Recommendation Of Computer System Yascom Computer Science Essay


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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

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

The control unit fetches the information from the memory

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.

These two steps are together known as Instruction time.

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

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.


There are two types of memory namely primary memory and secondary memory. RAM is primary memory where the OS, all the application programs, and current data are kept so that there can be accessed quickly by the processor. RAM is faster to read from and write to than hard disk or floppy disk. RAM is plugged onto the motherboard as an array of chips on a circuit board known as memory module. In order to read the computer programs fast enough, adequate RAM is needed. RAM is known as volatile memory as it store all the information and data till the PC is shutdown. SD RAM is most popularly used in PCs. RAM may be classified into Dynamic RAM and Static RAM.

Static RAM

Static RAM is a semiconductor memory. S RAM does not require periodic refreshing or rewriting like the traditional D RAM as S RAM keeps all the data as long as power is plugged in to keep it charged. The S RAM is composed of flip flop circuitry that does not require refreshing.

The flip flop circuitry is made up of 4 to 6 transistors that unfortunately makes S RAM large in size, fast but expensive. As a result static RAM is used to manufacture the high-speed sensitive cache of a computer's microprocessor.

Types of Static RAM

Non Volatile S RAM

Standard S RAM functionally is used in a non-volatile S RAM. These S RAM s have the capability to save the data and information even after the system is shutdown.

Asynchronous S RAM

These S RAM s range from 4 Kb to 32 Mb. Due to the high speed access time, these S RAM s are used as main memory in some cache less


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

Fixed head

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.


Large storage capacity

Direct access storage

Reusable medium

Data transfer speed is very high

Number of files can be stored in same disk plates.


More costly than tape

Not human readable

Chances of disk crash is more when the disk is affected by dust.


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

Standard Keyboard

Enhanced Keyboard

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

Serial Keyboard

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 circuitory 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 circuitory 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.


Liquid Crystal Displays are commonly used in small system, such as calculators and laptops. Now a days 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 reflect the light that passes through it. When charged electrically the crystal becomes opaque end blocks the light.


Power consumption is very less.

Small in size.

Better portability.

It produces high quality output.

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