Computer aided electronic design


Yascom, a multinational company based in London specialises in computer aided electronic design and are also manufacturers and designers of printed circuit boards (PCB).

        The company should design and manufacture computer aided electronics and also design different computer softwares and their should not be any duplication in certain department of the internet. Their should also be video conferencing. So that they could exchange ideas in certain areas of business like sharing design ideas. As the company is not sure of security requirements they will also require a policy.


Main Components of computer system

1) CPU (Central Processing Unit)

The processor of the computer is CPU. It does most of the processing in computer. Now a days there are different types of CPU's in market and most of it's manufacturers are Intel or AMD. CPU's vary for laptop, desktop, portable computers, servers and mobile devices .Earlier the CPU were large but as the improvement in technology made it microprocessor. Dual core CPU and quad core CPU are now available in market. Dual core CPU consist of two separate processors and quad core CPU consist of 4 separate processors. In future there will be CPU's with more cores which will provide it with more speed. The speed of the CPU is measured megahertz or gigahertz. The measurement of processing speed of CPU is called CPU clock speed. The higher the CPU clock speed the more will be instructions processed per second. There are some other factors that affect the speed of the CPU like memory, bus speed ,Ram etc.

The CPU consist of following components

  • Arithmetic Logic Unit(ALU)
  • It carries out the Arithmetic operations like addition, subtraction and logical actions.

  • Floating Point Unit(FPU)
  • It carries out the operations like decimal addition and subtraction.

  • Control Unit
  • The control unit directs and co-ordinates the activities of the entire computer.

  • Prefetch Unit
  • It is a small part of memory that holds the next instruction and also compares to the content of the cache and RAM.

  • Decode Unit
  • As the name says it decodes or translate the instructions .So that these instructions can be understood by the ALU,FPU and Control unit.

  • Internal cache and Registers
  • Store data and instructions for the CPU

  • Bus interface Unit
  • It helps the core to communicate with the CPU components.

How the CPU works?

A computer program is executed by a CPU in associated with the memory unit. Only one instruction can be executed at a time by a CPU even though it feels like many instruction are executed at a time. Most of the PCs generally execute an instruction in less than one millionth of a second.

When an instruction or command is made by the user, the program instruction and data should be stored into the memory from the input device (keyboard, Joystick, Scanner) before the program execution. After all the necessary instructions are placed in the memory, the CPU starts performing the step for data execution

  1. The control unit fetches the information from the memory
  2. The instruction is decoded in the control unit and moved to the ALU along with the rest of the data from the memory for further calculations.
  3. These two steps are together known as Instruction time.

  4. The arithmetic or logical instructions are executed in the ALU .That is the actual operation on data and its control are given to the ALU
  5. The result of the process is stored in the memory in a register by the ALU Step 3 and 4 together is known as Executed time.

The result is released to an output device or a secondary storage device from the memory directed by the control unit. This whole process, Combination of Instruction time and Execution time as a Machine Cycle.

In each of the CPU there is an internal clock which produces pulses at a fixed rate to synchronize all computer operations. Each CPU is designed to understand and perform computations on a specific group of instructions called instruction set.

2) RAM (Random Access Memory)

There are two types of memory primary memory and secondary memory. Random Access Memory is primary memory. The primary memory is otherwise called main memory. The Random Access Memory is volatile in nature and the user programs and data are stored in this part of the main memory. It implicates that it possible to read from and write to any location within RAM by specifying its location or address. New data can be written onto any location, however, while doing so the previous data will be erased.

The main memory is used as a:

  1. Storage of a copy of the main software program that controls the general operation of the computer.
  2. Temporary storage of a copy of application program instructions to be retrieved by the CPU.
  3. Temporary storage of a data that have been input from the input devices.
  4. Temporary storage of result that have been produced as a result of processing.

RAM is plugged onto the motherboard as an array of chips on a circuit board known as memory module. In order to process the computer programs fast enough, adequate RAM is needed. RAM may be classified into Dynamic RAM and Static RAM. The non volatile RAM is under development like M RAM and P RAM.


A hard disk is composed of one or more rigid platters that are mounted on a common spindle. Both sides of these platters are coated with magnetisable material and both these sides are recordable. The platters and spindle in the disks are together called disk pack.

Disk drive is used for reading and writing information from a disk. The reading and writing is performed through special read/write head attached to the drive. The read /write head does not actually touch the recording surface of the disk platters. The tiny space between read/write head and platters is called fly hight.

