Data Representation

• Name the smallest measure of data

  A bit (or binary digit)
• how many nibbles are there in a byte

  2- there are 8 bits in a byte and 4 bits in a nibble so, $8\div4=$$2$
• how many terabytes are in 1 petabyte


  1000 (or 1024)
• which digits are used in the binary number system 


  1 and 0
• why do we need to convert data into binary


  computer can only process binary data. 0 represents 'off' and 1 represents 'on'
• True or False: 4-bit numbers can represent the denary numbers 0-255 


  False- 4-bit numbers can only represent the denary numbers 0-15
• what is the least significant bit in the binary number 1010


  0 (the right-most bit)
• what is the result of adding 1 and 1 in binary


  10
• when performing a 1 place left shift, is a binary number doubled or halved


  Doubled
• if a binary number is shifted 4 places to the right, what is the effect on the size of the number

  the number has been halved four times (divided by $2^2$ = 16 in denary)
• which letters are used as hexadecimal digits

  A,B,C,D,E,F.
• True or False: Computers can process hexadecimal data 


  False- computers can only process binary data
• what is the denary number 12 in hexadecimal

  C
• moving from right to left, how do the place values increase in hexadecimal


  they go up in powers of 16
• how many bits can represent the same number of values as two hexadecimal digits


  8
• what is a character set 


  a character set is a collection of characters that a computer recognises from their binary representation
• which character set is larger, Unicode or ASCII 


  Unicode
• what is the size of a text file (in bits) that uses 8 bits per character and contains 80 characters


  $8\times80=$$640$ bits
• what is colour depth 


  the number of bits used for each pixel
• Calculate how many different colours a 5-bit image can use


  $2^5$$=$$32$
• what is the formula that relates file size, image resolution and colour depth


  File size (bits) = image resolution x colour depth

  or

  width (pixels) x height (pixels) x colour depth
• what is meant by the term sample rate 


  the sample rate is the number of audio samples taken per second
• what is the formula that relates file size, sample rate, bit depth and duration

  File size (in bits) = sample rate (In Hz) x bit depth x duration (In seconds)
• what does compressing a file mean 


  reducing the size of the file (while trying to stay as true to original as possible)
• True or False: Lossless compression temporarily removes data


  True- it restores the data when the file is decompressed