Educerie · IB Diploma · Computer Science

Theme A — Topic test

Paper 1 Section A style · 20 marks · 30 minutes

Answer all questions. Use correct technical terminology throughout.

1. (a) Convert the denary number 173 into 8-bit binary. [2]

(b) Convert your answer to part (a) into hexadecimal. [1]

(c) Explain what happens when the value 255 is incremented by 1 in an 8-bit unsigned register. [2]

2. (a) State the function of the memory address register (MAR) and the memory data register (MDR). [2]

(b) Describe the fetch–decode–execute cycle. [3]

3. (a) Distinguish between the TCP and UDP protocols. [3]

(b) Explain how a message split into packets can be correctly reconstructed even when the packets arrive out of order. [2]

4. (a) Distinguish between a primary key and a foreign key in a relational database. [2]

(b) Define the term supervised learning. [1]

(c) A model scores 99 % accuracy on its training data and 62 % on its test data. Explain what this indicates. [2]

Total: 20 marks

Command terms in this test. Questions 3(a) and 4(a) say distinguish, which must be written as a comparison, not as two separate accounts. Question 2(b) says describe, so the steps in order are required but not the reasons. Questions 1(c), 3(b) and 4(c) say explain, so a mechanism or reason is needed.

Educerie · original questions written against the published IB syllabus structure for Computer Science Theme A, first assessment 2027. Last reviewed 5 September 2026.