Two types of read/write mechanisms are used

  1. Fixed head
  2. Moving head

        In a fixed head system the read/write head is not movable. Therefore a number of read/write heads are used for each plates.

        In moving head system , the read/write head is movable. Therefore only one read/write head is used for each plate. In this type read/write head moves horizontally across the surface of the disk plate. Each plate has two surface , namely, upper surface and lower surface.

The surface of the disk is divided into concentric circles called tracks. Sometimes these tracks are divided into number of parts called sectors, that is sector is one portion of track. A set of similar tracks on all surfaces is called a cylinder.

To perform read/write operation, first find the cylinder ,then find the surface number and find the sector number of a specified record. This is called sector addressing. For example, if a record is located in the address 1163, then the cylinder is 11, surface number is 6 and sector is 3. After getting the actual address the read/write head read or write the specified record at that location. Quality of disk is specified by capacity and access time of that disk. Capacity refers to the number of bytes that can be stored in a disk and specified in KB or MB or GB.

Access time is the time taken to locate a particular record on a disk and transfer it to the Central Processing Unit. Access time can be divided into five components.

Access time = Read/write head selection time + Access arm movement time + Seek time + Rotational delay + Data transfer time

Read/write selection time: The amount of time required to select particular read/write head.

Access arm movement time: The amount of time required to move the head to select the proper cylinder.

Seek time: The amount of time required to position the head on a selected track.

Rotational delay: The amount of time that passes while system is locating for the proper records or sector to spin under selected read/write head.

Data transfer time: The amount of time taken to transfer data from disk to CPU.

The most popular type of hard disk in use is Winchester disk . Winchester disk is a special type of hard disk in which both the disk platters and disk drives are sealed in a contamination free containers. One of the major advantages of Winchester disk is that disk plates are interchangeable on their drives.


  1. Large storage capacity
  2. Direct access storage
  3. Reusable medium
  4. Data transfer speed is very high
  5. Number of files can be stored in same disk plates.


  1. More costly than tape
  2. Not human readable
  3. Chances of disk crash is more when the disk is affected by dust.

4) BUS

In computing terms, the data transfer between the components in a computer or between two or more computers is through a component known as BUS. In early computer systems, the buses are just parallel electrical buses whereas in modern computers buses are both parallel and bit-serial which is either in multi-drop or daisy chain topology. These topologies are connected using switched hubs.

There are two types of buses, parallel buses and serial buses. In a parallel bus, the data are carried in parallel order on multiple wires where as in serial bus; bit serial form is applied to carry the data from one component to the other.

In almost every computer systems there are internal and external buses. All the internal components of a computer are connected to the motherboard through internal buses. The internal buses are also known as local buses. External buses are used to connect the external peripherals to the motherboard.

Address Bus

The physical address within a computer system is specified by the address bus in the computer. The address bus is used when the microprocessor need to read or write to a specified memory location, the microprocessor specifies the location of the memory on the address bus where the data send through the data bus has to be written to or read from. The amount of memory a system can address is determined by the width of the address bus. For instance, a microprocessor with 64-bit address bus can address 264 locations of memory.

Control Bus

The control bus is used to communicate the internal devices by the CPU within a computer system. The address bus carries the address location of the device which the microprocessor is communicating with, meanwhile the data bus carries the original data that have to be processed by the CPU and the control bus carries the commands from the CPU.

Front side Bus

The front side bus is used to connect the CPU with other components and the main memory within a computer. The speed of the FSB ranges from 66MHz to 400MHz. The Front Side Bus is also known as Processor bus, Memory Bus or System Bus.

Back Side Bus

The connection between the CPU and L2 Cache is done by the back side bus (BSB). BSB was introduced by Intel Pentium Pro and the speed of the BSB depends on the processor speed.

Expansion Bus

The Expansion BUS is used to connect the input and output devices of computer.

PCI and PCI Express Bus

This is used to interconnecting memory cards, chips and expansion cards.

Universal Serial Bus

The Universal Serial Bus is allows easy connection of input and output devices and high speed. When plugged in everything done in automatically.

Firewire/IEEE 1394 Bus

This bus is used to connect the input and output devices of computer.


Keyboard is an online data entry device. The most common type of input device used for rapidly entering data into the computer is keyboard. A keyboard is used to enter the data into a computer and is similar to the keyboard of a type writer. It contains numbers, letters and some special characters like +,-,$,",&,%, etc. In addition to these keys, it also contains some special purpose keys.

Keys in Keyboard

Enter/Return Key: Used to alert your system that you have finished supplying instruction. In word processing program, pressing Enter key begins a new paragraph or a new line.

