Look inside the AQA GCSE Computer Science guide (8525)

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Look inside the AQA GCSE Computer Science guide

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AQA · GCSE · 8525
Computer Science
Active Recall Guide
664 questions
Computer ScienceContents
Contents
8 topics, 43 subtopics
  1. Algorithms75
  2. Programming124
  3. Data Representation143
  4. Computer Systems95
  5. Computer Networks76
  6. Cyber Security55
  7. Relational Databases and Sql48
  8. Ethical, Legal and Environmental Impacts of Digital Technology48
ii
ProgrammingQuestions
Programming
Data types
  1. What is a data type?
  2. What is the integer data type?
  3. What is the real data type?
  4. What is the Boolean data type?
  5. What is the character data type?
  6. What is the string data type?
  7. Which data type suits a phone number, and why?
  8. Which data type suits the price of an item in a shop?
  9. Which data type suits a record of whether a user is logged in?
12
ProgrammingAnswers
Answers
Data types
  1. A data type sets the kind of value a variable can hold. The data type also decides which operations can be carried out on that value.
  2. An integer is a whole number with no fractional part. Integers can be positive, negative or zero, such as 42, 0 and −7.
  3. A real is a number that can have a fractional part, such as 3.75 or −0.5. Some languages call a real a float.
  4. A Boolean holds only one of two values, True or False. Booleans are used in conditions and to record whether something has happened.
  5. A character is a single letter, digit, symbol or space. Examples of characters are 'A', '7' and '#'.
  6. A string is a sequence of characters, such as a name or a sentence. A string can also be empty, holding no characters at all.
  7. A string suits a phone number. Phone numbers can begin with 0 and are never used in calculations.
  8. A real suits a price, because prices such as 4.99 have a fractional part.
  9. A Boolean suits whether a user is logged in. The value can only be True or False.
13
Computer SystemsQuestions
Computer Systems
Logic gates, truth tables and Boolean expressions
  1. What does a NOT gate do?
  2. When does an AND gate output 1?
  3. When does an OR gate output 1?
  4. When does an XOR gate output 1?
  5. How does an XOR gate differ from an OR gate?
  6. Which symbols represent AND, OR, XOR and NOT in a Boolean expression?
  7. How are the logic circuit symbols for AND, OR, XOR and NOT told apart?
  8. Write (A OR B) AND (NOT C) as a Boolean expression.
  9. What is the output of A · B + C̅ when A = 0, B = 1 and C = 0?
34
Computer SystemsAnswers
Answers
Logic gates, truth tables and Boolean expressions
  1. A NOT gate outputs the opposite of its single input. An input of 1 gives an output of 0, and an input of 0 gives 1.
  2. An AND gate outputs 1 only when both of its inputs are 1. Any other combination of inputs gives 0.
  3. An OR gate outputs 1 when at least one of its inputs is 1. The output is 0 only when both inputs are 0.
  4. An XOR gate outputs 1 when exactly one of its inputs is 1. The output is 0 when both inputs are the same.
  5. An OR gate outputs 1 when both inputs are 1. An XOR gate outputs 0 when both inputs are 1, because its inputs must differ.
  6. A dot (written . or ·) represents AND and a plus sign represents OR. The symbol ⊕ represents XOR, and a bar over a term represents NOT.
  7. An AND gate has a flat back and a rounded front, like a letter D. An OR gate has a curved back and a pointed front, and XOR adds a second curved line behind it. A NOT gate is a triangle with a small circle at its tip.
  8. The expression is (A + B) · C̅. The brackets make sure A OR B is worked out before the AND.
  9. The output is 1. A · B gives 0, but C̅ gives 1, and 0 OR 1 is 1.
35
Relational Databases and SqlQuestions
Relational Databases and Sql
Relational databases and keys
  1. What is a database?
  2. What is a relational database?
  3. What is a table in a database?
  4. What is a record in a database table?
  5. What is a field in a database table?
  6. What is a data type in a database?
  7. Why is each field in a database given a data type?
  8. What is a primary key?
  9. Why would a surname be a poor choice of primary key for a Student table?
56
Relational Databases and SqlAnswers
Answers
Relational databases and keys
  1. A database is an organised, persistent collection of data. The data is stored so that it can be searched, sorted and updated easily.
  2. A relational database stores data in several separate tables that are linked together. The links are made through fields the tables share.
  3. A table holds the data about one kind of thing, such as students or books. A table is made up of rows and columns.
  4. A record is one row of a table. A record holds all the data about a single item, such as one student.
  5. A field is one column of a table. A field holds one piece of data about every record, such as each student's surname.
  6. A data type sets what kind of value a field can hold. Common data types are integer, real, text, Boolean and date/time.
  7. A data type stops the wrong kind of value being entered, such as letters in a price field. The type also lets values be sorted and calculated correctly.
  8. A primary key is a field that uniquely identifies each record in a table. Two records in the same table can never share a primary key value.
  9. Two students can share the same surname, so a surname does not identify one record. A unique StudentID is used instead.
57
Keep going
664
questions
43 subtopics

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664 questions
Across 43 subtopics, every one of them from specification 8525.
One PDF
Print it, or work from a screen with a notebook beside you.
Answers after, not beside
Covering the answers is a matter of not turning the page, which is what makes the closed-book pass possible.

How the guide is worked

Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.

  1. Step 1 · Closed book

    Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.

  2. Step 2 · Open book

    Go back to the top. Read each printed answer and write it out in full, including the ones you had right.

  3. Step 3 · Closed book again

    Same questions, same order, from memory. The gap between pass one and pass three is the session result.

Read the full method, the return schedule and the research behind it.

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