Explain why the Vernam cipher is a better choice.
Vernam cipher if implemented correctly is unbreakable / harder to crack
statistical analysis of ciphertext reveals nothing about plaintext;
More possible keys;
What is Caesar cipher a wrong choice
Caesar cipher can be easily cracked;
Explain the key difference between lossless and lossy compression methods.
lossless data compression can be reversed / The original data cannot be recovered if lossy compression has been used
Explain why dictionary-based compression is not very effective for compressing small amounts of text for transmission.
For small pieces of text there is little repetition (and so the compressed text will be similar in size to the original);
Describe how MIDI is used to represent digital music.
Music represented as sequence of MIDI duration , pitch or volume
MIDI messages are usually two or three bytes long
Bit rate is 31,250 bits per second;
State two advantages of using MIDI instead of sampled sound.
More compact representation;
No data lost about musical notes
The MIDI file can be directly output to control an instrument / a device;
Give two reasons why cockpit voice recorders store data using solid-state memory instead of using a traditional hard disk drive.
No corruption of data due to magnetic fields;
Faster write speed so more data could be recorded;
What is a pixel?
A picture element/the smallest illuminable element of a display/smallest addressable part of an image;
What does a resolution of 1024 × 1024 mean?
Display is made up of 1024 pixels wide/ and 1024 pixels high
How many colours can this computer system display?
256;
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.
Bitmap images store the colour of each pixel
images can contain lots of pixels;
It takes only a small amount of memory to store the properties of an object;
(Large) images can be composed of relatively few objects
What is meant by the resolution of a bitmapped graphic image?
number of pixels per cm
What is meant by the colour depth of a bitmapped graphic image?
The number of bits used to represent (the colour / greyscale value);
An image has 10 x 10 pixels. It is stored in an image format that is limited to 16 colours.
Calculate the image size in bytes.
1010;4÷8
Instead of using bitmapped graphics, images may be represented in a computer’s main memory using vector graphics.
State one advantage bit map compared to vector graphics
Does not deteriorate , bested used for photogrraphs
Give one advantage of vector graphics over bit-mapped graphics.
Can take up much less (memory) space
Image is more accurate; smooth edges
What is an even parity and an odd parity bit
in even the total number of 1s in
the transmitted data even.
in odd the total number of 1s in
the transmitted data odd.
. If the value of the received parity bit
conforms to the type of parity (odd or even) in use, then the received data is treated as
correct. Otherwise, the computer will request that the sender re-transmits the data.
What is majority voting , advanage and disadvantage
each bit of the data is transmitted multiple times. When the
data is received, the most commonly occurring value is taken to be correct.
+ majority voting doesn’t just detect the error but also corrects the error, meaning no need for retransmission
- volume of data being transmitted is
increased with the repetition of bits.
What is an ascii code and a uni code and what is the difference
ASCII makes use of 7 bits to represent 128 2^7 different characters
including A to Z, a to z, 0 to 9 and various symbols.
Unicode was introduced in 1991 to allow the representation of a wide variety of alphabets
by computers. The standard uses anywhere from 8 to 48 bits (1 to 6 bytes) per character,
allowing it to represent a much wider range of different characters than ASCII.
What is a parity bit checker advnatgae and disadvantage
A parity bit is a single bit added to a transmission that can be used to check for errors in the transmitted data.
+ Can detect error only if an odd
number of bits are changed.
- Whether using odd or even parity, if an even number of bits are changed during transmission, the error is not detected.
What is check sum advantage and disadvantage
An algorithm is used to determine the value of a checksum based on the data being transmitted. A simple algorithm that could be applied is the modulo function,Once received, the recipient can remove the checksum and apply the same algorithm as
was used when sending the data to ensure that the checksum matches the transmitted
data. If the two do not match, the recipient cannot correct the error itself so must request
that the sender re-transmits the data.
What is check digit , advanatge and disadvanatge
nly a single digit is added to the transmitted
data. This reduces the number of different algorithms
disadvantage of midi
cannot be used for storing speeech
What is RLE
nly a single digit is added to the transmitted
data. This reduces the number of different algorithm
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Database24
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SQL33
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Big data23
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Turing Machine9
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BNF12
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Internal Hardware Components73
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Data Structures50
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Network Communication111
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Functional programming12
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Theory of computation19
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Fundamentals of algorithims18
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Procedural Programming34
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Programming Paradigm16
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Boolean gate and logic20
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Data Representation25
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Number System33
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Regular Language10
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Software2
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Logic Circuit5
