Computer Systems

1.

Storage media are devices that store application and user information. The primary storage media for a computer is usually the internal hard drive. Most internal drives are regular IDE hard drives that come with the computer. A removable drive is another popular storage device that is usually connected by fire wire, USB, or parallel port (e.g. portable Zip drives, Jaz drives, or CD/DVD drives). Newer forms of external storage include USB thumb drives and camera storage media.

Floppy discs are magnetic and use magnetism to store data. CD drives are optical and read pits in a reflective surface using a laser. CD's have a much higher data density than floppy discs. CD's are a much higher capacity and can be read at much higher speeds than floppy discs.

2.

A memory is a storage device of computer that stores any types of data and information. A memory system can be logically divided into two categories. They are explained below:

1. Primary memory: The primary memory of computer is also called main memory of computer. It is fast and less capacity memory of computer. The primary memories of computer are ROM, RAM, cache memory, etc. they are mainly used to store data during a time of processing.

2. Secondary memory: It is also known as secondary storage. It is slower and cheaper form of memory. CPU does not access the secondary memory directly. The content in it must first copy into the primary storage RAM for CPU to process. It includes hard-drives, floppy disks, CDs etc. It is used to store the programs and data for long term.

3.

A computer peripheral is a device that is connected to a computer but is not part of the core computer architecture.

Different types of printers are described below:

1. Dot matrix- printer: Dot matrix printer is an impact printer that produces text and graphics when tiny wire pins on the print head strike the ink ribbon. The print head runs back and forth on the paper like a typewriter. When the ink ribbon presses on the paper, it creates dots that form text and images.

Advantages :

1. Can print on multi-part forms or carbon copies.
2. Low printing cost per page.
3. Reliable, durable.

Disadvantages :

1. Noisy.< /P>
2. Limited print quality.
3. Low printing speed.
4. Limited color printing.

2. Inkjet printers: These are non-impact printers which print text and images by spraying tiny droplets of liquid ink onto paper. They are the most popular printers for home use.

Advantages :

1. Low cost.
2. High quality of output, fine and smooth printing.
3. Good color printing
4. Easy to use.
5. Faster in processing

Disadvantages :

1. Print head is less durable.
2. Expensive replacement ink cartridges.
3. Not good for high volume printing.
4. Cannot use highlighter marker on inkjet printouts.

3. Laser printers: Laser printers are non-impact printers which can print text and images in high speed and high quality resolution, ranging from 600 to 1200 dpi.

Advantages :

1. High resolution.
2. High print speed.
3. No smearing.
4. Cheap printing
5. Good for high volume printing.

Disadvantages :

1. They are more expensive than inkjet printers.
2. Except for high end machines, laser printers are less capable of printing vivid colors and high quality images such as photos.
3. They cost of toner replacement and drum replacement is high.
4. Warm up time is needed.

4.

The nature of having information lost from the memory devices after the power is switched off is called volatility.

1. RAM: It refers to Random Access Memory. Random Access Memory is a form of computer data storage. The word 'RAM' is often associated with the volatile types of memory where the information is lost after the power is switched off. The advantage of using RAM is store whatever you're working on at nay moment and RAM is very fast memory.

2. ROM: It refers to Read Only Memory. It is manufactured by company while design it. Data stored in ROM cannot be modified, or can be modified only slowly or with difficulty. So it is mainly used to distribute firmware. The manufacturing company already installed program in ROM.

5.

The components of computer are interacted by bus. There are different types of bus structure. The bus is a medium used to transfer data, memory address and control signal from one part to other part of computers. There are three types of bus which are described below:

1. Address Bus: It is a group of wires or lines that are used to transfer the addresses of memory or I/O devices. It is unidirectional.
2. Data Bus: It is used to transfer data within microprocessor and memory/input or output devices. It is bidirectional as microprocessor requires sending or receiving data.
3. Control Bus: A control bus is a computer bus used by the CPU to communicate with devices that are contained within the computer. This occurs through physical connections such as cables or printed circuits.

6.

