Differences Between Primary And Secondary Storag Computer Science Essay

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Primary storage is also known as Immediate Access Storage) and is where data is stored on the main computer memory. An example of primary storage is RAM (Random Access Memory - otherwise referred to as RWM (Read Write Memory). RAM is the memory chip stored within the computers motherboard, where data can be read, stored and edited. RAM is extremely fast and is where programs are usually installed, due to its ability to run programs quickly and more efficiently than Secondary storage facilities.

Secondary storage is where software and some documents or spreadsheets are stored onto a hard drive or externally onto a device such as a disk, which is easily accessible when required, via any computer or laptop and easily transportable. This is a much slower form of storage but popularly used, as the computers CPU (Central Processing Unit) memory is limited in size and its storage capacity. The information is usually stored on CD ROM; external hard drives; flash memory or USB Pen drives. Secondary storage is permanent and only becomes obsolete in time (when it eventually wears out or is replaced by new and improved technology). "Complex functions such as translators for high-level languages and operating systems are placed on ROM memory". (Comp Wisdom, 2006). The ROM memory chip is a viable permanent storage facility for manufacturers, as users are unable to overwrite the information stored on this device. Off-site data storage is non-volatile and is where information is stored at another location away from the computer, which is accessible from a direct call or via the internet. Off-site data storage is beneficial as a backup if complications arise with the onsite computer system. (No-Moa Publishers, 2000)

Table 1-Differences between Primary and Secondary Storage. (Integrated Publishing, 2010)



Volatile - Temporary

Non-Volatile - Permanent

Fast memory therefore expensive

Slow memory therefore cheaper

Smaller storage capacity (L2 Cache = 2MB)

Larger storage capacity

Closer to CPU or internal so faster

Connects to the CPU so slower performance


PROM - Programmable Read Only Memory, already programmed by the manufacturer, non-editable. Needs a device to burn to disk and if mistake made cannot be corrected.

EPROM - Electronically Programmable Read Only Memory. Holds data no power supply, electrically reprogrammed up to 100 times. Stores Calibration data in real time clocks.

Other types: DRAM,SRAM, MRAM

Other types: ROM - cane be read but not overwritten

Hard drive, CD's, DVD's, Flash Memory, Magnetic tapes, Offline storage, EEPROM.

Figure 1 - Image of Primary and Secondary Storage.

2. Virtualization (or hypervisor) is similar to simulation where an identical copy of an operating system is made.Virtualization can be formed for various systems such as: Networks; Platforms; Applications; Desktops; servers and storage devices. This means that multiple virtual machines can be run on a single host (via virtualization),containing its own resources; operating systems and hardware, reducing the risk of software applications from causing complications with each other due to incompatibility errors or conflict.

This functionality has also been developed for wireless technology including mobile phones. The benefit of mobile phones having this functionality is that the "virtualized environment…would be open to developers or open to the user to add and install applications to customize the phone as they want"… without "disrupting the carrier network".(Hazelton, Nov 2008).

Figure 2: Virtualization Image - Blue Whale Web Inc, 2010

3. The Home Theater receiver, also referred to as an AV receiver or Surround Sound Receiver, is the heart of a home theater system and provides most, if not all, the inputs and outputs that you connect everything, including your television, into. An AV Receiver provides an easy and cost-effective way of centralizing your your home theater system. Part One discusses the audio factors to take into consideration.

4. The cloud in network systems is an abstraction of the real system and itscomplex infrastructure. It hides the actual processes and network connections to the user such as servers, routers hubs, switches, cabling and storage (the points of entry and exits) that enable data processing.(Wiley Publishing Incoporated, 1998)The cloud represents the communications network such as network cables, which connect to various devices in order to communicate over short distances or over a large geographical area, similar to that of a telephone infrastructure.

5a. PDF known as Portable Document Formatis a system by which files can be displayed on various applications which is "independent of …software, hardware and operating systems" which they originated from and the computer or printer from which the output originated.(Adobe Systems Incorporated, 2006, p. 33). PDF files have a sophisticated imaging model derived from' PostScript page description language' (Adobe Systems Incorporated, 2006)which has been redefined to incorporate binary format.PDF files contain universally accepted format of arrays; syntaxes; graphics; imagery and text containing specified instructions objects that allows outputto be consistent across un-similar devices.

b. The format for storing, page layout and managing objects is compressed in PDF files via means of fixed, two-dimensional PostScript document.The advantages of using PDF files rather than HTML are:-

Files can be encrypted and cannot be tampered with; can have a digital signature which can be for legal issues; images and information can be used as evidence in court, whereas HTML has no security controls.

PDF have a low risk of being contaminated by a virus.

A PDF file can be password encrypted.

PDF reader software which is free of charge whereas HTML requires a Browser window.

Font is embedded in a PDF file ensuring that layout and appearance remains intact, whereas HTML font and appearance is defined by the creator which can appear differently depending on browser functionality used.

PDF is designed to take appearance of documentation into consideration, whereas HTML concentrates on structure.

