Computer Science · May / June 2017 · Paper 2 SL · Question 3

3. A phone company stores the SMS text messages that are sent between its own subscribers and only these subscribers. • Each subscriber that sends messages has an associated data structure where details of their SMS text messages are stored. • The sender’s phone number and name, followed by the details of each individual SMS text message are collected as they occur. • The details stored for each SMS text message are the receiver’s phone number, name and text message. For example, consider the following two data structures: 1111, fred, 1234, smith, Hi there, 1234, smith, Call me, … 1234, smith, 1111, fred, Later, … The first data structure is associated to a sender whose phone number is 1111, and has sent two SMS text messages to another subscriber whose phone number is 1234. The second data structure is associated to a sender whose phone number is 1234, and currently contains the details of just one message.

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