Section 2- Data Representation

• What is the smallest measure of data?

  Bits
• What do computers use to represent the flow of electricity?

  Binary digits (0s and 1s)
• What does a 1 represent?

  The presence of electricity
• What does a 0 represent?

  There is no presence of electricity
• How many binary digits are in a bit?

  1
• How many bits are there in a nibble?

  4
• How many bits are in a byte?

  8
• How many bytes are in a Kilobyte?

  1000 bytes
• How many kilobytes are in a megabyte?

  1000 kilobytes
• How many megabytes are in a gigabyte?

  1000 megabytes
• How many gigabytes are in a terabyte?

  1000 gigabytes
• How many terabytes are in a petabyte?

  1000 terabytes
• What order does the binary table go in?

  128, 64, 32, 16, 8, 4, 2, 1
• What does 0 + 0 make?

  0
• What does 0 + 1 make?

  1
• What does 1 + 1 make?

  0 carry the 1
• What does 1 + 1 + 1 make?


  1 carry the 1
• What is an overflow error?

  When a number has too many bits- larger than 8 bits
• What does a binary shift to the left do?

  Multiply the number by 2 for every shift
• What does a binary shift to the right do?

  Divides the number by 2 for every shift
• What can left shifts cause?

  Overflow errors - loss of accuracy/data
• How many different digits does hexadecimal use?

  16
• What are the digits used in hexadecimal?

  0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F
• What can binary also represent?

  Characters
• What are character sets?

  Character sets are collections of characters that a computer recognises from their binary representations- letters, numbers, symbols
• What are the main types of character sets?

  ASCII, Extended ASCII, Unicode
• How many different characters can ASCII represent?

  128 characters- its a 7-bit binary code
• How many characters can Unicode represent?

  Over 143,000 characters.
• What is an advantage of Unicode?

  It covers all major languages
• What is the formula for calculating text file size?

  File size (in bits)= number of bits per character * number of characters
• What are images stored as?

  A series of pixles
• What are most images we use called?

  Bitmap images
• What is the colour of each represented as?

  Binary code
• How can you have a greater range of shades and colours?

  Increasing the number of bits for each pixel
• What is the colour depth?

  The number of bits used for each pixel
• What increases the file size of an image?

  Colour depth and resolution
• What is the calculation for the file size of an image?

  File size = image resolution * colour depth = width * height * colour depth
• How do you work out the total number of colours possible?

  total number of colours= 2^n (n= number of bits per pixel)
• What is the resolution of an image?

  The number of pixels in an image
• What is metadata?

  The information stored in an image file which helps the computer recreate the image on screen from the binary data in each pixel