U2: Example Exam Questions Flashcards
How could an internet connection be provided to a system that could be used when cycling. (3)
Tether to a smartphone/mobile hotspot (1) using bluetooth/Wi-Fi/USB (1) to share the smartpohnes’s data connection (1)
OR
Use a 3G/4G connection (to access the internet) (1) to connect to a mobile phone network (1) this may require a subscription / SIM from the data provider (1)
Give 2 reasons why using Wi-Fi to connect to public hotspots may negatively affect the performance of the system. (2)
¬ Unreliable signal ( due to movement) / short range signal
¬ Dependent on Wi-Fi hotspot being available
¬ Constant searching for a signal will increase battery consumption
¬ Wi-Fi signal is prone to interference (which may cause the signal to drop out/corrupt data).
¬ A shared connection so available bandwidth will be limited.
¬ There may be lots of users so download speed eill be slow
¬ May need to keep stopping in order to log in (to public hotspots).
Describe how an internal component could be used by the system to determine location. (4)
GPS reciever (1) will use the signal from (at least three) satellites (1) calculates longitude and latitude co-ordinates, triangulates (1) based on strength of the signals (from the satellites (1)
OR
Use Wi-Fi reciever (1) to identify publicly recorded Wi-Fi hotspots (1) and measure signal strength (1) to determine proximity to hotspots (1)
OR
Use 3G/4G/phone network antenna (1) to identify cell towers / unique ID from cell towers (1) and measure signal strength (1) to determine proximity to towers (1)
The multifunctional system will make use of a central processing unit (CPU) designed for mobile devices. Explain two reasons why the features of a mobile CPU are more suitable for mobile devices. (4)
They are usually smaller than microcomputer/ server processors/small form factor (1) which will reduce the size and weight of the device.
OR
They have low power drain (1) which makes them suitable for battery-powered devices / will need charging less often (1)
OR
They produce less heat than microcomputer/server processors (1) so do not require heatsinks/ additional Cooling (1)
Describe how the CPU and GPU share work to improve computer performance. (4)
¬ GPU has a parallel structure / can process large amounts of data in parallel (1)
¬ GPU (more suited to) processes commands/instructions related to shapes/colours/rendering (1)
¬ CPU performs (other) instructions /calculations (1)
¬ GPU reduces the load on the CPU (1)
¬ Which will reduce delay/buffering/lag (1)
Describe how ‘lossy’ compression reduces the file size of video and audio files. (2)
¬ Uses an algorithm (1)
¬ Alters samling rate / bit rate / colour depth (1)
¬ Removes repeated/ unnecessary data (1)
Describe one way that using ‘lossy’ compression will have a negative effect on the use of the audio file. (3)
Metadata may have been removed (1) which will limit additional features available (1) such as track IS / Album art (1)
OR
May alter the file format (1) which may require specialist software/CODEC (1) limiting the devices it can be used on (1)
OR
Data will be (permanently) lost (1) during conversion (1) so future editing cannot be completed as accurately (1)
OR
Sound quality/accuracy will be reduced (1) by removing higher and lower frequencies / altering sample rate (1) which may affect the types of output device it is suitable for. (1)
Explain one benefit of using FTP to transfer the files to the NAS (3)
Compatible with / can be used alongside other protocols (1) such as SSH (1) to provide a secure connection / to improve security (1)
OR
Keeps an open connection (1) between the client and server (1) Which makes it suitable for extended session (1)
OR
Allow direct connection with the NAS (1) using NAS’ IP address (1) improving data transfer times (1)
OR
Allow connection from any location (1) using an IP address (1) so NAS can be accessed using ad hoc networks / internet (1).
What factors would need to be considered when implementing back-up procedures to NAS for multiple devices including laptops, Desktop PCs, tablets and smartphones. (6)
¬ Scheduling
Night time bakcups
Avoid geavy use times to maximise bandwidth
Leave devices on overnight
Sync data on devices to a folder on the server
Folder on server can be bakced up without the devices being turned on
¬ Type of back-up
differential
Incremental
to reduce data baing backed up at one time.
