Digital Technology 2650 考試技巧

常見錯誤

1. 1medium涉及分數: 3Networks: bandwidth and broadband

   Broadband is defined as simply fast internet rather than as wide bandwidth, and gets confused with bandwidth itself, the frequency range or data capacity of a channel.

   如何避免: Keep the two separate. Bandwidth is the capacity of a single channel. Broadband is a wide bandwidth transmission method that carries multiple channels or a high data rate at once.
2. 2medium涉及分數: 4Error detection (CRC)

   CRC error detection is described as just checking the data, without the mechanical steps, dividing by a fixed polynomial to generate a remainder, sending that remainder as a checksum, and recalculating it at the destination to compare.

   如何避免: Write the process as a sequence: the sender divides the data by a fixed number to get a remainder, sends that remainder alongside the data, and the receiver repeats the division and compares its remainder to the one received.
3. 3high涉及分數: 4Database normalisation

   Relational database normalisation, 1NF through 3NF, is completed without underlining primary keys or marking foreign keys at each stage.

   如何避免: Underline every primary key and clearly mark every foreign key in every intermediate table you draw, not just the final 3NF answer. The notation is assessed at each stage, not only the end result.
4. 4medium涉及分數: 3Computer Misuse Act

   Legislation questions give a general ethical opinion instead of naming the specific statutory offence, for example under Sections 1, 2 or 3 of the Computer Misuse Act.

   如何避免: Learn what each section actually covers: Section 1 is unauthorised access, Section 2 is unauthorised access with intent to commit a further offence, Section 3 is unauthorised modification. Name the section that matches the scenario.
5. 5medium涉及分數: 3SQL syntax

   SQL answers omit quotation marks around text literals, use INSERT INTO syntax inside an UPDATE statement, or leave out the WHERE clause on a DELETE command.

   如何避免: Quote every text literal, use UPDATE table SET field = value WHERE condition, and never write a DELETE statement without a WHERE clause unless the question specifically asks you to clear the whole table.
6. 6high涉及分數: 6QWC extended evaluation

   6 mark QWC questions discuss only the benefits of a technology, cloud storage or a star topology, for example, without analysing the drawbacks or vulnerabilities on the other side.

   如何避免: Plan both sides before writing. State the advantage, then the corresponding risk or limitation, for every point you raise, so the answer reads as an evaluation rather than a one-sided description.
7. 7low涉及分數: 2Error detection (parity)

   Parity bits are assumed to detect every transmission error, when in fact an even number of flipped bits leaves the parity unchanged and goes undetected.

   如何避免: State the limitation explicitly when asked to evaluate parity checking: it detects an odd number of bit errors but misses an even number, which is why stronger methods such as CRC are used alongside or instead of it.