1. Technical Considerations Information Systems Notes Information Systems Design & Development: Testing, Hardware Requirements, Software Requirements, Storage

2. Contents Hardware Requirements – Processor and Memory Hardware Requirements – Processor and Memory  Questions Questions Device Types and Peripherals  Questions Questions Storage Requirements  Questions Questions Storage Trends, Storage Methods & Backup  Questions Questions Compression  Questions Questions Operating Systems & Software  Questions Questions

3. Hardware Requirements of an Information System Compatible software is able to run on a users system and communicate with the other pieces of software on that system When a new information system is created, it is tested to check that it is compatible with the user’s system. The information system usually has a number of requirements it needs in order to run properly The hardware requirements of an information system refer to the specific requirements on the hardware of the users system – The processor and memory, amongst others

4. Processor requirements The processor is responsible for executing the individual instructions of an information system The processor has two attributes that can be considered when discussing hardware requirements:  Clock Speed  Number of cores The clock speed of a processor determines how fast it can process instructions A faster processor can complete more instructions in the same time frame than a slower processor. This means it can run more complicated programs that still interact with the user in real time. Clock speed is measured in Gigahertz (GHz)

5. Multi-core Processors A multi-core processor is a computer processor that contains two or more independent processing units. Multi-core processors allow multiple instructions from an information system to be executed at the same time, in parallel. This can allow an information system to run faster – for example an internet browser might make use of one core to interpret the HTML of a website, whilst a second core is used to decode the video embedded in it. However, an information system must be specifically written to use multi-threading in order to take advantage of multiple processor cores

6. Memory A computer includes a number of different types of memory – the cache, ROM and RAM. Cache memory is a small sized area of ultra fast access storage located on the processor The cache stores a copy of the information in frequently accessed locations of the main memory. As the cache can be accessed faster, this improves performance Read Only Memory is persistent, non volatile memory, the contents of which cannot be changed Computers usually only have a small amount of ROM. It is typically used to store the bootstrap loader. A small operating system that starts up the computer and starts the larger operating system that runs the computer

7. RAM The random access memory (or RAM) of a computer is used to store the programs it is currently running, and any data they are using. RAM is volatile, but the contents can be changed and it is faster to access than storage. To use an information system, a computer must have enough RAM to accommodate the information system program, as well as the information it contains. Computers with large amounts of RAM can run multiple programs at the same time, enabling multitasking. Additional RAM can be added to a computer in order to improve its performance. However, there is a maximum amount of memory a computer can have based on the processor’s architecture.

8. Questions – Processors & Memory Answer questions in full sentences! 1. What is meant by compatibility? 2. Find out the system requirements for the latest version of Microsoft Office. State whether or not it could be used with laptop below. 3. Explain how the speed of the processor affects what programs it is capable of running. 4. Describe how a multi-core processor can be used to improve the performance of an information system. 5. What is the disadvantage of multi-core processors 6. Explain how cache memory improves system performance 7. Explain what ROM is and describe two of its features 8. Explain what RAM is and describe two of its features 9. Why does adding more RAM improve a computer’s ability to multitask?

9. Device Types & Peripherals The device type of a computer refers whether the computer is a desktop, laptop, tablet, smartphone or other computer device. The different types of computer have different characteristics in terms of their portability and processing power: Information systems are often designed to work on a specific device type. This affects the system requirements of the information system PortableNot Portable Not PowerfulPowerful

10. Peripherals Peripherals are the input and output devices that can be attached to a computer. The input and output devices affect how information can be entered and viewed on an information system The input and output devices of a computer are related to the type of device – smaller devices make use of touch sensitive screens for input whilst larger devices make use of keyboards and mice Some information systems will require the use of specialised input or output devices.

11. Case Study – Stock Control Stock control is an example of an information system used in shops and warehouses. A database is used to track the goods stored in the shop. A specialised input device used with stock control information systems is a barcode reader. The scanner reads the black and white lines of the bar code and inputs the numeric code identifying the product into the information system directly. In some systems this has been replaced with a digital camera and bar code or QR code reader software. Tablet computer devices are used by employees when restocking shelves. This enables them to walk about the store, scanning codes on the shelves and using them to update the database via a wi-fi connection

12. Questions – Device Types and Peripherals Answer questions in full sentences! 1. Describe six input devices that you are familiar with. 2. Describe four output devices that you are familiar with. 3. Describe what a desktop computer is. 4. Describe what a laptop computer is. 5. Describe what a tablet computer is 6. Describe what a smartphone is 7. Find out the specifications of an example of each of the four types of computer in questions 3-6 and record them in the table below: Name/ Type of computer Processor speed Memory / RAM Storage capacity & type Input / Output devices

13. Storage Requirements of an Information System The storage of a computer is used to save data and programs. Storage is persistent, slower to access than memory, but often many times larger in terms of capacity. Information systems have two requirements in terms of storage:  The storage must be large enough to store the information system program  The storage must be large enough to store the data kept by the information system The storage capacity required by the program itself is usually given in the system requirements for the program. The storage required for the information system’s data can be calculated based on the nature of the information recorded and the quantity of information recorded. This can end up being many times larger than the storage requirements of the program itself!