A computer system refers to the fully function able system that is integration of both hardware and software. The hardware components of a computer of a computer system are physical components that are tangible such as keyboard, mouse, processor, mother board, main memory, secondary memory, monitor, printer, etc. whereas the software components are logical components that make physical component work such as data, information, computer instructions etc.

1. Input unit: it accepts the data or instructions given by the user and it converts the data and instructions from man readable to machine readable code. Some common input devices are keyboard, mouse, scanner punched cards etc.

2. Processor/CPU: CPU is the portion of a computer system that carries out the instructions of a computer program, and is the primary element carrying out the computer's functions. Some of the primary components of a CPU are:

1. Registers: These are the primary memory of computer system. They are mainly used to store data during the time of processing inside ALU. The registers within CPU are special purpose temporary storage locations.
2. Control unit: The control unit is the brain of the CPU itself. It controls overall operations and devices of computer.
3. Arithmetic Logic Unit: ALU carries out the arithmetic and logical operations on the data made available to it.

3. Main Memory: It is a volatile memory of computer. As soon as a computer starts, primary memory stores all running applications, operating system, user interface and any others. Its storage capacity is smaller but faster.

4. Auxiliary storage: It is the secondary memory of computer. They have slower access rates but greater storage capacity and data stability. Auxiliary memory holds programs and data for future use because it is non-volatile.

5. Output Unit: When the computer its processing task, the results must be conveyed back to the user. Information from the CPU is converted into an understandable form through output devices.

7.

a. Hardware: Hardware, in the computer world, refers to the physical components that make up a computer system. There are many different kinds of hardware that can be installed inside, and connected to the outside, of a computer.

b. Software: Software is the collection of computer programs, procedures and documentation that performs different tasks on a computer system. The types of software are system software and application software.

c. Firmware: Software (programs or data) that has been written onto read-only memory (ROM). Firmware is a combination of software and hardware. ROMs, PROMs and EPROMs that have data or programs recorded on them are firmware.

8.

a. Touch pad: Alternatively referred to as a glide pad, glide point, pressure sensitive tablet, or track pad, a touchpad is an input device found on the majority of portable computers, and now also available with some external keyboards, that allow you to move the mouse cursor without the need of an external mouse.

A touchpad is operated by using your finger and dragging it across a flat surface; as you move your finger on the surface, the mouse cursor will move in that same direction, and like most computer mice, the touchpad also has two buttons below the touch surface that enables you to click like a standard mouse.

b. Light pens: A light pen is a computer input device in the form of a light-sensitive wand used in conjunction with a computer's CRT TV set or monitor. It allows the user to point to displayed objects, or draw on the screen, in a similar way to a touch screen but with greater positional accuracy. A light pen can work with any CRT-based display, but not with LCD screens (though Toshiba and Hitachi displayed a similar idea at the "Display 2006" show in Japan), projectors and other display devices.

A light pen is fairly simple to implement. Just like a light gun, a light pen works by sensing the sudden small change in brightness of a point on the screen when the electron gun refreshes that spot. By noting exactly where the scanning has reached at that moment, the X,Y position of the pen can be resolved. This is usually achieved by the light pen causing an interrupt, at which point the scan position can be read from a special register, or computed, from a counter or timer. The pen position is updated on every refresh of the screen.

9.

Serial transmissions only use 2 wires for transmitting and receiving data, and only 1 for sending or receiving, and can only send one bit at a time. Parallel cables use several wires for data transmission and is much faster than serial thus 8 or more wires are carrying data parallel to each other to it's destination.

serial data transmission:

data (8 bits)

transmit -----------010101010-----------------> single line to transmit on

receive <--------------------------- single line to receive on

Parallel data transmission (80 bits) :

transmit multiple lines simultaneously

010101001----------->

-----------010101010----------- >

-----------010101010----------- >

-----------010101001----------- >

-----------010101010----------- >

-----------010101010----------- >

-----------010101001----------- >

-----------010101010----------- >

-----------010101010----------- >

-----------010101001----------- >

10.

