a) Three digital sensors, A, B and C, are used to monitor a process. The outputs from the sensors are used as the inputs to a logic circuit. A signal, X, is output from the logic circuit:
Output, X, has a value of 1 if either of the following two conditions occur:
– Sensor A outputs the value 1 OR sensor B outputs the value 0.
– Sensor B outputs the value 1 AND sensor C outputs the value 0.
Draw a logic circuit to represent these conditions.
b) Copy and complete the truth table for the logic circuit described in part a).
c) Write a logic statement that describes the following logic circuit.
a) Write these six stages of the Von Neumann fetch-execute cycle in the correct order.
– Instruction is copied from the MDR and is placed in the CIR
– The instruction is executed
– The instruction is decoded
– The address contained in PC is copied to the MAR
– The value in PC is incremented by 1
– Instruction is copied from memory location in MAR and placed in MDR
b) Explain how the following affect the performance of a computer system.
i) Width of the data bus and address bus.
ii) The clock speed.
iii) Use of dual core or quad core processors.
c) A student accessed the BIOS on their computer. They increased the clock speed from 2.5 GHz to 3.2 GHz.
Explain the potential dangers in doing this.
a) A company is developing a new games console. The game will be stored on a ROM chip once the program to run the new game has been fully tested and developed.
i) Give two advantages of putting the game’s program on a ROM chip.
ii) Explain why the manufacturers would use an EPROM chip during development.
iii) The manufacturers are also using RAM chips on the internal circuit board.
Explain why they are doing this.
iv) The games console will have four USB ports.
Apart from the need to attach games controllers, give reasons why USB ports are incorporated.
b) During development of the games console the plastic parts are being made by a 3D printer.
Give two reasons why the manufacturer would use 3D printers.
A buffer is 2 MiB in size. The lower limit of the buffer is set at 200 KiB and the higher limit is set at 1.8 MiB.
Data is being streamed at 1.5 Mbps and the media player is taking data at the rate 600 kbps.
You may assume a megabit is 1 048 576 bits and a kilobit is 1024 bits.
a) Explain why the buffer is needed.
b) i) Calculate the amount of data stored in the buffer after 2 seconds of streaming and playback.
You may assume that the buffer already contains 200 KiB of data.
ii) By using different time values (such as 4 secs, 6 secs, 8 secs, and so on) determine how long it will take before the buffer reaches its higher limit (1.8 MiB).
c) Describe how the problem calculated in part b) ii) can be overcome so that a 30-minute video can be watched without frequent pausing of playback.
The editor of a movie is finalising the music score. They will send the final version of the score to the movie producer by email attachment.
a) Describe how sampling is used to record the music sound clips.
b) The music sound clips need to undergo some form of data compression before the music editor can send them via email. Identify the type of compression, lossy or lossless, they should use.
Give a justification for your answer.
c) One method of data compression is known as run length encoding (RLE).
i) Explain what is meant by RLE.
ii) Show how RLE would be used to produce a compressed file for the image below.
Write down the data you would expect to see in the RLE compressed format (you may assume that the grey squares have a code value of 85 and the white squares have a code value of 255).
A software developer is using a microphone and a sound editing app to collect and edit sounds for his new game.
When collecting sounds, the software developer can decide on the sampling resolution he wishes to use.
a) i) State what is meant by sampling resolution.
ii) Describe how sampling resolution will affect how accurate the stored digitised sound will be.
b) The software developer will include images in his new game.
i) Explain the term image resolution.
ii) The software developer is using 16-colour bit-map images.
State the number of bits required to encode data for one pixel of his image.
iii) One of the images is 16 384 pixels wide and 512 pixels high. The developer decides to save it as a 256-colour bit-map image.
Calculate the size of the image file in gibibytes.
iv) The bit-map image will contain a header.
State two items you would expect to see in the header.
v) Give three features you would expect to see in the sound editing app.
a) The following bytes represent binary integers using the two’s complement form. State the equivalent denary values.
i) 0 1 0 0 1 1 1 1
ii) 1 0 0 1 1 0 1 0
iii) Write the integer −53 in two’s complement form.
iv) Write the maximum possible range of numbers using the two’s complement form of an 8-bit binary number.
Give your answers in denary.
b) i) Write the denary integer 798 in binary-coded decimal (BCD) format.
ii) Write the denary number that is represented by the following BCD number.
c) Give one use of binary-coded decimal system.
When the guarantee on a computer runs out, the owner can take out insurance to cover breakdown and repairs.
The price of the insurance is calculated from:
– The model of the computer
− The age of the computer
− The current insurance rates
Following an enquiry to the insurance company, the customer receives a quotation letter with the price of the insurance. A program is to be produced.
The structure chart below shows the modular design for this process.
a) Copy the chart above and, using the letters A to D, add the labelling to the chart boxes.
b) Using the letters E to J, complete the labelling on the chart.
Some of these letters will be used more than once.
A queue Abstract Data Type (ADT) has these associated operations:
– Create queue
– Add item to queue
– Remove item from queue
The queue ADT is to be implemented as a linked list of nodes.
Each node consists of data and a pointer to the next node.
a) The following operations are carried out:
Copy the diagram below and add appropriate labels to show the final state of the queue.
Use the space on the left as a workspace.
Show your final answer in the node shapes on the right:
b) Using pseudocode, a record type, Node, is declared as follows:
Reserves space for 10 nodes in array Queue.
i) The CreateQueue operation links all nodes and initialises the three
Pointers that need to be used: HeadPointer, TailPointer and FreePointer.
Copy and complete the diagram to show the value of all pointers after CreateQueue has been executed.
ii) The algorithm for adding a name to the queue is written, using pseudocode, as a procedure with the header:
Copy and complete the pseudocode for the procedure RemoveName.
Use the variables listed in the identifier table.
A driver buys a new car.
The value of the car reduces each year by a percentage of its current value.
The percentage reduction is:
– In the first year, 40%
– In each following year, 20%
The driver writes a program to predict the value of the car in future years.
The program requirements are:
– Enter the cost of the new car (to nearest $)
– Calculate and output the value of the car at the end of each year
– The program will end when either the car is nine years old, or when the value is less than $1000.
a) Study the incomplete pseudocode which follows in part b) and copy and complete this identifier table.
b) Copy and complete the pseudocode for this design.