Data types Flashcards
1
Q
What are the basic data types?
A
- Real
- Integer
- String
- Character
- Boolean
2
Q
What is casting?
A
- When you convert one data type to another
- E.G: string to integer
3
Q
Units of digital information
A
- Bit: represents either a 1 or a 0
- Nibble: 4 bits
- Byte: 8 bits
4
Q
What are signed binary numberes?
A
- Unsigned: used to represent positive binary numbers
- Signed: used to represent negative binary numbers
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
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
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
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
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
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
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
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
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
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
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
16
Q
How to add and subtract floating point binary
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?
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?
A
- Left shift: doubles the number
- Right shift: halves the number
19
Q
What is bitwise manipulation and masks?
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?
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?
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
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?
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
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
