPROM requires data to be written or erased one byte at a time whereas flash memory allows data to be written or erased in blocks. This makes flash memory faster
3. Cache Memory: The speed of CPU is extremely high compared to the access time of main memory. Therefore the performance of CPU decreases due to the slow speed of main memory. To decrease the mismatch in operating speed, a small memory chip is attached between CPU and Main memory whose access time is very close to the processing speed of CPU. It is called CACHE memory. CACHE memories are accessed much faster than conventional RAM. It is used to store programs or data currently being executed or temporary data frequently used by the CPU. So each memory makes main memory to be faster and larger than it really is. It is also very expensive to have bigger size of cache memory and its size is normally kept small.
4. Registers: The CPU processes data and instructions with high speed, there is also movement of data between various units of computer. It is necessary to transfer the processed data with high speed. So the computer uses a number of special memory units called registers. They are not part of the main memory but they store data or information temporarily and pass it on as directed by the control unit.
1. Input Unit: This is the process of entering data and programs in to the computer system. These devices translate data from human understandable form into electronic impulses, which are understood by the computer. The most common input device is the keyboard, mouse, joystick, scanner, digitizer etc.,
2. Central Processing Unit (CPU):
Once the data is accepted it is fed into central processing unit before the output is generated as data has to be processed, which is done by CPU. This unit of the computer is the brain of computer system, which does all the processing, calculations, problem solving and controls all other functions of all other elements of the computer. The CPU consists of the following three distinct units namely
(i) Memory Unit
(ii) The Control Unit
(iii) The Arithmetic and Logic Unit
(i)Memory Unit:
This is the unit where the data and results are stored. This unit consists of cells which are capable to store unit of information. These cells can be accessed as they are numbered sequentially, which are called addresses. This memory unit is usually referred as primary storage section.
(ii) The Control Unit:
This is that unit of CPU, which coordinates all the activities of each and every element of computer. It decodes the instructions given by various users and it sends commands and signals that determine the sequence of various instructions. Though this unit does not process data but it acts as the central system for data manipulation, as it controls the flow of data to and from the main storage.
(iii) Arithmetic and Logic Unit:
This unit performs the arithmetic operations such as addition, subtraction, multiplication and division. It also does logical operations such as comparison of numbers etc. Thus this unit helps by processing data and taking logical decisions.
3. Output unit:
After processing the data, the computer has to provide the result of the processing to the user. For this, computer uses output devices. The output device is that device which is used to provide the user with the desired output. Commonly used output devices are VDU (visual display unit) i.e. monitor, printers, plotter, magnetic media like floppy, hard disks etc.Q: what are the Generations of Computer? |
Computers generations were distinguish on the basis of hardware and software.
First Generation Computers (1951-1958):
The first generation computers were made up of vaccum tubes. Each computer had as many as thousands of vaccum tubes and hence the first generation computers were extremely large in size and require more space. These computers generated considerable amount of heat and poor reliability. These required constant maintenance.
To enter data into the computer punch cards were used. Punch card is a sheet of thick paper, in which holes are punched accordingly to a coding scheme.
Second Generation Computers (1959-1964):
With the invention of junction transistors, the vacuum tubes were replaced by transistors. Transistors were more reliable, small in size and required low power when compared with vacuum tubes. The second- generation computers were faster and had increased storage capacity. In the second-generation computers, in addition to the main memory an external or auxiliary storage device like magnetic tapes, magnetic disks were used. Second generation computers lead to the development of high level languages like
FORTRANà Formula Translation
COBOL à Common Business Oriented Language
ALGOL àAlgorithemic Language
APL àA Programming Language
Third Generation Computers (1965 - 1971):
Integrated circuits (IC) were introduced in 1960’s. In an IC, hundreds of transistors were incorporated on a single silicon chip and hence with IC’s computers could be made even small, more reliable and less expensive. After few years of invention of IC’s they were used as main memory. The magnetic discs replaced the magnetic tapes for auxiliary memory.
Fourth generation computers (1971 - present):
In the early 1970’s development of microprocessors revolutionized the computer industry. Very large scale integration (VLSI) and very high speed integration circuits led to the development of microcomputers. These circuits improved the performance of the computer in various aspects like speed, reliability and stability. These occupy less space and required no air- conditioning. With the advent of microprocessors, personal computers were developed. These are user friendly and are very easy to operate. The most popular integrated circuits used for personal computers are Intel’s 8008,8080,8085,8086 and Zilog’s Z-80.
