U2T1 - Data Representation Flashcards
What is our number system? (2 names)
Denary number system (base 10)
What number system do computers use?
What is it also known as?
Binary
The base 2 number system
From right to left, how do the columns to show binary go?
1, 2, 4, 8, 16, 32, 64, 128.
What is the highest number you can make in binary with 8 digits?
255
Convert denary to binary…
42
146
00101010
10010010
Convert binary to denary…
01101011
11100110
107
230
What are 2 ways to show negative numbers in binary?
Ones complement + twos complement
Describe ones complement…
Convert 1’s to 0’s and 0’s to 1’s.
Find ones complement of…
01100011 (99)
10011100 (-99)
Describe twos complement…
Convert to binary, invert 1’s and 0’s, add one.
Using twos complement:
Convert -5 to binary.
0101
1010
1011 (-5)
Convert 1111 to decimal using twos complement.
1111
0000
0001
= -1
How might you find the highest number a set of bits could create?
2n - 1
What is the bit position on the right hand side called?
What about the left?
Least significant bit (LSB)
Most significant bit (MSB)
How might a bit be represented in a computer’s main memory?
Transistor switched on/off, capacitor charged/discharged etc.
How is data transmitted over telephone/radio?
What about magnetic disks (floppy/hard)?
Audio CDs, CD-ROMs & DVDs?
High + low pitched tones for 1s & 0s.
Magnetic field on coated surface (North-South/South-North)
Optically, surface does/doesn’t reflect light.
What is a bit?
A binary digit. (0 or 1)
How many bits in a byte?
8
How many bytes in a KB?
1024
How many KB in a MB?
MB in a GB?
GB in a TB?
1024
How many bytes in a megabyte?
1,048,576
Typical size + price for: Hard Drive DVD Flash Drive External Hard Drive
1 - 5 TB, £40 - £150.
4.7GB, £10.
8 - 32 GB, £8 - £11.
1 TB, £50.
What is a character?
A letter/digit/special character represent with bits and bytes.
What does a character set contain? Examples?
Letters, digits, punctuation marks, ‘control characters’ which are non-printing & used for special purposes. E.g. ASCII & Unicode.
What is ASCII?
American Standard Code for Information Interchange.
7 bit code representing 128 characters. Bits represents symbols + characters in ASCII. 8th bit is a parity digit for error checking. 96 displayable characters, 32 control codes, 8 bits would give a range of 255.
What is Unicode?
A worldwide character standard which allows for interchange, processing & display of written texts of majority of languages of the modern world. 16 bit, 65536 characters.
Why is data stored in binary?
It’s either on or off
What is a nibble?
4 bits, half a byte.
What is a crumb?
2 bits
