A bitmap image is 1000 pixels wide by 800 pixels high. The image takes up 400 kB of storage space when represented as a bitmap, excluding metadata. Calculate the maximum number of different colours that could appear in the image. You should show your working. correct answers • multiplying 400 by...
A bitmap image is 1000 pixels wide by 800 pixels high. The image takes up 400 kB of
storage space when represented as a bitmap, excluding metadata. Calculate the
maximum number of different colours that could appear in the image. You should show
your working. correct answers • multiplying 400 by 1000 // 400 000 shown in working;
• dividing 3 200 000 or 400 000 or 8000 or 3200 or 400 or 8 by a number;
• multiplying 1000 by 800 // 800 000 shown in working;
• multiplying by 8 to convert from bytes to bits;
• colour depth calculated as 4; • showing 2x as the last stage of the working, where x is
the value calculated so far;
The same image can also be represented using vector graphics. The vector graphics
representation of the image takes up 2 kB of storage space. Explain why the amount of
storage space taken up by the vector graphics representation of the image is
significantly smaller than the space taken up by the bitmap representation. correct
answers - Bitmap images store the colour of each pixel // vector graphics do not need to
store the colour of each pixel;
- The image contains 800 000 pixels // images can contain lots of pixels;
-Vector graphics store information about / properties of the objects that an image is
composed of; (A). "shapes" for "object"
- It takes only a small amount of memory to store the properties of an object;
- (Large) images can be composed of relatively few objects // there will be fewer objects
than there would be pixels // a single object might be equivalent to many pixels;
One advantage of vector graphics compared to bitmap graphics is that fewer bytes are
used to represent an image. State two other advantages of vector graphics compared
with bitmap graphics. [2 marks] correct answers - Individual objects / components /
parts of the image can be manipulated / edited / duplicated / copied independently;
- The image / individual objects / components / parts of the image can be enlarged /
scaled without loss of quality / without becoming pixelated // vector graphics are
resolution independent;
- If an object / component is deleted, the software knows what is behind it // no "hole" is
left in the image;
2 Describe what thin-client computing is and explain two reasons why a thin-client
system might be chosen in preference to a thick-client system. correct answers -
Processing is carried out // applications/programs are executed on an application server
(A. server);
- Clients are cheaper to purchase // clients can have lower hardware specification;
- Less configuration of clients is necessary // easier to configure/add a new client //
easier to replace a client;
- Simpler installation/updating of software (as only done on server);
,- Impossible to install unauthorised software on workstations // more secure as fewer
settings can be changed;
- Workstations consume less electricity/power; Licensing can be cheaper (as licence per
active user not per client); - - Longer MTBF for workstations // workstations do not
fail/break as often // workstations need less maintenance;
A data communications system can transmit four different signals. Each different signal
represents two bits of data.
Describe the exact relationship between the bit rate and the baud rate for this system
correct answers Bit rate is double / twice baud rate // baud rate is half bit rate; A. "It" is
double A. 2:1
Describe the relationship between the bit rate of the system and the bandwidth of the
transmission medium that the data is transmitted through. correct answers They are
(directly) proportional // the greater the bandwidth, the higher the bit rate; A. as bit rate
increases so does bandwidth as BOD
The system uses serial transmission. Describe the difference between the operation of
serial and parallel transmission. [2 mark] correct answers - Serial sends one bit at a
time / after each other whereas parallel sends multiple bits simultaneously/at same time;
- Serial uses a single wire / cable / path / line whereas parallel uses several / multiple
wires / cables / paths / lines;
Explain why a laser printer with a built-in wireless network adapter is likely to be a
suitable choice of printer for a small office.[3 marks] correct answers Why laser is
suitable (Max 2):
- Low cost per printed page // toner is cheaper (per page) than ink; Prints many pages
per minute // high speed;
- Options to install a (greater) variety of paper trays // (greater) variety of paper handling
options;
- Toner will not dry out; A. toner does not expire as quickly as ink; High resolution
output;
Why having a wireless adapter is suitable (Max 2):
- Easy to share printer between many devices;
- Can connect / print directly from computers / laptops with WiFi // no need to install a
network / cabling / wireless router to facilitate wireless / network / remote printing;
- Printer can be managed remotely;
- WiFi should be fast enough for likely number of users / documents (as small office);
- WiFi should have sufficient range for devices to connect (as small office);
Describe the principles of operation of a laser printer[6 marks] correct answers • Bitmap
of image built in memory from page description.