Fifth generation computers:
Computers with capabilities to think reasonably make judgments, take decisions with artificial intelligence have the potential to change the world. These computers are classified as fifth generation computers. Very large scale integration will have millions of components on a single chip available at very low cost. Communication between user and systems is likely to be able to emulate performance of human brain where thinking computers will open new horizons in computing arena.
Q: Explain the Classification of computers: |
Computers can be classified into three categories according to the logic used. these are
a) Analog Computers b)Digital Computer s c)Hybrid Computers
a) Analog Computers
An analog computer is a form of computer that uses continuous physical phenomena such as electrical, mechanical, or hydraulic quantities to model the problem being solved.
Examples: Thermometers, speedometers, barometers etc.
b) Digital Computers
A computer that performs calculations and logical operations with quantities represented as digits, usually in the binary number system. Examples: Adding machines, pocket calculator and personal computer. Digital computers are further grouped into two categories
1. General purpose computers: The digital computers, which can theoretically be used for any type of application, are called general-purpose digital computers. These computers can be used in solving a business problem as well as mathematical equation with same accuracy and consistency.
Example: The computers that are used for payroll, graphs, analysis, account, banking etc.
2. Special purpose computers:
These are those digital computers, which are designed, made and used for specific job. These are usually used for those purposes, which are critical, and need great accuracy and response like satellite launching, weather forecasting etc.
3. Hybrid computers:
Hybrid computers combine the best features of analog and digital computers. They have the speed of analog and the accuracy of digital computers. They are usually used for special problems in which input data derived from measurements is converted into digits and processed by the computers. The computer can act like an analog computer converting measurement into numeric input. It can act as a digital computer processing stored data for management.
Q) What are shapes of computers(OR) What are the different types of Computer |
Ans: There are both large and small computers. Large computer system: They have been traditionally divided into three main categories
1. super computers
2. Main-frame computers
3. Mini computers
4. Micro computers
1. Super computer: The fastest type of computer. Supercomputers are very expensive and are employed for specialized applications that require immense amounts of mathematical calculations. For example, weather forecasting requires a supercomputer. Other uses of supercomputers include animated graphics, fluid dynamic calculations, nuclear energy research, and petroleum exploration.
Example: The most powerful Super Computer today, the CRAY-2 is setup in a C-shape, it is not as tall as a person and is small enough to fit in the space of a large business desk.
2. Main Frame Computers: A very large and expensive computer capable of supporting hundreds, or even thousands, of users simultaneously. In the hierarchy that starts with a simple microprocessor (in watches, for example) at the bottom and moves to supercomputers at the top, mainframes are just below supercomputers. In some ways, mainframes are more powerful than supercomputers because they support more simultaneous programs. But supercomputers can execute a single program faster than a mainframe.
Example: Mainframes are used by banks and many businesses to update inventory etc.,
3. Mini Computers: A midsized computer. In size and power, minicomputers lie between workstations and mainframes. In the past decade, the distinction between large minicomputers and small mainframes has blurred, however, as has the distinction between small minicomputers and workstations. But in general, a minicomputer is a multiprocessing system capable of supporting from 4 to about 200 users simultaneously.
Example: IBM AS 400
4. Personal Computers or Micro Computers:: A microcomputer is the smallest, least expensive of all the computers. The prefix micro re fers mainly to the physical size of the computer and its circuitry rather than its capabilities. The essential differences between micro computers and mainframe or mini computers are that micro computers has smallest memory and less power and are physically smaller and permit fewer peripherals to be attached.
Microcomputers available in different capabilities and size are
1. Desktop Models
2. Notebook Computers
3. Personal Digital Assistance Q)Explain Number system in computers (OR)
Write how to convert numbers
When we type some letters or words, the computer translates them in numbers as computers can understand only numbers. A computer can understand the positional number system where there are only a few symbols called digits and these symbols represent different values depending on the position they occupy in the number.
