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AS & A Level Computer Science 9608 REVISION NOTES Question & Answers 2024
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AS & A Level Computer Science 9608REVISION NOTES Question & Answers
2024
1.1 Number Representation
What are binaries? - Correct Answers ✅o Values stored as a
series of ones and zeroes
o A single 0 or 1 is called a binary digit or bit.
o Any group of 0s & 1s can represent a character
128 64 32 16 8 4 2 1
00000000
o E.g. 65 in binary is 1000001
1.1 Number Representation
What are BCD Representation? - Correct Answers ✅o Each digit
in the number is written separately in a
series of 4 bits
o E.g. 398 in BCD
o 3 = 0011 9 = 1001 8 = 1000
o 398 = 0011 1001 1000
o Use of BCD: used in business applications (arithmetic)
where every digit has to be retained in a result
1.1 Number Representation
,AS & A Level Computer Science 9608
REVISION NOTES Question & Answers
2024
What are Hexadecimal Number? - Correct Answers ✅o The
base-16 number system (counting in 16)
o After 9, numbers represented by letters from A to F
256 16 1
000
-(HEXADECIMAL TO DENARY)
o E.g. A5 in Denary = (16×10) + (1×5) = 165
-(DENARY TO HEXADECIMAL)
o E.g. 65 in Hexadecimal = 65 ÷ 16 = 4 𝑅𝑒𝑚𝑎𝑖𝑛𝑑𝑒𝑟 1
∴ = 41 H
-(HEXADECIMAL TO BINARY)
o Quick way of translating hexadecimal to binary is by converting the
hexadecimal to BCD
o E.g.
A5 in Binary:
A = 1010, 5 = 0101
A5 = 10100101
,AS & A Level Computer Science 9608
REVISION NOTES Question & Answers
2024
1.1 Number Representation
What are 2's Complement? - Correct Answers ✅o We can
represent a negative number in binary by making the most significant
bit (MSB) a sign bit, which will tell us whether the number is positive or
negative
-128 64 32 16 8 4 2 1
MSB 0 0 0 0 0 0 LSB
1.1.2 Images
How data for a bit-mapped image is encoded? - Correct Answers
✅A bitmapped image is encoded by assigning a solid color to each
pixel.
1.1.2 Images
What are Pixels? - Correct Answers ✅Pixels are small blocks of
addressable areas and the color they have is represented by binary and
stored as bits.
1.1.2 Images
What are File Header? - Correct Answers ✅They are a few bytes
of binary and represents basic information about the graphic, such as
image resolution, size and number of colors.
, AS & A Level Computer Science 9608
REVISION NOTES Question & Answers
2024
1.1.2 Images
Define Image Resolution? - Correct Answers ✅It is the amount
of pixels an image contains per inch/cm
1.1.2 Images
Define Screen Resolution? - Correct Answers ✅It is the number
of pixels per row by the number of pixels per column.
1.1.2 Images
What is color depth? - Correct Answers ✅It is the number of bits
used to represent the color of a single pixel
An image with n bits has 2^n colors per pixel.
File Size = Number of Pixels x Color Depth
1.1.2 Images
What is a vector graphic? - Correct Answers ✅They are images
defined using mathematics &
geometry i.e. points, lines, curves & shapes/polygon(s)
Objects and properties are stored mathematically
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