14. Characteristics of Storage There are a number of different types of storage. You will be required to differentiate between the types and select suitable types to use based on a number of characteristics Capacity: The capacity of a storage device is how much information it can store. The capacity of storage devices is not limited in the same way as memory is as storage is broken up into blocks that are much larger than the locations used in memory Capacity is measured in the same units as computer memory: 1bit=A single 1 or 0 1 byte=8 bits 1 kilobyte (KB)=1024 bytes 1 megabyte (MB)=1024 kilobytes 1 gigabyte (GB)=1024 megabytes 1 terabyte(TB)=1024 gigabytes Storage capacities are currently typically measured in gigabytes and terabytes.

15. Rewritable / recordable / read only: This is whether or not the contents of a storage device can be changed. In general magnetic and solid state storage is rewritable – the contents can be changed again and again Some optical storage may be rewritable, but it is often recordable or read only instead. Recordable storage media can only be written to once. Read only storage media cannot be changed in any way. It is usually used to distribute information such as software, films and music.

16. Data Transfer Rate / Interface Type: The data transfer rate of a storage device is a measure of how quickly information can be transferred to and from it. Data Transfer Rate is typically measured in megabits (Mbit/s) and gigabits (Gbit/s) per second. This makes the transfer rate sound eight times faster than it actually is. It is important that the transfer rate remains proportional to the capacity of the storage device – A huge capacity is useless if it takes hours to access! The data transfer rate is related to the type of interface between the device and the computer: The data transfer rate cannot exceed the maximum speed allowed by the interface. However, it is perfectly possible for a storage device to have a lower data transfer rate then the interface it uses to communicate to the computer – For example, a hard disk drive’s transfer rate is often much slower than the notional maximum transfer rate of its SATA interface. SATA Interface Actual transfer speed based on rotation speed of disc and other physical limits: 1030 Mbit/s Interface speed: 16 Gbit/s Hard Disk The Computer

17. Built in / External: A built in or internal storage device is located physically inside the casing of a computer. Built in storage devices are only as portable as the computer they are part of, as the casing has to be opened to remove them. Interfaces such as SATA are used to connect the device to the rest of the computer External storage devices are located outside the casing of the computer. They can easily be unplugged and carried to another computer, making them very portable. USB is a common interface used by external storage devices. Internal HDD External HDD

18. Types of Storage Optical Storage: Optical storage works by encoding data physically on the surface of the media. Data is read by shining a laser onto the surface and detecting how it reflects back. DVDs and high definition, or blu-ray, DVDs are the most common optical storage media. CDs are still used in some places Transfer rates are measured in multiples of drive speed. Different optical media drives will operate at different multiples – for example 24x drive speed is common for DVDs Optical storage is cheap in terms of entire unit cost – an individual DVD can be pressed very cheaply. Optical MediaCapacity1x Drive Speed CD700 megabytes1.2 Mbit/s DVD4.7 gigabytes11 Mbit/s Blu-ray50 gigabytes36 Mbit/s

19. Magnetic Storage: Magnetic storage works by encoding data as a magnetic charge on a magnetisable surface. Data is read by detecting how magnetised a section of the surface is Hard disc drives are the most common type of magnetic storage. Magnetic tape still sees some use for the purpose of large backups Transfer rates on how fast the read head of the storage device can get to the location on the surface where the data is stored. On a hard disc, this depends on the rotation speed of the hard disc Magnetic storage is currently the cheapest form of storage in terms of cost per amount stored. Magnetic MediaCapacityTransfer Rate Hard Disk DriveMeasures in terabytes Measured in Gbit/s

20. Solid State Storage: Solid state storage devices have no moving parts. They work by storing data on persistent, non-volatile memory chips Memory cards, memory sticks and solid state drives are common solid state devices Transfer rates are not limited by the time taken to find data in the media and can start transferring data instantly. Since there are no moving parts, issues such as friction causing heat build up do not apply either. Consequently, solid state storage is both faster than magnetic storage and harder to damage than magnetic storage Solid State MediaCapacityTransfer Rate SD Memory cardMeasured in gigabytesMeasured in hundreds of Mbit/s USB memory stickMeasured in gigabytesLimited by USB interface, potentially Gbit/s Solid state driveMeasured in gigabytes and terabytes Measured in Gbit/s