Function Key: Functions of these keys are expanded on software we used.

Typewriter Key: These keys are used to enter alphabets, Punctuations etc.

Cursor controlling: These keys are used for moving the cursor to different positions on the screen. Cursor control keys include arrow keys ,Page Up, Page Down, Home, and End keys. Page up key is used to move to the previous screen or page and Page Down key is used to move to the next screen or page. Home key is used to move cursor to top of the document of beginning of the line and End key is used to move cursor to the end of the line.

Combination Keys: Ctrl, Alt, Shift are called combination keys because these keys are used with other keys. Functions of these keys depend on the software we use.

Esc: Used to cancel the entry or operation.

Delete: Used to delete characters in the current position.

Backspace: It erases the character to the left and moves the cursor one position back.

Numeric Keypad: The rightmost part of the keyboard is called numeric keypad because it looks like keys of a calculator. All arithmetical operations are done by using the keys in this pad.

Caps lock Key: Used to on or off the caps lock facility.

Computer keyboards can be classified based on the number of keys and the method of data transfer. Based on the number of keys on the keyboard, it is classified into

  1. Standard Keyboard
  2. Enhanced Keyboard

On the other hand, based on the method of data transfer, keyboards can be classified into

  1. I. Serial Keyboard
  2. II. Parallel Keyboard

A keyboard which contains 83-86 keys, is called Standard keyboard. A keyboard which contains more than 100 keys is called Enhanced keyboard. A serial keyboard sends data in a serial fashion and parallel keyboard sends bits of data in separate lines simultaneously.

When you press a key more than one time, that character will be repeatedly displayed on the monitor. This is called typematic.

How the Keys work?

A key in keyboard contain two contacts are usually separated by a space.

When the key pressed, the contacts touch each other and current goes through it and the processor inside the keyboard detect the key press and send corresponding code called scan code to the system.


The most popular output device that is used for direct access processing is the visual display unit or monitor. It consists a Cathode Ray tube (CRT) screen which displays the characters. This device is popular as it is not very expensive, easy to operate and the input and output can be seen on the screen. The size of the screen varies from 8" to 20" and can display 20 to 30 lines. The number of characters per line varies from 40 to 120. The set of characters that can be displayed on the screen are alphabets- both upper and lower cases, numbers and special characters. The screen displays an indicator known as cursor. The position of cursor indicates the position where the next character will be displayed on the screen.

A CRT monitor is a high precision piece of equipment. In the back of a monitor housing there is an electron gun. The gun shoots a beam of electron through a magnetic coil, which aims the beam at the front of monitor. The back of monitor screen is coated with phosphor. The phosphor is a chemical that glows when it is exposed to the beam. The screen's phosphor coating is organized into a grid of dots called pixels. Actually the electron gun does not just focus on a spot and shoot electrons there. It systematically aims at every dot of phosphor on the screen, starting at the top left corner and scanning to the right edge, then dropping down a tiny distance and scanning another line, like eyes reading the letters on a page. As the electron gun scans, the circuitry driving the monitor will adjust the intensity of each beam to determine how bright each pixel glows.

Display monitors used for graphics are called dot-addressable displays or bit-mapped displays. In these monitors, the number of addressable location on the screen is equal to the number of dots that can be illuminated on the screen. Each dot that can be illuminated is called a picture element or pixel. In bit- mapped displays the resolution of the characters on the screen goes on improving with the number of pixels.

There are two types of monitors. They are Monochrome Monitors and Colour Monitors. Monochrome monitors are used with personal computers or used as terminals. These units display the characters in white or green colour on a black background. They are suitable for alphanumeric applications such as Word processing.

Colour monitors are mostly used with mini computers or large computers. The colour monitors are dot-addressable displays. There are two types of colour monitors - Composite video monitors and RBG monitors. Both monitors can be used for colour graphics.

A colour monitor works just like a monochrome monitor, except that there are three electron guns instead of one. These guns represent the primary additive colours. Different colour can be displayed by combining various intensities of these coloured beams. The quality of image that a monitor can display is defined more by the capabilities of another device called the video controller.

The video controller is an intermediate device between CPU and monitor. The controller contains the memory and other circuitry necessary to send information to the monitor for display on the screen. The video controller uses its own special memory to maintain the image that is received from the CPU and sends to the monitor.