Computer architecture is a specification detailing how a set of software and hardware technology standards interact to form a computer system or platform. In short, computer architecture refers to how a computer system is designed and what technologies it is compatible with.

1. Input unit: it accepts the data or instructions given by the user and it converts the data and instructions from man readable to machine readable code. Some common input devices are keyboard, mouse, scanner punched cards etc.
2. Processor/CPU: CPU is the portion of a computer system that carries out the instructions of a computer program, and is the primary element carrying out the computer's functions. Some of the primary components of a CPU are:

1. Registers: These are the primary memory of computer system. They are mainly used to store data during the time of processing inside ALU. The registers within CPU are special purpose temporary storage locations.
2. Control unit: The control unit is the brain of the CPU itself. It controls overall operations and devices of computer.
3. Arithmetic Logic Unit: ALU carries out the arithmetic and logical operations on the data made available to it.

3. Main Memory: It is a volatile memory of computer. As soon as a computer starts, primary memory stores all running applications, operating system, user interface and any others. Its storage capacity is smaller but faster.

4. Auxiliary storage: It is the secondary memory of computer. They have slower access rates but greater storage capacity and data stability. Auxiliary memory holds programs and data for future use because it is non-volatile.

5. Output Unit: When the computer its processing task, the results must be conveyed back to the user. Information from the CPU is converted into an understandable form through output devices.

11.

The control unit is a component of a computer's central processing unit (CPU) that directs operation of the processor. It controls communication and co-ordination between input/output devices. It reads and interprets instructions and determines the sequence for processing the data.

It directs the operation of the other units by providing timing and control signals. All computer resources are managed by the CU (Control Unit). It directs the flow of data between the Central Processing Unit (CPU) and the other devices. The control unit was historically defined as one distinct part of the 1946 reference model of Von Neumann architecture. In modern computer designs, the control unit is typically an internal part of the CPU with its overall role and operation unchanged.

An ALU performs basic arithmetic and logic operations. Examples of arithmetic operations are addition, subtraction, multiplication, and division. Examples of logic operations are comparisons of values such as NOT, AND, and OR.

The inputs to the ALU are the data to be operated on (called operands) and a code from the control unit indicating which operation to perform. Its output is the result of the computation.

12.

The types of memory in a computer system are:

1. Cache memory: A CPU cache is a cache used by the central processing unit (CPU) of a computer to reduce the average time to access data from the main memory. The cache is a smaller, faster memory which stores copies of the data from frequently used main memory locations. Most CPUs have different independent caches, including instruction and data caches, where the data cache is usually organized as a hierarchy of more cache levels (L1, L2 etc.)

2. Primary memory: Primary storage, also known as main storage or memory, is the area in a computer in which data is stored for quick access by the computer's processor. The terms random access memory (RAM) and memory are often as synonyms for primary or main storage.

3. Secondary memory: Secondary memory or external memory is used to store a large amount of data at lesser cost per byte than primary memory. They are two orders of magnitude less expensive than primary storage. In addition, secondary storage does not lose the data when the device is powered down. It is non-volatile. Another difference from primary storage in that it is not directly accessible by the CPU, they are accessed via the input/output channels. The most common form of auxiliary memory devices used in consumer systems is flash memory, optical discs, and magnetic disks.

13.

A peripheral device is generally defined as any auxiliary device such as a computer mouse or keyboard that connects to and works with the computer in some way. Other examples of peripherals are expansion cards, graphics cards, image scanners, tape drives, microphones, loudspeakers, webcams, and digital cameras.

Accessing data sequentially is much faster than accessing it randomly because of the way in which the disk hardware works. The seek operation, which occurs when the disk head positions itself at the right disk cylinder to access data requested, takes more time than any other part of the I/O process. Because reading randomly involves a higher number of seek operations than does sequential reading, random reads deliver a lower rate of throughput. The same is true for random writing.

14.

Input devices are the hardware that gives computers instructions. Output devices relay the response from the computer in the form of a visual response (monitor), sound (speakers) or media devices (CD or DVD drives). The purpose of these devices is to translate the machine's response to a usable form for the computer user.

