Packets and transmission methods — GCSE Computer Science practice questions

Question 1

A smart fridge sends a shopping list to a supermarket app. Before it is sent, the list is split into packets.

Which item is **not** stored in the header of a packet?

Accepted Answer

D: The part of the shopping list that the packet is carrying. The header holds the information needed to deliver and rebuild the data: the destination address, the originator's (sender's) address and the packet number. The part of the shopping list being carried is the actual data, so it is the payload, not part of the header.

Question 2

A wind farm sends readings from each turbine to a control building 800 m away. It uses serial transmission rather than parallel.

Which statement is a reason for choosing serial transmission?

Accepted Answer

A: The bits arrive in the order they were sent, so serial is reliable over long distances.. Serial sends one bit at a time down a single wire, so the bits arrive in the order they were sent and there is no skew. This makes serial reliable over long distances such as 800 m, and it is also cheaper because the cable needs fewer wires.

Question 3

A design club's laptop is connected by a 1 m cable to a 3D printer on the same bench. Large design files must reach the printer as quickly as possible. The printer sometimes sends messages back to the laptop, such as "Filament low", but never while a file is being sent to it.

Which transmission method is most suitable?

Accepted Answer

D: Parallel half-duplex. The cable is only 1 m long, so skew is not a problem and parallel transmission sends the large files fastest. The printer must be able to send messages back, but never at the same time as the laptop sends, so half-duplex is enough: parallel half-duplex.