The value of each digit in a number can be determined using −
- The digit
- The position of the digit in the number
- The base of the number system (where the base is defined as the total number of digits available in the number system)
DECIMAL NUMBER SYSTEM
The number system that we use in our day-to-day life is the decimal number system. Decimal number system has base 10 as it uses 10 digits from 0 to 9. In decimal number system, the successive positions to the left of the decimal point represent units, tens, hundreds, thousands, and so on.Each position represents a specific power of the base (10). For example, the decimal number 1234 consists of the digit 4 in the units position, 3 in the tens position, 2 in the hundreds position, and 1 in the thousands position. Its value can be written as
(1 x 1000)+ (2 x 100)+ (3 x 10)+ (4 x l) (1 x 103)+ (2 x 102)+ (3 x 101)+ (4 x l00) 1000 + 200 + 30 + 4 1234As a computer programmer or an IT professional, you should understand the following number systems which are frequently used in computers.
| S.No. | Number System and Description |
|---|---|
| 1 | Binary Number System Base 2. Digits used : 0, 1 |
| 2 | Octal Number System Base 8. Digits used : 0 to 7 |
| 3 | Hexa Decimal Number System Base 16. Digits used: 0 to 9, Letters used : A- F |
BINARY NUMBER SYSTEM
Characteristics of the binary number system are as follows −- Uses two digits, 0 and 1
- Also called as base 2 number system
- Each position in a binary number represents a 0 power of the base (2). Example 20
- Last position in a binary number represents a x power of the base (2). Example 2x where x represents the last position - 1.
Example
Binary Number: 101012Calculating Decimal Equivalent −
| Step | Binary Number | Decimal Number |
|---|---|---|
| Step 1 | 101012 | ((1 x 24) + (0 x 23) + (1 x 22) + (0 x 21) + (1 x 20))10 |
| Step 2 | 101012 | (16 + 0 + 4 + 0 + 1)10 |
| Step 3 | 101012 | 2110 |
OCTAL NUMBER SYSTEM
Characteristics of the octal number system are as follows −- Uses eight digits, 0,1,2,3,4,5,6,7
- Also called as base 8 number system
- Each position in an octal number represents a 0 power of the base (8). Example 80
- Last position in an octal number represents a x power of the base (8). Example 8x where x represents the last position - 1
Example
Octal Number: 125708Calculating Decimal Equivalent −
| Step | Octal Number | Decimal Number |
|---|---|---|
| Step 1 | 125708 | ((1 x 84) + (2 x 83) + (5 x 82) + (7 x 81) + (0 x 80))10 |
| Step 2 | 125708 | (4096 + 1024 + 320 + 56 + 0)10 |
| Step 3 | 125708 | 549610 |
HEXADECIMAL NUMBER SYSTEM
Characteristics of hexadecimal number system are as follows −- Uses 10 digits and 6 letters, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F
- Letters represent the numbers starting from 10. A = 10. B = 11, C = 12, D = 13, E = 14, F = 15
- Also called as base 16 number system
- Each position in a hexadecimal number represents a 0 power of the base (16). Example, 160
- Last position in a hexadecimal number represents a x power of the base (16). Example 16x where x represents the last position - 1
Example
Hexadecimal Number: 19FDE16Calculating Decimal Equivalent −
| Step | Binary Number | Decimal Number |
|---|---|---|
| Step 1 | 19FDE16 | ((1 x 164) + (9 x 163) + (F x 162) + (D x 161) + (E x 160))10 |
| Step 2 | 19FDE16 | ((1 x 164) + (9 x 163) + (15 x 162) + (13 x 161) + (14 x 160))10 |
| Step 3 | 19FDE16 | (65536+ 36864 + 3840 + 208 + 14)10 |
| Step 4 | 19FDE16 | 10646210 |
UNIT-II
Q) Explain briefly about input devices? |
Ans: Input device:
· Input is data or instructions that we enter into the memory of the computer.
· Once input is in memory, the CPU can access it and process the input into output.
· Input devices are used to load input data or programs or commands and user responses into a computer.
Most computers have several input devices. These are
1. Keyboard
2. Mouse
3. Joystick
4. Touch screen
5. Scanners
6. Digital Camera
7. Microphone
8. Bio-metric input devices
1) Keyboard
· The most common type of input device. User enters information by typing/pressing the appropriate keys.
· Most desktops have 101 to 105 keys, while laptops etc have fewer keys.
Types of keyboards
§ alphanumeric - letters, numbers, special keys (func, ctrl, alt etc.)
§ QWERTY – due to the layout of the letter keys
§ DVORAK – has an alternative layout designed to improve typing speed. The most frequently used keys are placed in the middle
§ Enhanced – have 12 function keys, 2 CTRL keys, 2 ALT keys and a set of arrow and additional keys.
