Digital Technology 2650 考試技巧

常見錯誤

1. 1high涉及分數: 6QWC extended evaluation

   In 6 mark QWC evaluation questions, a hotel booking changeover, bitmap versus JPEG, and similar scenarios, candidates give a correct general definition of each side but never connect it back to the scenario in the question.

   如何避免: State the general point in one sentence, then add a second sentence saying what it means for the specific scenario given. Do this for both sides of the argument, not just one.
2. 2medium涉及分數: 4Modulus 11 check digits

   Modulus 11 check digit calculations are attempted without showing the weighting order or the remainder, so a single arithmetic slip loses every mark in the calculation rather than just the accuracy mark.

   如何避免: Write each digit with its weight underneath, show the sum, then show the division by 11 and the remainder before stating the check digit. Method marks are available even if the final digit comes out wrong.
3. 3high涉及分數: 5Data flow diagrams

   Level 1 data flow diagrams connect an external entity straight to a data store, or leave data flow arrows unlabelled.

   如何避免: Route every flow through a process, never directly between two external entities or between an external entity and a store, and label every arrow with the data it carries.
4. 4medium涉及分數: 4Requirements analysis

   Functional and non-functional requirements get mixed up, candidates list a security or performance requirement when the question asks what the system must do.

   如何避免: Ask whether the point is a task the system carries out, which is functional, or a quality the system must have while it works, which is non-functional, before writing it down.
5. 5medium涉及分數: 3Backup strategies

   Differential and incremental backup get described as the same thing.

   如何避免: State it precisely. Differential backs up everything changed since the last full backup. Incremental backs up only what changed since the last backup of any type, full or incremental.
6. 6medium涉及分數: 2Two's complement representation

   Two's complement boundary values are given as plus 128 for the maximum positive value in an 8 bit signed byte.

   如何避免: The maximum positive 8 bit two's complement value is plus 127, binary 01111111, because one bit pattern is reserved for zero. Learn the boundary pair, minus 128 to plus 127, as a fact rather than deriving it under time pressure.
7. 7low涉及分數: 3Fetch execute cycle

   Fetch execute cycle answers describe fetching an instruction in general terms instead of naming the registers in the correct order.

   如何避免: Give the exact sequence. The address in the Program Counter copies to the MAR, the instruction at that address copies to the MDR, and the MDR content copies to the CIR. Naming registers out of order loses marks even when the general idea is right.