The SQA publish previous Exam Papers. Working through the past paper question can be a useful way to revise, whilst getting a feel for the types of questions that you might find difficult.
In addition to the Past Paper the SQA also publish a Course Report. This document outlines the questions that candidates answered well, and those that candidates found challenging - along with why candidates found the question challenging. Using this can help direct your revision to the trickier concepts.
Below I've given direct links to all Past Papers, Marking Instructions & Course Reports (where available). For some questions I have recorded Walk-through videos, where demonstrate how to answer the question.
Any SQA Exam Papers pre-2019, do no align to the current Higher Computing Science Course Specification.
Below are modified version of the SQA Papers to only include relevant Questions. Note the Marking Instructions are for the full paper.
2018
2017
Mostly Software & Computer Systems
Marking Instructions
2016
Mostly Software