21. Questions – Storage Answer questions in full sentences! 1. Describe two forms of magnetic storage. 2. What advantage does magnetic storage hold over solid state storage? 3. Describe three forms of solid state storage. 4. Explain why solid state storage is both faster and harder to damage than magnetic storage 5. Describe two forms of optical storage. 6. Optical storage costs more per amount stored than magnetic storage. Explain why it is still in use 7. Copy and complete the following table of interfaces: InterfaceMax Transfer RateDevice and Storage Types it is used with SD Interface USB 2.0 USB 3.0 SATA 3.0

22. 8. The school has recorded its most recent show as a 2 hour long video so the pupils who took part can take home copies to show their families. Choose a suitable storage type for this and explain your decision, giving at least two reasons 9. A pupil at the school is doing an art project at home and school using their computer. They need to be able to transfer their work between places. Choose a suitable storage type for this and explain your decision, giving at least two reasons 10. Your new mobile phone includes a 1 gigabyte SD card as its storage. How many pictures can you take at 24bit colour with its 5 megapixel camera before you fill the card. Assume that the photos are not compressed 11. You’ve just attached a 48x speed external DVD drive to your computer using USB 2.0. However, it isn’t transferring data as quickly as you expected. Explain why this is happening and calculate the difference between the expected transfer rate for 48x speed DVD and the actual transfer rate you are getting.

23. Storage Trends The way we use storage is constantly changing. You are required to understand the trends in storage use and discuss them. The decline of optical storage: In the past, optical storage has been used as a method of distributing information. CDs and DVDs have been used to sell music, films and software because of the low cost of making an individual optical disk The decline of optical storage corresponds to the increasing availability and download speed of internet connections. As connection speeds have increased, the time taken to download some music, or a film, or a game has reduced: The contents of a CD can be downloaded very quickly. The contents of a DVD can be downloaded reasonably quickly Online services like iTunes, Netflix and Steam allow computer users to download music, TV and movies and games directly to their computer, as well as save on physical space in their homes by not having shelves full of CD and DVD cases! The usage of optical media is likely to continue to decline as download speeds increase further, although the use of higher resolution film and TV may delay this as it will make files larger.

24. Magnetic vs Solid State: Magnetic storage is currently the cheapest type of storage in terms of cost per capacity. Because of this, magnetic storage remains the most commonly used storage in desktop and laptop computers. Solid state devices have advantages over magnetic storage – the lack of moving parts means they can access data faster and are harder to damage. This makes solid state storage common in portable computers like tablets and smart phones. The capacity of the largest solid state devices is rising to match that of hard discs. As solid state technology is developed, it is rapidly becoming cheaper. These trends are likely to continue, whilst the improvement in magnetic storage technology is likely to be slower as it is more developed already. As the cost of solid state storage approaches the cost of magnetic storage, more and more computers are likely to start using it

25. Storage Strategies Storage devices can be used in a number of different ways. Different methods have advantages and disadvantages Offline Storage: Offline storage is storage media that is physically disconnected from the computer when it is not in use. The computer has no direct control over when it is used. Offline storage is usually portable storage media like external drives and USB memory sticks. Because it can be removed from the location of the computer, it is ideal for transferring data and for backup. The information is more secure from remote attacks and malware because it is not connected to the computer. Distributed Storage: In distributed storage, the information stored is held in a number of different geographical locations. Data is sometimes replicated at different locations to protect against accidental data loss. Distributed storage is also ideal for data sharing and collaborative work: Because data can be accessed from anywhere in the distributed storage network, it is easy for multiple people in different locations to work on the same information. This storage is now offline

26. Backup Backup is when an additional copy of information is created. In the event of accidental damage or loss, the backup is used to restore the information with minimal data loss. Backup storage media is required to be:  Cheap – the amount of data stored as backup may end up exceeding the amount of data on the original copy  High capacity – the entire contents of an information system will be required to be backed up  Portable – Ideally backup should be removed from the location of the original data, as this reduces the likelihood of it being caught in the same incident that destroys original data The most commonly used media for backup in large organisation remains magnetic tape as it fulfils all three criteria

27. Backup Strategies A backup strategy describes how backup is made for an information system. Different backup strategies offer different advantages in terms of the storage capacity required, the ease with which backup can be made and the ease with which information can be restored from backup