¬What to bakc-up
Complete backup everytime
But this could lead to duplicate data so the storage space would be large
¬ Connection type
Wi-Fi - may not provide sufficient bandwidth
Syncing portable devicdes in background - could reduce device performance
¬ Security
Security
Methods
Explain why the use of the queue data type is more appropriate than a stack for this system. (4)
¬ Queue is a FIFO structure (1)
¬ Stack is a FILO structure (1)
¬ Using a queue orders are processed as they are recieved (1)
¬ whereas the stack will process them in reverse order (1)
¬ (queue) processes the orders more fairly (1)
¬ (queue) avoids customers who order first waiting a long time (1)
One of Carter’s staff members is concerned about the security of the menu and ordering system. Discuss how the hardware and layout in Figure 2 may affect the security of the system and the impact this may have on Carter’s business. (8)
¬ Terminals are close so customers could see others card/pin numbers while at the checkout.
¬ PCs are exposed so people could restart/insert removable media that could bypass security or introduce viruses to the system
¬ Card readers are accessible so they could be interfered with to try to steal bank details.
¬ Ethernet / network sockets are exposed so unauthorised users may connect other devices to gain access to the network
IMPACTS
¬ Loss of revenue
¬ loss of customer confidence
¬ System down time
¬ Issue processing orders/ Accuracy of orders
¬ loss/theft of data
¬ Legal action resulting from not adequately protecting customer data
Analyse how the features of the two interfaces will affect the use and performance of the system. (8)
GRAPHICAL INTERFACE
¬ Improves accessibility as images aid understanding for users.
¬ Better use of screen space using icons/images for links so individual buttons can be smaller.
¬ Users may find It more engaging.
¬ Image data takes up more space than textual data.
¬ High numbers of/ high-resolution images may cause the system/screens to load more slowly than other types of interface.
¬ If high resolution images are used the system may need to be more powerful with larger storage space, faster processors, etc.
¬ If images don’t accurately show the food items, customers may complain.
MENU-BASED INTERFACE
¬ If there is a logical structure to the system, it is intuitive to use.
¬ Can integrate with accessibility systems easily (such as voice control) as limited options/ commands can be programmed for each screen.
¬ Reduces development time as they can often be generated by the programmer and do not require specialist graphic designers.
¬ Relatively easy to use, only a limited number of options are provided at one time.
¬ Can be frustrating to use if the item you want is several menu layers down.
When the study is being conducted a large amount of data is transmitted. Data transmitted to Shania’s laptop include:
• data collected by the sensors
• image and video data collected by the cameras
• sound data from the microphones.
Data transmitted by Shania’s laptop include:
• control signals from the laptop to the connected devices
• copies of the data collected by the sensors, which are sent to a server in her office to be backed up
• daily observations and chosen data, which are uploaded to a website for colleagues and other scientists to see.
Shania wants to make sure that all data is as accurate as possible. Errors caused by data being corrupted during transmission need to be corrected.
Discuss error correction systems that could be used and the implications for Shania. (10)
APPLICATIONS ¬Automatic repeat request (ARQ) - data sent contains error detection codes to determine if the recieved data is different of that that was sent. If the check determined that data is incorrect, it sends a resent request to the source computer , which sends the data again. ARQ protocols include: ¬ Stop-and-wait ARQ ¬ Go-Back-N ARQ ¬ Selective Repeat ARQ
¬Forward error correction (FEC) / Error correction Code (ECC) - uses data redundanct to help reduce errors by not requiring data to be resent. Sent data includes extra data that cane be used to correct errors when they are detected. FEC is usually used for data that is not stored and is non-repeatable (such as data sent to sensors).
IMPLICATIONS
ARQ requires a connection that allows 2-way communication so it would not be appropriate for data from the sensors as they would mosty likely be a simplex xommunication channel. Sensors are also unlikely to store data after transmission.
Suitable for sending back-up, as there is likely a large amount of data being sent, ARQ will allow more data packets being dedicated to data to be sent (reduced redundancy). This transmission is 2-way and a copy of data will be saved on the laptop so a resend request can be completed.