Some of the input devices are as:

1. Keyboard: A computer keyboard is an important device that allows a person to enter symbols like letters and numbers into a computer. It is the main input device for most computers.
2. Mouse: A computer mouse is an input device that is most often used with a personal computer. Moving a mouse along a flat surface can move the on-screen cursor to different items on the screen. Items can be moved or selected by pressing the mouse buttons (called clicking).
3. Scanner
4. Joystick
5. Light pen

Some of the output devices as:

1. Monitor: The monitor is the piece of computer hardware that displays the video and graphics information generated by the computer through the video card.
2. Printer: External device that communicates with another digital device to print what a user sees on a screen. Printers use small pixels to transfer an image from the system to another surface. Ink jet and laser printers are the most commonly used varieties of this device, and are most commonly hooked up to a personal computer. Some printers only print in black and white, but most include a color option as well.
3. Plotter
4. Speaker
5. Modem

15.

The differences between them are as:

Impact printer	Non-impact printer
They all need physical contact with paper to print	They do not need to physically strike ink onto paper
Typically have no, or limited, options for different fonts, colors and graphics, and print quality may be low.	Can print exactly what appears on a computer screen at a high quality.
Impact printers can also print carbon copies and multipart forms, as the strike of the pin or hammer carries through from the top copy to those underneath.	This is not possible with non-impact products as they do not physically touch the paper with any force.
Impact printers tend to be cheaper to run than non-impact models. They use less complex consumables and have fewer mechanical parts, so may be less prone to breaking down.	Non-impact printers typically cost more to run, especially if you print pages that are heavy in color, graphics, images and photos.

16.

Computer software is the collection of computer programs, procedures and documentation that performs different tasks on a computer system. The types of software are system software and application software. They are as follows:

1. System software:

1. Operating system: Windows, Mac, DOS, etc.
2. Utility software: antivirus software, backup software, etc.
3. Language processor:

2. Application software:

1. Package software: word processing, database software, etc.
2. Tailored software: JAVA, C++, etc.

17.

Input devices refer to devices such as mice, keyboards, webcams and the microphone. Their main function is to allow the user to control the machine through data input. They are also a medium through which the user communicates with the computer.

The main functions of control unit of computer are as:

1. It carries out the controlling operations of computer.
2. It performs data processing operation.
3. It sends control signal to various parts of computer system for controlling.
4. It gives commands to input data from input unit to memory unit to ALU.
5. It transforms results from ALU to memory unit to output unit.
6. It gives command to store the data, instruction and program in memory.

18.

The functions of CPU are as follows:

1. It carries out the controlling operations of computer.
2. It performs data processing operation.
3. It sends control signal to various parts of computer system for controlling.
4. It gives commands to input data from input unit to memory unit to ALU.
5. It transforms results from ALU to memory unit to output unit.
6. It gives command to store the data, instruction and program in memory.
7. I t performs basic arithmetical calculations such as addition, subtraction, multiplication, etc.
8. It performs logical operations such as comparing greater than, equal to etc.

19.

Memory is a storage device of computer that stores any types of data and information. The memories are primary, secondary and cache.

The differences between primary and secondary memories are as:

1. Primary memory storages are temporary; where as the secondary storage is permanent.

2. Primary memory is expensive and smaller, where as secondary memory is cheaper and larger

3. Primary memory storages are faster, where as secondary storages are slower.

4. Primary memory storages are connected through data buses to CPU, where as the secondary storages are connect through data cables to CPU.

In addition to storing more data, a hard disk can provide much faster access to storage than a floppy disk. A hard disk rotates from 2,400 to 3,600 revolutions per minute (rpm) and is constantly spinning (except in laptops, which conserve battery life by spinning the hard disk only when in use). An ultra-fast hard disk has a separate read/write head over each track on the disk, so that no time is lost in positioning the head over the desired track; accessing the desired sector takes only milliseconds, the time it takes for the disk to spin to the sector. A floppy disk does not spin until a data transfer is requested, and the rotation speed is only about 300 rpm.