28. Full Backup: A full backup is a complete copy of all the information stored on an information system Full backups are very simple to create and restore from. However, if you require multiple backups taken at different times, each additional backup increases the amount of storage required by the full amount of all the information stored on the system 1 full backup2 full backups 4 full backups

29. Differential Backup: A differential backup stores of all the changes made since the last full backup Differential backups are a little more difficult to create, but still relatively simple to restore – simply restore the full backup and then apply the differential back up needed. As time progresses from the original full backup, the size of the differential backup will increase. If you are storing multiple differential backups, some of them will included repeated information 1 full backup Differential backup 1 Differential backup 2 Differential backup 3

30. Incremental Backup: An incremental backup stores of all the changes made since the last full incremental backup Incremental backups are more difficult to create, and restore from – you need to apply the full back up and then several incremental backups to fully restore information. Incremental backups are more efficient in terms of capacity storage though – there will be no repeated data in your backups 1 full backup Incremental backup 1 Incremental backup 2 Incremental backup 3

31. Questions – Storage Trends, Strategies & backup Answer questions in full sentences! 1. Why are CDs less likely to be used for selling music than they were a few years ago? 2. Use the internet to find figures for the approximate cost per gigabyte of solid state drives and magnetic hard disc drives. Discuss how these figures have been changing 3. Explain what offline storage is 4. Give one reason why offline storage might be considered more secure, and one reason why it might be considered less secure. 5. Explain what distributed storage is 6. Explain why it is important to make backups. 7. Give one advantage and one disadvantage of using full backups 8. Give one advantage and one disadvantage of using differential backups 9. Give one advantage and one disadvantage of using incremental backups

32. Compression Compression reduces the size of a file by encoding it in a way that uses fewer bits. Compression is useful as it means more files can be fitted onto the same space in a storage device. Files will also download over the Internet faster as well The compression ratio is the extent to which a compressed file is smaller than its uncompressed original A number of standard file formats have inbuilt compression: GIFs, PNGs, JPEGs, MP3s and MP4s Compression Ratio = Uncompressed Size Compressed Size

33. Lossless Compression A compression method can be described as lossless if the information can be decompressed back to its original with no loss of data Lossless compression must be used when compressing text information and programs – data loss in these cases would be unacceptable and programs wouldn’t be able to run correctly The compression ratio of lossless compression tends to be lower than the compression ratio of lossy compression. GIF files and PNG files both make use of lossless compression

34. Run Length Encoding: Run length encoding is a very simple graphical compression method. In RLE compression, instead of repeating the same colour for several pixels, the file notes the colour and the number of times it appears. This reduces the amount of information stored. RLE is useful for simple images with few colours LZW Encoding: LZW recognises common patterns in a file. Instead of storing each pixel individually, it builds up a dictionary of common patterns of pixels and stores each occurrence of each pattern. This reduces the amount of information stored. LZW also works very well for encoding information stored as text. 1x 2x 5x Instead of…

35. Lossy Compression Lossy compression works by removing information or reducing the accuracy / level of detail to which information is stored. The original file cannot be recovered by decompressing a lossily compressed file Lossy compression is acceptable in situation where the human senses can’t perceive the difference between the compressed and uncompressed file. The compression ratio achieved by lossy compression tends to be much higher than that for lossless compression. Lossy compression is used for image, sound and video files such as JPEG, MP3 and MP4

36. JPEG: In JPEG encoding, the image is split into a number of small blocks. These blocks are simplified using a complicated mathematical formula. This effectively reduces the level of detail of each block, reducing the number of colours stored, and allowing the picture to be stored as patterns of pixels rather than individual pixels. This reduces the amount of information stored. In JPEGs, the extent of simplification can be varied as shown in the picture Highly compressed Lowly compressed

37. MP3 MPEG-2 Audio Layer III works by reducing the accuracy to which sound is stored. Sound is recorded by sampling the sound at frequent intervals. The sample rate is how frequently the sound is sampled every second. More frequently is more accurate. The sample depth is the accuracy of any given sample – the more bits used to store the sampled value the more accurate the sample is MP3 specifically chooses parts of the sound that are beyond the human ability to hear to compress. This means that the change in accuracy does not appear to affect the quality of the sound

38. MPEG-4: MPEG-4 is a wide ranging standard that includes several formats, including the MP4 video format MPEG compression works by reducing the information needed to store a video in two ways. Firstly it reduces the number of frames it needs to store. Where possible, it stores the difference between one frame and the next rather than the frame itself. This means a video is stored as a small number of key frames, with the gaps between them stored as changes made to the previous frames In addition to this, the frames themselves can be compressed in a manner similar to that used for JPEGs