• (Negative) charge applied to (photosensitive) drum.
• Laser beam directed at drum. R. laser directed at paper.
,• Mirror is used to direct laser beam. • Where laser strikes drum charge is neutralised /
reversed / cancelled / discharged.
• (Negative) charge applied to toner.
• Toner sticks to drum based on charge // where the laser struck.
• Paper passed over drum and toner transfers to it.
• Positively charged transfer roller assists transfer of toner from drum to paper. A.
charge applied to paper assists with transfer.
• Heater fuses toner onto paper.
• For colour printing four different colour toners // four drums are required.
Use binary addition in 8-bit two's complement to perform the subtraction: 18 - 72 You
must show both your working and your final answer in binary. correct answers 1 mark:
Both 18 and -72 represented correctly in two's complement:
• 18: 00010010 • -72: 10111000
1 mark: Correct answer in binary: 11001010
Figure 6 shows a floating point representation of a number: Figure 6 (Mantissa,
0.1101000 Exponent, 0110)
Calculate the decimal equivalent of the number. You should show your working. correct
answers Award 2 marks for correct answer: 52
If answer is incorrect then award 1 method mark for either:
• showing correct value of both mantissa and exponent in decimal (Mantissa = 0.8125 //
13/16 Exponent = 6)
• showing binary point shifted 6 places to right in binary number
• indicating that final answer has been calculated using answer = mantissa x 2exponent
and used either the correct mantissa, the correct exponent, or both in this calculation.
In this floating point system, the closest possible representation of the decimal number
104.7 is shown in Figure 7.
(01101001, Mantissa Exponent, 0111)
Figure 7 By converting this number back to decimal it can be seen that the actual value
stored is 105 1 0 . 3 Calculate the absolute error that has occurred when representing
104.7 in Figure 7 correct answers 0.3 // 105 - 104.7 // | 104.7 - 105 |; A. award BOD
mark if correct method has been shown ie 105 - 104.7
but candidate has then made an error performing the subtraction operation R. -0.3
unless the accept point above also applies
Calculate the relative error that has occurred when representing 104.7 in Figure 7.
Express your answer as a percentage to two decimal places. correct answers 0.29(%);
A. 0.0029 // 0.3 ÷ 104.7
, A. follow-through of incorrect answer to question part 10.3 A. award BOD mark if correct
method has been shown but candidate has then made an error performing the division
operation
Explain why the relative error is usually considered to be a more important measure of
error than the absolute error. [1 mark] correct answers The effect / impact of an error
depends on its size relative to the number that is / should be represented // a particular
(absolute) error is more significant the smaller the number that is / should be
represented // a particular (absolute) error is less significant the bigger the number that
is / should be represented;
Describe how MIDI is used to represent digital music [2 marks] correct answers Music
represented as sequence of MIDI (event) messages; A. music represented as sequence
of instructions
A. "events" for "event messages" R. music represented as sequence of notes Max 1
mark for an example of data that might be contained in a message:
• Channel;
• Note on / note off;
• Pitch / frequency / note number;
• Volume / loudness;
• Velocity;
• Key pressure / aftertouch;
• Duration / length;
• Timbre;
• Instrument;
• Pedal effects;
• Pitch bend;
• Note envelope; MIDI messages are usually two or three bytes long; First byte of each
MIDI message is a status byte (others are data bytes); Bit rate is 31,250 bits per
second; MSB value of 1 indicates status byte, 0 indicates data bytes; Status bytes are
divided into a command and a channel number (4 bits for each); Sixteen channels are
supported;
Describe the difference between application software and system software[2 marks]
correct answers Application Software: Performs user-oriented tasks // performs tasks
that a user would still want to perform if they did not have a computer; NE. examples of
tasks System
Software: Software used in the management of a computer system; A. software that is
used to run a computer
Layer(s) of software that abstract the user from how the computer works; A. software
that hides complexity of hardware from user A. software that provides a virtual machine
Utilities are a type of system software. Describe what utilities are and include an
example of a utility in your answer [ 2 marks] correct answers Description (1 mark):
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller HopeJewels. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $17.49. You're not tied to anything after your purchase.