PDF files hold large data compared to that of HTML.(Adobe Systems Incorporated, 2006)

c. PDF has a font embedded system allowing font programsto travel with the document, which are interpreted at the destination by the data structure, which is built into the application or by means of an external font file. This transfers the information into a character which is a graphical shape known as a glyph. The file compresses information which preserves data and maintains the "integrity "of the original document including its fonts and graphics. (Chuck Geschke, 2004, p. 24)

d. A PDF contains 5 object types in relation to graphics, which are embedded into the file and transported with the document these being:-





These objects define the position, orientation, size of text, graphics and bitmap imagery that appear on the page by means of appropriate shading, structure, syntax, colour fill and line strokes. The cleverly designed graphical parameters allow conversion and compression files to make certain discreet changes to the graphics without changing the surrounding environment.The filedetermines the imagery and displays it in the exact layout and position. This is known as the Cartesian co-ordinate system. (Adobe Incorporated, 2006)

A vector (object) image is handled similarly, as paths are made up of lines called "Bezier curves". (Adobe Systems Incorporated, 2006)The path object transfers these into paths that can be stroked and filled. The output format is then transferred with the file to cater for the imagery.

e. There are a number of limitations that a PDF has on the end user these being:-

Graphic recognition is time consuming to process documents containing Vector graphics

Documents holding certain layouts like magazines and newspapers cannot be deciphered correctly.

The documents are un-editable which could affect documents pertaining to lawyers, that require proofreading and alterations by the client.

Due to new versions being released on a regular basis with new functionality, causes incompatibilities with documents created by earlier versions.

Converting a PDF file back into a formatted word document asPDF does not recognise "paragraphs, formatting, headers, footers, indentations, and line breaks'. (PDF Tools, 2005)

6. A computer network is divided physically as well as logically. A collision domain (Ethernet segment) is where two or more devices are attempting to transmit packets of data at the same time and are usually contained within a broadcast domain. Devices that are attached to a hub or a switch are within a collision domain. Collision domains are usually divided by a switch or bridgesand use a collision -sensing protocol called CSMA/CD. The basic strategy for this protocol is it detects imminent collisions by abnormalities in the voltage, which occurs in the computer rejecting the corrupted frame (runt). (CISCO, 2006)

A broadcast domain (Ethernet LAN) is a logical part of the network that emits data to another device.(Symatech, 2010)

Figure 3 - This diagram shows the 2Broadcast domains in Green and the 5collision domains in Red.

Table 2 - This table shows the ISO-OSI layers and the domains.


ISO-OSI Layers

What's processed




Application Layer

Ports, sockets



Presentation Layer

Format, encoding



Session Layer

Messages, communication

Controls Dialogue


Transport Layer

TCP segment

Data transfer


Network Layer

IP Packet, IP Address

Broadcast domains. Layer 3 devices stop the flow of broadcast domains

IP address, Router, level 3 switch


Data Link Layer

Frame, Interface cards, adapters

Single separated Collision, one single broadcast domain also created. Layer two network devices can divide collision domains.

Switches, Bridges


Physical Layer

Bit Stream

Single Broadcast and Collision

HUB, Repeaters

7. Von Neumann's architecture comprises of the four main components,see diagram below. This is used in current computers lay the foundation to what is known as the 'Little Man Computer'(Englander, 2010)the essential criteria for this architecture is the memory which has a 'stored program concept' (Englander, 2010) which allows the programs to be edited. It stores the address in a sequenced address order which has its own memory slot and traced by unique location number.

Memory- consists of RAM to store programs and data

Control unit is used to fetch information from memory and decodes it and performs operations to complete the task

Arithmetic unit - performs mathematical calculations

Input/output is the interface with the human operator

Figure 4- diagram of Von Neumann's Computer Architecture


An example of entering and adding two numbers is as follows:

Take first number and input (the number is now stored in the calculator)

store the number (this is stored in memory slot and number is left on calculator)

-Input second number (2nd number replace first in calculator)

Add first number to second (fetch 1st number from stored address location and add to number in calculator)

Display/output result

8. 32 bitswide or 4 Bytes can address 4Gigabytes of memory = 4 (232 = 4,294,967,296). AMD introduced the first 32 bit flash memory device on 5th August 2001 which would allow systems to run 8 x faster than those using standard flash memory. (Advanced Micro Devices Incorporated, 2010).

9. Volatile memory is a term derived from the Latin word "volatilis" which translated means "to fly". This terminology is applied to something that is unpredictable; subject to change; unstable or hostile. The RAM (Random Access Memory) in a computer istemporary (volatile storage), as the information stored is obliterated when the power is either switched off or interrupted, as power is required to retain information stored on the machines memory.

Non Volatile memory (NVRAM) is not deleted when the connection between the memory and the CPU (Central Processing Unit) is lost. Devices such as memory disks or hard disk drives store information permanently until it is no longer required by the user.

RAM, DRAM, SRAM are all forms of volatile memory and ROM and Flash memory are non-volatile forms of memory. Flash memory is widely used in the Automobile manufacturing industries, for car applications to work efficiently. Some cars contain MCU's chips (Microcontrollers), where program functionality are stored using non-volatile memory on the MCU, allowingcar functionality to work correctly such as Cruise control, air bag safety mechanism, engine controls and temperatures.(International Engineering Consortium, 2006)It could be crucial if this information plus vital safety checks were erased every time avehicle is switched off!

10. Figure 5 - Data Flow Diagram showing Mixed number in a base other than 10 converted to a Decimal. (Englander, Number Systems, 2010)

Display Answer

Display Integer and Decimal parts together

Convert Fractional Part to base 10

Convert Integer part to decimal

Split into Integer number and Fractional parts

Start with

Mixed number

Mixed Number = whole number + fraction

Another way to convert a mixed number into a decimal is as follows:-

Answer =


Round answer to two decimal places



To get Decimal - Divide numerator by denominator

Rewrite improper fraction with numerator on top

8 x 2 x 7

Turn mixed number into improper fraction

2 7/8

Start with

Mixed number

Mixed Number = whole number + fraction