39. Questions – Compression Answer questions in full sentences! 1. Explain how compression is of benefit in terms of: a)Data storage b)Networking 2. What is meant by lossy compression? 3. Explain why lossy compression is not suitable for text data 4. Why is lossy compression suitable for image and sound data? 5. Describe in detail how MP3 compression works 6. Explain in detail how MPEG compression works 7. What is meant by lossless compression? 8. Why isn’t lossless compression suitable for photographs? 9. GIFs use LZW compression. Explain in detail how LZW compression works 10. Calculate the compression ratios for the following compressed images a)A 30 megabyte bitmap image compressed to a 5 megabyte GIF b)A 10 megabyte bitmap image compressed to a 640 kilobyte JPEG

40. Operating Systems The operating system of a computer is a program that manages the hardware and software of that computer. Operating systems provide a layer of abstraction for other software applications and the user – variations in the computers hardware are effectively hidden from the user. Any software that is compatible with the operating system can be ran, provided the hardware meets the system specifications. This improves the portability of software – it doesn’t have to worry about things like how the processor addresses the memory as the operating system handles that.

41. Operating System Tasks The operating system of a computer is responsible for a number of tasks File Management: The OS is responsible for reading from and writing to the backing storage of the computer, as well as maintaining the structure of the file system. Memory Management: The OS allocates portions of the computers memory for programs and any data that they are using Input & Output Handling: The operating system handles communication between the computer system and the devices attached it. Device drivers are an operating system program for controlling specific items of hardware attached to a computer.

42. The User Interface: The OS is responsible for managing the user interface that the computer presents to the user Process Management: The kernel of the operating system is responsible for allocating the processors time to the various programs the computer is running. Error Handling: The operating system must deal with the problems caused by hardware and software failing to work correctly, making sure that the problems do not affect the rest of the computer

43. Operating Systems Trends – Mobile Operating Systems As smartphones have become more and more computer like, and as tablet computers have become more and more common, the operating systems used by these devices have become more and more important In some cases new operating systems such as iOS, Chrome OS and Android have been developed specifically for mobile devices. Other operating systems, such as Windows, have evolved to work with both traditional desktop and laptop computers as well as mobile devices. Making their operating system more portable like this helps reduce the costs for Windows’ developers Mobile OSes have to consider the different input and output methods used by mobile devices. In some cases this has lead to them working noticeably different from desktop OSes.

44. Software Purchase & Licensing A software license is a legal document that describes how an item of software may be used and distributed. A number of different models are used for selling software. With software increasingly sold by download rather than distributed via optical media, software developers have had greater freedom in coming up with methods for getting software to the user Single User License: The software is licensed to one user only. This may be to use one installation only, or may allow multiple installations provided only the licensed user uses the software Multiple User License: As the single user license, but more than one person can use the software Site License: In this case, the software is licensed to be used on a specific location. This form of licensing is particularly common for organisations such as schools and businesses.

45. In addition to the software license, there are a number of different ways in which software can be purchased or obtained. Commercial Software: The user has to pay to obtain the software, either with a one time purchase cost or using a subscription model Commercial software is usually proprietary – the developers have retained their rights under Copyright law. Such software is usually licensed only for use by the user and cannot be redistributed by them Free Software: The user does not have to pay to use free software. Usually free software can be redistributed by the user. Free software is sometimes also open source. Open source software is distributed with a license that allows the user to modify the program code and redistribute it Freemium Software: Freemium software models are free for a basic version of the software, but the user has to pay to unlock either a full version of the software, or additional features. Freemium software often makes use of micro transactions Firefox is an example of open source software

46. Portability Portability is a measure of how easily an item of software can be transferred from one computer environment to another. Different computer systems behave in different ways and have different capabilities, although operating systems can help mitigate some of these differences. To make software portable usually means either re-writing part of the code to take advantage of how a different system works. Alternately software can be designed to be portable initially, by making it behave in generalized ways. In this case it may end up not making best use of the hardware available to it. Making software portable is advantageous for developers  It ensures the software can reach the widest possible audience, meaning it can be sold to more people  It can reduce the cost of development as compared to making specialised software for several different computer systems

47. Questions – Operating Systems Answer questions in full sentences! 1. What is meant by an operating system? 2. Explain how an operating system aids the portability of software 3. Describe in detail four tasks that the operating system is responsible for 4. What advantages are there to the software developer in making software more portable. 5. Describe a disadvantage associated with making software more portable 6. Explain what is meant by proprietary software. 7. Explain what is meant by open source software