1.4.1 - Data Types

Question 1

Units of Bits

Answer 1

Bit
Byte
Kilobyte
Megabyte
Gigabyte
Terabyte

Question 2

Data Types

Answer 2

Integer: Whole number
Real/Float: Decimal number
Character: Single letter/number
String: Multiple characters
Boolean: True or False

Question 3

Standard Binary

Answer 3

128, 64, 32, 16, 8, 4, 2, 1

Question 4

Negative Binary: Sign and Magnitude

Answer 4

• Most significant bit represents the sign
• 1 is negative, 0 is positive
• Makes calculations basically impossible
• Severely limits the size of numbers as the last bit doesn’t show value

Question 5

Two’s Complement:

Answer 5

• Write the number in positive
• Flip each bit
• Add one

Question 6

Binary Addition

Answer 6

0 + 0 = 0
0 + 1 = 1
1 + 1 = 10
1 + 1 + 1 = 11

Question 7

Binary Subtraction

Answer 7

• Convert the second number into negative binary
• Add the numbers

Question 8

Hexadecimal

Answer 8

• Used because it’s easier for humans to read and remember than binary, but easier for computers to convert to than denary
• Digits 0-9 then A-F, for a total of 0-15

Question 9

Floating Point Binary

Answer 9

8, 4, 2, 1, 0.5, 0.25, 0.125, 0.0625
Mantissa: The number
Exponent: How much you have shifted the decimal point by

The way that this system works means that certain numbers are really hard to represent (such as 0.3), hence computers often needing separate processors to work with these long binary numbers

The same Two’s Complement system can be used for negative decimal binary numbers

Normalised floating point binary numbers have only one zero before the first one (ie. 0.1101)

To add or subtract decimal binary numbers, the exponents must be the same

Question 10

Bitwise Manipulation and Masks

Answer 10

Bitwise manipulation: Applying logical operators to binary
Mask: The binary data that is being used

Not: Flips the data point
And: Returns 1 if both are 1
Or: Returns 1 if at least one is a 1
Xor: Returns 1 if only one is a 1

Question 11

Character Sets

Answer 11

• How a computer represents characters as binary digits
• Includes numbers and special characters

ASCII: 127 characters in 7 bit binary
- Small, so can only really be used for standard English characters
- But a smaller bit length means that the information takes up less storage space
- Uppercase letters start at 65, and lower case starts at 97

Unicode: Uses up to 4 bytes per character
- So can represent thousands of different characters from all of the world’s languages that couldn’t fit into ASCII