LCD (Liquid Crystal Display)

Liquid Crystal Displays are commonly used in small system, such as calculators and laptops. Now a day's most of the monitor is LCD. The LCD is made up of a special kind of liquid crystal placed between two plates. The top plate is transparent and bottom one is reflective. The liquid crystal is normally transparent and the bottom plate reflects the light that passes through it. When charged electrically the crystal becomes opaque end blocks the light.


  1. Power consumption is very less.
  2. Small in size.
  3. Better portability.
  4. It produces high quality output.


A computer is made up of integrated components (input and output devices, storage, CPU) that work together to perform the steps in the program being executed. The input or output units cannot function until they receive signals from CPU. Similarly the storage unit or the CPU alone is no use. So the usefulness of each unit depends on other units and can be realized only when all the units are put together to form a system. So each and every single integrated components is important for a system and also the performance of the system is depend these components.


An Operating System is a set of programs that control the operations of CPU and enables user to communicate with the system. Varieties of operating systems are available in market. Operating systems are mostly stored on disk and transferred into CPU only when it is needed.

Functions of Operating System

  1. Providing user interface.
  2. Running programs
  3. Sharing information's
  4. Managing Hardware
  5. Processing interrupt
  6. Working with device drivers

1. Providing user interface

When we work with a computer we can see a set of items on the screen. These items are called user interface.

E.g.; Recycle bin ,Internet explorer

Two most kind of user interfaces are graphical user interface (GUI) and command line interface/Character User interface (CUI)/Test user interface (TUI).

Most modern Operating Systems are Graphical User Interface. We can control a Graphical User Interface based system by clicking graphical object on the screen. In a typical Graphical User Interface all objects and resources appear on a background called desktop.

In Graphical User Interface we can access programs and other resources in rectangular frame called Windows. Application running under the same Operating System use many of the same graphical elements, so we can see a familiar interface no matter what program we are using .some older Os use a Character User Interface which the user control by typing at a prompt.

E.g.: MS DOS

2. Running programs

The Operating System providing consistent interface between application programs and the user. It also interface between those programs and other computer resources, such as memory, printer etc.

Programmers write computer program with built in instruction called system calls. They request serves from the program.

E.g.: If we want to retrieve a file we use the open dialogue box to list the program calls on the Operating System. The Operating System goes to the same process to built a list of files.

3 Sharing information

Many type of applications provide to move blocks of data from one place to another.

For e.g.; if we want to copy a chart from Excel to Word processor, we can select the copy command and then apply the paste command .Thus the OS provide the data movement facilities.

4. Managing hardware

When programs run they need to use the computer's memory, monitor, disk drives and printer. The Operating System is the intermediary between programs and the hardware. In a computer network the Operating System also mediate between our computer and other devices on the network.

5. Processing interrupt

The Operating System response to request to use memory and other devices, keeps track of which program have access to devices and co-ordinate everything the hardware done. So that various activities do not overlap. The Operating System uses interrupt request (IRQS) to help CPU coordinate the process.

6. Working with device drivers

The Operating System provides programs for working with special devices such as printers. These programs are called drivers. Because they allow the Operating System and other programs to activate and use drive is a hardware device. Most new software in work with our printer, monitor and other equipment without requiring to install any special drivers.



To overcome the limitations of DOS, Microsoft has developed a new graphical based operating system called windows. It is the worlds most popular operating system. Its main objectives are to provide an easier way for a user to work with PC.

Characteristics of Windows

  1. It is a graphical user interface based Operating System
  2. IT is very easy to use
  3. it support long file name
  4. It gives multimedia technology such as audio, video, textual, graphical tools on a single platform
  5. It incorporate graphs, charts music, video clipart and so on.

Different versions of Windows operating systems are available, such as windows 2.1/3.1, Windows 95, Windows 98, and Windows 2000 etc. Windows 3.1 was the predecessor of Windows 95. The basic difference between Windows 3.X when compared to Windows 95 was that it required DOS to be installed, whereas Windows 95 has DOS integrated within it. Of course there are several major improvements in Windows 95 as compared to Windows 3.X. Windows is named so because you can work on several Windows at the same time.

Windows 3.0 was released in 1990. Windows 3.0 was the operating environment that convinced people to switch from DOS based program to native Windows program. Windows 3.1 was released in 1992. The operating system was more stable in the version, which also included multimedia support. In the same year Windows for workgroups 3.1 and 3.11 were released. These versions had added Microsoft mail and better networking integration, to the existing one.