FEC requires extra data to be sent in each packet , which increases the size of data packetrs, and/or can result in more data packets being required, which can create extra overheads in terms of bandwidth required as a lot of data is being processed. However, as corrupt data does not have to be useful in this context for transmitting the sensor data to the laptop
Shania’s laptop uses an operating system that is specially designed for data collection and manipulation tasks.
Discuss the role of the kernel in controlling and managing system components and tasks in Shania’s computer system. (12) 4b
PROGRAM EXECUTION
OS aids the fetch-decode-execute cycle as it communicates between the active program and the CPU/Computer hardware. When a program wants to perform an operation/instruction, this is sent to the kernal which translates the program code in aooropriate system calls, whic hprovides the CPU and related hardware with the appropriate commands at the appropriate time to ensure instructions are carried out as the program intended. Ther kernal also ensures the correct commands and data are sent between runnimg programs.
INTERRUPTS
An interrupt is any signal (from hardware or software) that is deemed to require immediate attention by the system. The OS controls the translation of inputs from peripherals and calls from software to decide if an input is an interrupt or not. The OS then ensures the interrupt is processed by the CPU immediately rather than being queued, as other instructions would be.
The kernal ensures that data that is being queued and processed at the time is the interrupt is saved (usually in CPU registers) and that the correct interrupt handler is executed. When the interrupt is dealt with, the OS will ensure that the CPU and hardware revert back to the saved state and resume processing.
MEMORY MANAGEMENT
The OS monitors active processes to ensure that they have sufficient memory to be carried out. The OS actively manages the amount of RAM for each process. (When multiple programs are running, more RAM is dedicated to the one being used by the user because more memory is neede to update the visual changes on the screen, handle user inputs, etc. Background programs only need RAM for vital processing. The kernal also provides the instructions for the hardware (CPU/RAM) to keep track of what data is in which memory location at any one time.
MULTI-TASKING
The kernal is responsible for controlling the process of ‘time slicing’, which is on way that a computer createsthe illusion of multiple things happening at once. A single processor cannot execute more than one instruction at a time, so the kernel ‘slices’ instructions into smaller pieces and dadicates processor cycles to executing these instructions. The OS will calculate which instruction required a greater percentage of processing time while maintaining the appearence of multiple processes being run simultaneously.
In modern multi-core and mutli-processor systems, the OS kernel uses a similar process to divide the instructions between threads, cores and processors. This is combined with ‘time slicing’ when there is a large amounts of data and cores etc. are in use.
DISK ACCESS
Computer storage devices are typically only read/write one piece of data at a time. Ther kernal will ensure that program instructions that require data to be written or retrieved from the storage disk are queued and/or given priorityand then passed to the required disk location, hardware or program. Disk access works in conjunction with memory management to ensure data that is not saved to secondary storage is kept in RAM for as long as it needs to be.
The kernel will also control which programs, users, etc. can read/write to the disk and which data they can access. This helps ensure security of data and ensure data doesn’t become corrupt due to being written over or attempted access by an unauthorised program or user.
FILE SYSTEMS
The Kernel ensures that stored data is in the appropriate format and in a way that allows the system to identify and retrieve data.
The file system will most likely allow journaling, which improves data reliability by keeping logs of what changes are made when data is saved and in some cases saving data in multiple locations in case of corruotion.
As Shania’s system is a specialised OS, it is likely to be GNI/Linus or Unix based, which means the file systems used to save data on the cameras (if they have local storage) are likely to be different (cameras are likely FAT32/NTFS file systems)/ These two systems are not directly compatible but some OSs provide tools that will translate the system for the kernel to process.
As this is likely to be GNU/Linux or Unix- based, the files system is likely to be less fragmented as the nature of the kernel ensures data is grouped wherever possible , which reduced fragmentation and the need to run ‘defrag’ software.
DEVICE DRIVERS
The Os kernel contain device drivers that will be responsible for communicating with the system’s hardware. the device drivers work as a translator for the operating system and program software. The drivers take the standard programming code/instructions provided by the system’s software and tun it into exact instructions that a device understands. This allows for programs to be used with a range of devices and does not require programmers to write programs for every possible combination of hardware and software.
