OCR Computer Science for A Level
Teaching and Learning Resources
Chapter 1: Computational thinking
ANSWERS TO QUESTIONS IN THE STUDENT’S BOOK
Page 15
Question
Think of some other techniques from computer science that translate into real-world problem
solving.
Answer




Looking up a name in a directory – linear search/binary search.
Standing in a queue waiting to be served – data structures.
Packing your bags for a trip – prefetching, caching.
Planning a route – shortest-path algorithm.
 Cooking a gourmet meal – parallel processing.
 Cleaning out your garage – keep only what you need.
 Storing books, box sets, etc. – hashing.
Page 17
Question
Consider the advantages of each level of detail given in this example. When would you use each?
Answer
Consider factors such as preferred method of travel, cost, time requirements, etc.
Question
A decimal number such as 21 can be decomposed into its separate digits; that is, 2 × 101 + 1 ×100.
1. Decompose the binary number 1000001.
Answer
26 + 20
Question
2. Decompose the decimal equivalent of binary 1000001.
Answer
6 × 101 + 5 × 100
Question
3. Decompose the hexadecimal decimal equivalent of binary 1000001.
Answer
4 × 161 + 1 × 160
OCR Computer Science for A Level Chapter 1
© Hodder & Stoughton Limited 2015
OCR Computer Science for A Level
Teaching and Learning Resources
Page 19
Question
What is the end condition in the binary search implementation given on this page?
Answer
if (high < low)
Page 20
Question
1. Define the term ‘recursion’.
Answer
Defining an object in terms of itself. It often refers to a function or procedure calling itself from
within the subprogram.
Question
2. GNU is an operating system. Explain why the name GNU is recursive.
Answer
The ‘G’ in ‘GNU’ refers to ‘GNU’ itself. It stands for GNU not Unix.
Question
3. A library accepts new members and stores data about them. It issues them with a card. It also
updates membership details when necessary. When the member leaves, the record for that
member is deleted.
Express this library system as a data-flow diagram.
OCR Computer Science for A Level Chapter 1
© Hodder & Stoughton Limited 2015
OCR Computer Science for A Level
Teaching and Learning Resources
Answer
OCR Computer Science for A Level Chapter 1
© Hodder & Stoughton Limited 2015