20.

An output device is any piece of computer hardware equipment used to communicate the results of data processing carried out by an information processing system (such as a computer) which converts the electronically generated information into human-readable form.

Soft copy output is the text/graphics that are displayed on the computer screen. Hard copy is the page on which the text/graphics have been printed in a printer and can be held in your hand.

21.

Software is the collection of computer programs, procedures and documentation that performs different tasks on a computer system. The types of software are system software and application software. The different types of software are as follows:

1. System software: It is software designed to operate the computer hardware to provide a platform for running application software it helps in running the computer hardware and the computer software.

1. Operating system: It is the most important program that runs on a computer. Every general purpose computer must have an operating system to run other programs.
2. Utility software: it helps to manage, maintain and control computer resources. Examples: virus scanning software, backup software, etc.
3. Language processor: it is a special type of computer system software that can use to translate the programs written in one language into another language.

2. Application software: it enables the user to accomplish certain specific tasks. It can use to solve application type of problem.

1. Package software: it is mainly designed by software companies to generalize the tasks. They are general purpose software. For examples: word processing software, database software, spreadsheet software, multimedia software, etc.
2. Tailored software: it is specific purpose software. It is also called small type of software. These types of software are developed for specific tasks. They are written in high level languages.

22.

a. RAM: it refers to read only memory that stores data only when computer is on. It is temporary memory of computer. The types of RAM are SRAM and DRAM.

b. ROM: it refers to read only memory. It is manufactured by company while design it. The different types of ROM are PROM, EPROM, and EEPROM.

23.

An output is the required final result computed by the processor and through the output devices for the particular sets of inputs through the input devices.

Differences between CRT and LCD monitors are as follows:

1. CRT's are big and bulky while LCD's are thin and light.
2. CRT's consume more power compared to LCDs
3. A by-product of the power consumption, CRTs also get much hotter compared to LCDs
4. LCDs have a greater response time than CRTs
5. LCDs are considerably more expensive than CRTs
6. LCDs have more application than CRTs
7. LCDs can suffer from dead pixels while CRTs do not.

24.

Memory is a storage device of computer that stores any types of data and information.

The types of memory in a computer system are:

1. Cache memory: A CPU cache is a cache used by the central processing unit (CPU) of a computer to reduce the average time to access data from the main memory. The cache is a smaller, faster memory which stores copies of the data from frequently used main memory locations. Most CPUs have different independent caches, including instruction and data caches, where the data cache is usually organized as a hierarchy of more cache levels (L1, L2 etc.)

2. Primary memory: Primary storage, also known as main storage or memory, is the area in a computer in which data is stored for quick access by the computer's processor. The terms random access memory (RAM) and memory are often as synonyms for primary or main storage.

3. Secondary memory: Secondary memory or external memory is used to store a large amount of data at lesser cost per byte than primary memory. They are two orders of magnitude less expensive than primary storage. In addition, secondary storage does not lose the data when the device is powered down. It is non-volatile. Another difference from primary storage in that it is not directly accessible by the CPU, they are accessed via the input/output channels. The most common form of auxiliary memory devices used in consumer systems is flash memory, optical discs, and magnetic disks.

25.

a.

An LCD monitor is a thin, light computer monitor that displays images through the use of a liquid crystal display. LCD screens are found in most laptop computers as well as in flat panel monitors, and have replaced traditional cathode ray tube (CRT) monitors for many users. CRTs once were preferred by many users for their superior color presentation; improvements in LCDs have made the difference less noticeable, but still important to graphics and photography professionals and serious amateurs.

b.

A CRT monitor contains millions of tiny red, green, and blue phosphor dots that glow when struck by an electron beam that travels across the screen to create a visible image. The illustration below shows how this works inside a CRT.

c.