Microsoft knew that an entirely new and to provide better multi tasking and network facility, Windows NT 3.1 was first released in 1993. Work on Windows 95 was started in 1992 and it came into the market in August 1995. Windows 95 incorporated many features of Windows 3.X family as well as the features from the Windows NT family, Windows 95 continues to be the most popular operating system for many reasons such as its ease of use, low hardware requirement etc.

In Windows 98, Windows 95 uses a similar graphical user interface of Windows 3.X. Windows ME is used for home based computers and which is allows home networking and shared networking. Windows NT replaces to come an another operating system called Windows 2000. This operating system is mostly used for servers and business workstations and which is support for wireless devices. Then the Windows 2000 and Windows ME replaced to come a new operating system called Windows XP. In this version Microsoft improved the capabilities like photo, video and music editing, network etc. And this operating system has a large number of users.

Later Microsoft was release Windows Vista. Windows 7 is the latest operating system among the Windows family. In the case of Windows vista Microsoft included the features like animation, live thumbnails, instant search, sidebar etc. And in this operating system Microsoft improved multimedia, networking and hardware requirements. Windows 7 is the new version of Windows released on 2009. This operating system is faster than Vista. And this operating system is improved home networking capabilities. And which is included the features like gadgets and jump lists etc. The server version of Windows is called Windows server. 2008 is the most recent version of Windows server.


Linux is an operating system for Intel based PCs. The system has been designed and builds by hundreds of programmers scattered around the world. LINUX was developed in the early 1990's by Linux Torvald along with other programmers around the world.

As an operating system, it performs many of the same functions as DOS or Windows. However LINUX is distinguished by its power and flexibility. It is free. Unlike the official operating system, LINUX is distributed freely. LINUX also comes with source code, so you can change or customise the software to adapt your own needs.

LINUX is a great operating system that is rich in features adapted from other versions of UNIX. It is a powerful UNIX like Operating System. It is a fast growing Operating System .LINUX enhance the PC on which the titanic movies animations where created. It includes all UNIX features such as multitasking multiprocessor support Internet support Graphical user interface. It is a full 32 bit, 64 bit multitasking OS that support multiple users and multiple processors. LINUX can run on any computer and can support any kind of application. LINUX uses a command line interface, and also windows base Graphical User Interface environment.

The main non technical difference between LINUX and UNIX is its price. It is a freeware Operating System. The most popular LINUX vendors are Redhat and Noreil. Both offer special LINUX bundles for desktop computers as well as for servers. For all these reasons, LINUX has become a popular OS. Students and teachers have flocked to LINUX to participate in the global community that has built up around the Operating System .This community invites LINUX users and developers to contribute modifications and enhancement, and it freely share information about UNIX and LINUX related issues. LINUX is mostly used with severs, personal computers and super computers. This operating system is less expensive than Windows.

        I recommend the operating system LINUX. Because this operating system uses a command line interface and also windows base Graphical User Interface environment. So LINUX is best to avoid viruses, spam and spyware. LINUX can run on any computer and can support any kind of application.




Why upgrading?

The two main reasons to upgrade a hard disk is that we need more space for storing applications as well as data or the older disk has crashed and we need to replace i.

A third reason to upgrade is to improve the computers overall performance by using a faster and responsive drive from which to run the operating system and application.

When we need to upgrade?

  1. If we are unable to install a new application. Due to an insufficient disk space memory.
  2. Unusual application shutdown due to reduction in temporary storage space on the hard disk.
  3. Sometimes we have to delete files due to insufficient disk space while running the applications.
  4. If we encounter with disk errors continuously

Upgrading can be done mainly in two ways.

Either install a new one or install another, along with the old one (second hard disk)

Second Hard Disk installation steps:

  1. Buy the necessary cable, power cable etc along with the HDD.
  2. Remove the cover of the machine.
  3. Check the master slave jumper settings:-a secondary hard disk should be set as a slave. Set the jumpers before installing the hard disk.
  4. Connect the signal cable and power cable properly.
  5. Specify the hard disk parameters in CMOS.
  6. Perform the partitioning procedures using FDISK utility.
  7. Format the disk and transfer the files.


Upgrading of the memory can be done either using software tools or by installing faster and higher capacity memory.

Using software tools, already available memory can be made more productive and faster. Software tools include HIMEN.SYS,EMM386.EXE,etc. Microsoft provides these programs.

To install new memory hardware we have to decide about the type and capacity and speed of the memory. Different types of memory could be DIP, SIMM, SIPP, DIMM, memory expansion cards.

Memory upgrading steps:

  1. Turn off the system
  2. Remove the cover of the cabinet
  3. Remove the old memory
  4. Place the new memory card in the slot.

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