§ Wireless – transmit data via infrared light waves
2) Mouse
· A pointing device allows you to control a pointer on the screen. This allows you to move or select items on a screen.
Types of Mouses
§ Mechanical mouse – the ball is at the bottom
§ Optical mouse – it emits and senses light to detect movement.
§ Cordless/wireless – uses infrared or radio waves
§ Touchpad/track pad – an area on a laptop where the finger is used. It is sensitive to pressure and motion.
3) Joystick
· A vertical lever (like gear stick in a car) mounted on a base.
· Moves graphics cursor/pointer in direction stick is pushed.
· Commonly used for video games.
· Has buttons called triggers to activate certain events.
4) Touch screen
· This is a monitor that has a touch sensitive panel.
· We can interact by touching the screen with our finger.
· These are often used in ATMs, hotels, stores, airports.
5) Scanners
· A light sensitive device that converts images into digital data that the computer can understand and represent on the screen.
6) Digital camera
· Allows taking pictures and storing the photographed images digitally instead of traditional film.
7) Microphone - Voice/Speech Recognition (Voice Data Entry)
· Spoken word translated to digital form.
· Mostly used by doctors, lawyers, journalists, physically disabled.
· Used for security and access control.
8) Biometric input devices
These devices, such as retinal scanner, fingerprint scanner read bodily features. They are mostly used in high security areas such as airports .
Q) Explain different types of output devices. |
Ans: Output device:
· An output device gives information to a user.
· Output can either be softcopy or hardcopy.
These are as follows
1. Monitor
2. Speaker
3. Plotter
4. Printer
1) Monitor /Video/Visual Display Unit (VDU):
1. The VDU is also called screen, monitor.
2. A typical screen is 24 lines by 80 chars per line.
3. Produces soft copy – because it exists electronically and is displayed for a temporary period of time.
Types of monitors
(1) cathode ray tube (CRT) (2)Liquid crystal display (LCD) (3)Light emitting diode (LED)
2. Printer:
· After a document is created on the computer, it can be sent to a printer for a hard copy (printout).
· Printers grouped in 2 functional categories:-
(a) Impact Printer (b)Non – Impact printer
a) Impact printer: - This is the most widely used. The print mechanism strikes the paper thru an ink ribbon which makes char impression on the page. Impact printers use solid font mechanisms or dot matrix mechanisms.
Ex: Dot matrix printer, Daisy wheel printer
b) Non-impact printer:- Uses thermal (heat), photographic (xerographic), electrostatic, light to print. Does not require physical contact with the paper and generally results in very high speeds. Tend to be more expensive. Do not have multiple copy facilities.
Ex: Thermal printer, Ink jet printer, Laser printer
Some of the most commonly used printers are:
(A) Dot Matrix Printer (B) Daisy Wheel (C) Laser (D) Ink-jet
a) Dot Matrix printer:
· These are the most popular and widely used low speed printers in use today.
· Relatively inexpensive. Limited by speed, noise, quality.
· Wide range of character sets.
· Prints a pattern of dots in shape of desired char.
· Print head is a matrix of steel pins. The higher the number of pins the better the quality print. 18 pin.or 24 pin.
· Color ribbons are available. Colors cannot be blended for new colors.
b) Daisy Wheel
· High quality print.
· Wheel rotated to print each char. The appropriate spoke is struck against an inked ribbon.
· Some can print left to right on one line and right to left on next line so printing is faster.
c) Laser
· Tend to be most expensive non impact.
· Very high quality.
· Uses electrostatic or optical methods. Uses toner powder (dried ink) which sticks to charged parts (on drum) traced by laser beam.
· Paper pressed against drum. Images permanently fused to the paper using a heating unit.
· Image of whole page represented by series of minute dots, dots are so close together that print looks like a shaped char (so high quality).
d) Ink-Jet Printer
· It uses a matrix of ink dots sprayed on paper to form a character from 50 nozzles.
· It uses small ink drops so more drops are needed to form a character so the resolution of the character is greater than a dot matrix. (300-600 dpi - dots per inch).
· Able to change the size and style of type/font almost instantaneously.
4. Plotter:
· A plotter is a device that uses pens moving in various directions to produce text and graphics on paper.
· It differs from a printer in that it can produce continuous lines.
· Printers generate lines by printing a series of closely spaced dots. Electrostatic plotters use a row of charged wires (styli) to draw electrostatic patterns on specially coated paper and then fuses toner to the pattern.