A device that controls the movement of the cursor or pointer on a display screen. A mouse is a small object you can roll along a hard, flat surface. Its name is derived from its shape, which looks a bit like a mouse, its connecting wire that one can imagine to be the mouse's tail, and the fact that one must make it scurry along a surface. As you move the mouse, the pointer on the display screen moves in the same direction. Mice contain at least one button and sometimes as many as three, which have different functions depending on what program is running. Some newer mice also include a scroll wheel for scrolling through long documents.

d.

A keyboard is the set of typewriter-like keys that enables you to enter data into a computer. Computer keyboards are similar to electric-typewriter keyboards but contain additional keys. The keys on computer keyboards are often classified as follows:

alphanumeric keys -- letters and numbers

punctuation keys -- comma, period, semicolon, and so on.

special keys -- function keys, control keys, arrow keys, Caps Lock key, and so on.

e.

Magnetic ink character recognition (MICR) is a character-recognition technology used mainly by the banking industry to ease the processing and clearance of cheques and other documents. The MICR encoding called the MICR line, is at the bottom of cheques and other vouchers and typically includes the document-type indicator, bank code, bank account number, cheque number, cheque amount, and a control indicator. The technology allows MICR readers to scan and read the information directly into a data-collection device. Unlike barcodes and similar technologies, MICR characters can be read easily by humans.

f.

A scanner is a device that captures images from photographic prints, posters, magazine pages, and similar sources for computer editing and display. Scanners come in hand-held, feed-in, and flatbed types and for scanning black-and-white only, or color. Very high resolution scanners are used for scanning for high-resolution printing, but lower resolution scanners are adequate for capturing images for computer display. Scanners usually come with software, such as Adobe's Photoshop product, that lets you resize and otherwise modify a captured image.

g.

It can be defines as an input device that utilizes a light-sensitive detector to select objects on a display screen. A light pen is similar to a mouse, except that with a light pen you can move the pointer and select objects on the display screen by directly pointing to the objects with the pen.

h.

Compiler: A compiler is a piece of code that translates the high level language into machine language. When a user writes a code in a high level language such as Java and wants it to execute, a specific compiler which is designed for Java is used before it will be executed. The compiler scans the entire program first and then translates it into machine code which will be executed by the computer processor and the corresponding tasks will be performed.

Interpreter: Interpreters are not much different than compilers. They also convert the high level language into machine readable binary equivalents. Each time when an interpreter gets a high level language code to be executed, it converts the code into an intermediate code before converting it into the machine code. Each part of the code is interpreted and then execute separately in a sequence and an error is found in a part of the code it will stop the interpretation of the code without translating the next set of the codes.

i.

Optical character recognition, usually abbreviated to OCR, is the mechanical or electronic conversion of scanned or photographed images of typewritten or printed text into machine-encoded/computer-readable text. It is widely used as a form of data entry from some sort of original paper data source, whether passport documents, invoices, bank statement, receipts, business card, mail, or any number of printed records. It is a common method of digitizing printed texts so that they can be electronically edited, searched, stored more compactly, displayed on-line, and used in machine processes such as machine translation, text-to-speech, key data extraction and text mining. OCR is a field of research in pattern recognition, artificial intelligence and computer vision.

j.

The cache is a small amount of high-speed memory, usually with a memory cycle time comparable to the time required by the CPU to fetch one instruction. The cache is usually filled from main memory when instructions or data are fetched into the CPU. Often the main memory will supply a wider data word to the cache than the CPU requires, to fill the cache more rapidly. The amount of information which is replaces at one time in the cache is called the line size for the cache.

k.

Parallel ports are easy to program and faster compared to the serial ports. But main disadvantage is it needs more number of transmission lines. Because of this reason parallel ports are not used in long distance communications. Let us know the basic difference between working of parallel port and serial port. In serial ports, there will be two data lines: One transmission and one receive line. To send a data in serial port, it has to be sent one bit after another with some extra bits like start bit, stop bit and parity bit to detect errors. But in parallel port, all the 8 bits of a byte will be sent to the port at a time and a indication will be sent in another line. There will be some data lines, some control and some handshaking lines in parallel port. If three bytes of data 01000101 10011100 10110011 is to be sent