Computer Science A-Level > Data types > Flashcards

Data types Flashcards

(24 cards)

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1
Q

What are the basic data types?

A
  • Real
  • Integer
  • String
  • Character
  • Boolean
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2
Q

What is casting?

A
  • When you convert one data type to another
  • E.G: string to integer
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3
Q

Units of digital information

A
  • Bit: represents either a 1 or a 0
  • Nibble: 4 bits
  • Byte: 8 bits
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4
Q

What are signed binary numberes?

A
  • Unsigned: used to represent positive binary numbers
  • Signed: used to represent negative binary numbers
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5
Q

What is the MSB?

A
  • Most significant bit
  • If MSB is 0, the number is positive
  • If MSB is 1, the number is negative
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6
Q

How is sign and magnitude used?

A
  • The first bit of the binary number is the MSB
  • The first bit tells you whether the number is positive or negative
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7
Q

Drawbacks of using sign and magnitude

A
  • The MSB purpose changes from representing a value to representing positive or negative
  • Losing the MSB halves the maximum possible size of the number that can be stored
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8
Q

How do you convert from denary to negative binary using two’s complement?

A
  • Start with the absolute value of the number (the positive value)
  • Invert all of the bits so the 0’s become 1’s and vice versa
  • Add 1
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9
Q

How do you convert from binary to denary using two’s complement?

A
  • Use the first bit as the negative starting point
  • The rest of the bits are used to count up from the starting point
  • E.G: 1010 - -8 is the starting point. You count up by 2. The denary number is -6
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10
Q

Why do we use hexadecimal?

A
  • A more human-friendly representation of binary-coded values
  • More concise as 4 bits is represented by 1 hex value
  • Less prone to error
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11
Q

What do you do if you have an overflow in binary addition / subtraction

A
  • Ignore the overflow
  • In two’s complement arithmetic, the overflow bit does not contribute to the actual value
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12
Q

What is the mantissa and the exponent?

A
  • Mantissa: the part of the number that holds the actual digits of the value
  • Exponent: controls how far the binary point moves, determining the scale of the number
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13
Q

What is fixed point binary?

A
  • The numbers after the decimal point represent the decimal place numbers: 0.5, 0.25, 0.125
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14
Q

How to represent a denary number as floating point binary?

A
  • Convert the number to fixed point binary
  • 6.75 = 0110.11 (MSB is 0)
  • Move the decimal place to the beginning: 0.11011
  • Decimal place moved 3 places so the exponent is 3
  • Mantissa: 011011
  • Exponent: 011
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15
Q

What is normalising floating point binary and how do you do it?

A
  • Ensures a consisten point of floating point binary representation
  • Shift the decimal palce to the left until it begins with 01 or 10
  • Adjust the exponent value by how much it was shifted
  • E.G: Mantissa is 0.0011, exponent is 0010
  • Shift decimal to the right to get 0.11
  • Adjust mantissa to 0000
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16
Q

How to add and subtract floating point binary

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A
  • Adjust the mantissa so both numbers have the same exponent
  • Add / subtract the mantissa as you normally would, exponent will stay the same
  • Normalise the number, adjust the exponent accordingally
  • Determine the sign value
17
Q

What are logical shifts?

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A
  • The process of moving the bits in a binary number to the left or to the right by a specific amount
18
Q

What does a left shift and right shift do?

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A
  • Left shift: doubles the number
  • Right shift: halves the number
19
Q

What is bitwise manipulation and masks?

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A
  • Bitwise manipulation uses logical operations such as AND, OR, XOR to manipulate binary numbers
  • Masks are applied to binary numbers to hide / manipulate their values
  • E.G: AND mask, the values will be changed if both the binary number and the mask number is a 1
20
Q

What is a character set and the 2 examples?

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A
  • A character set is a list of all of the characters and their associated binary code
  • They standardise the binary code for each character
  • 2 character sets: ASCII (American Standard Code for Information Interchange) and UNICODE
21
Q

What is ASCII?

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A
  • Uses 7 bits to encode each character, providing for 128 different characters
  • Extended ASCII uses 8 bits, allowing 256 different characters
22
Q

Limitations of ASCII

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A
  • Limited to 128 characters as it only uses 7 bits
  • Not suitable for multilingual text
  • No provision for modern symbols
23
Q

What is UNICODE?

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A
  • Created to be a solution to the limitations of ASCII
  • Uses a much larger bit range - up to 32 bits
24
Q

ASCII vs UNICODE

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A
  • ASCII is more storage-efficient, which characters requiring only 7 bits
  • UNICODE uses up to 32 bits, hence using more storage
  • UNICODE is able to represent many more characters than ASCII
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