· These are used in graphics, earthquake detection, lie detectors, heart monitors, for graphs, maps, CAD - computer aided design.
Q: What do you mean by Storage Devices? Explain its types. |
Ans: Storage Device Storage device is a device which stores the data. Data and instruction entered into a computer system thorough i/p system has to be stored inside the computer before actual procession starts. Then after processing again need to store output or result to at storage device. Two type of basic storage we have in computer are primary and secondary storage:
Primary Storage: Primary storage is a storage location that holds memory for short periods of times while the computer is on. For example, computer RAM (random-access memory) and cache are both examples of a primary storage device. This type of storage is the fastest type of memory in your computer and is used to store data while it’s being used. For example, when you open a program data is moved from the secondary storage into the primary storage. It is also known as internal memory and main memory.
Secondary Storage: Secondary storage is a storage medium that holds information until it is deleted or overwritten regardless if the computer has power. For example, a floppy disk drive and hard disk drive are both good examples of secondary storage devices.
As can be seen by the below picture there are three different types of storage on a computer, although primary storage is accessed much faster than secondary storage because of the price and size limitations secondary storage is used with today’s computers to store all your programs and your personal data. It is also known as external memory and auxiliary storage. Off-line storage in Fig could be considered secondary storage, we’ve separated these into their own category because these types of media can be easily removed from the computer and stored elsewhere.
Q: Explain few primary storage devices (or) semi - conductor memory? |
Ans: - Generally used primary storage devices are: 1) RAM 2)ROM 3)CACHE 4)REGISTERS
1. Random Access Memory (RAM): The primary storage is referred to as random access memory (RAM) because it is possible to randomly select and use any location of the memory directly store and retrieve data. It takes same time to any address of the memory as the first address. It is also called read/write memory. The storage of data and instructions inside the primary storage is temporary. It disappears from RAM as soon as the power to the computer is switched off. The memories, which lose their content on failure of power supply, are known as volatile memories .So now we can say that RAM is volatile memory.
2. Read Only Memory (ROM): There is another memory in computer, which is called Read Only Memory (ROM). Again it is the Ics inside the PC that form the ROM. The storage of program and data in the ROM is permanent. The ROM stores some standard processing programs supplied by the manufacturers to operate the personal computer. The ROM can only be read by the CPU but it cannot be changed. The basic input/output program is stored in the ROM that examines and initializes various equipment attached to the PC when the switch is made ON. The memories, which do not lose their content on failure of power supply, are known as non-volatile memories. ROM is non-volatile memory.
a. PROM There is another type of primary memory in computer, which is called Programmable Read Only Memory (PROM). You know that it is not possible to modify or erase programs stored in ROM, but it is possible for you to store your program in PROM chip. Once the program are written it cannot be changed and remain intact even if power is switched off. Therefore programs or instructions written in PROM or ROM cannot be erased or changed.
b. EPROM: This stands for Erasable Programmable Read Only Memory, which overcome the problem of PROM & ROM. EPROM chip can be programmed time and again by erasing the information stored earlier in it. Information stored in EPROM exposing the chip for some time ultraviolet light and it erases chip is reprogrammed using a special programming facility. When the EPROM is in use information can only be read.
c. EPROM: This stand for electrically erasable programmable read- only memory. EEPROM is a special type of PROM that can be erased by exposing it to an electrical charge. Like other types of PROM, EEPROM retains its contents even when the power is turned off. EPROM is similar to flash memory (sometimes called flash EEPROM). The principal difference is that EEPROM requires data to be written or erased one byte at a time whereas flash memory allows data to be written or erased in blocks. This makes flash memory faster
3. Cache Memory: The speed of CPU is extremely high compared to the access time of main memory. Therefore the performance of CPU decreases due to the slow speed of main memory. To decrease the mismatch in operating speed, a small memory chip is attached between CPU and Main memory whose access time is very close to the processing speed of CPU. It is called CACHE memory. CACHE memories are accessed much faster than conventional RAM. It is used to store programs or data currently being executed or temporary data frequently used by the CPU. So each memory makes main memory to be faster and larger than it really is. It is also very expensive to have bigger size of cache memory and its size is normally kept small.
4. Registers: The CPU processes data and instructions with high speed, there is also movement of data between various units of computer. It is necessary to transfer the processed data with high speed. So the computer uses a number of special memory units called registers. They are not part of the main memory but they store data or information temporarily and pass it on as directed by the control unit.
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