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Grade 8 Computer Science — The shapes a network is built in

Work out how much cable a bus, star, ring or mesh needs, and what a single break costs each of them.

Name: ________________________

  1. 1.Five computers are joined in a mesh, so every computer has its own cable to every other computer. How many cables is that altogether?

  2. 2.One cable is cut in each of these networks. Sort each one by whether every machine can still reach every other machine afterwards.

    Groups: All of them can still reach each other · At least one is cut off

    • A mesh of four computers, every one joined to every other, with one cable cut
    • A star of six computers around a switch, with one outer cable cut
    • A bus whose one long cable is cut halfway along
    • A mesh of five computers, every one joined to every other, with one cable cut
    • A single ring of eight computers, with one link broken

  3. 3.In a star network each computer has one cable of its own to the switch in the middle. One of those outer cables is cut. What happens?

    • a) Every computer on the network is cut off from every other one
    • b) Nothing changes at all, because messages take a different route
    • c) The switch is cut off but the computers can still reach each other
    • d) The computer on the far end of that cable is cut off, and the rest carry on as before

  4. 4.Tap the one part of this star network that every message between two computers has to pass through.

    Write the number of the part.

    12345

  5. 5.A bus network joins nine computers along one long cable. The cable is cut, leaving four computers on one side of the break. How many pairs of computers, one taken from each side, have lost contact with each other?

  6. 6.Six computers are joined in a star. Each one has a single cable running to the switch in the middle, and no other cables at all. How many cables does the network use?

  7. 7.A star has eight computers around one switch. The switch itself stops working. How many of the eight can still reach another computer?

  8. 8.Twelve computers are joined in a single ring, each cabled to the computer on either side of it. How many cables does the ring use?

Answer key — Grade 8 Computer Science — The shapes a network is built in

  1. 1. 10
  2. 2. A mesh of four computers, every one joined to every other, with one cable cut → All of them can still reach each other; A star of six computers around a switch, with one outer cable cut → At least one is cut off; A single ring of eight computers, with one link broken → All of them can still reach each other; A bus whose one long cable is cut halfway along → At least one is cut off; A mesh of five computers, every one joined to every other, with one cable cut → All of them can still reach each other
  3. 3. d) The computer on the far end of that cable is cut off, and the rest carry on as before
  4. 4. 5 — The switch in the middle
  5. 5. 20
  6. 6. 6
  7. 7.
    • 0
    • none
  8. 8. 12