Look inside the Edexcel GCSE Computer Science guide (1CP2)

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Look inside the Edexcel GCSE Computer Science guide

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Edexcel · GCSE · 1CP2
Computer Science
Active Recall Guide
680 questions
Computer ScienceContents
Contents
6 topics, 41 subtopics
  1. Computational Thinking107
  2. Data128
  3. Computers95
  4. Networks92
  5. Issues and Impact88
  6. Problem Solving with Programming170
ii
DataQuestions
Data
Binary, states and unsigned integers
  1. Why do computers use binary to represent data and program instructions?
  2. Which kinds of data does a computer store as binary?
  3. What is a bit?
  4. How many different states can a binary pattern of n bits represent?
  5. How many different values can a 5-bit pattern represent?
  6. What is the smallest number of bits needed to give a unique code to each of 50 students?
  7. What is an unsigned integer?
  8. What range of values can an 8-bit unsigned integer hold?
  9. State the place values of the bits in an 8-bit unsigned binary number, from left to right.
12
DataAnswers
Answers
Binary, states and unsigned integers
  1. A computer's circuits are built from transistors that act as switches with two states, on and off. The binary digits 1 and 0 map directly onto those two states.
  2. A computer stores numbers, text, sound and images as binary. Program instructions are stored as binary patterns too.
  3. A bit is a single binary digit, either 0 or 1. A bit is the smallest unit of data a computer can store.
  4. A pattern of n bits can represent 2ⁿ different states. Each extra bit doubles the number of states.
  5. A 5-bit pattern can represent 32 different values. Five bits give 2⁵ = 32 combinations.
  6. Six bits are needed, since 2⁶ = 64 codes is enough for 50 students. Five bits give only 32 codes, which is too few.
  7. An unsigned integer is a whole number with no sign, so it can only be zero or positive. Every bit adds to the size of the number.
  8. An 8-bit unsigned integer holds values from 0 to 255. The largest value is 2⁸ − 1 = 255.
  9. The place values are 128, 64, 32, 16, 8, 4, 2 and 1.
13
ComputersQuestions
Computers
Secondary storage: magnetic, optical and solid state
  1. What is secondary storage?
  2. Why does a computer need secondary storage as well as RAM?
  3. How does secondary storage compare with main memory for speed and capacity?
  4. How does a magnetic hard disk drive store data?
  5. Why is a magnetic hard disk slower to access than a solid state drive?
  6. What are the advantages of magnetic hard disks?
  7. How does optical storage store and read data?
  8. Why can a Blu-ray disc hold more data than a DVD?
  9. What are the advantages and disadvantages of optical discs?
34
ComputersAnswers
Answers
Secondary storage: magnetic, optical and solid state
  1. Secondary storage is non-volatile storage that keeps programs and data when the power is off. Hard disk drives, solid state drives and optical discs are examples.
  2. RAM is volatile and loses its contents when the computer is switched off. Secondary storage keeps the operating system, programs and files permanently.
  3. Secondary storage is much slower to access than RAM. Secondary storage holds far more data for the same cost.
  4. A hard disk stores data on spinning platters coated in magnetic material. A read/write head magnetises tiny areas in one of two directions to represent 1s and 0s.
  5. A hard disk must spin its platters and move its head to the right place before reading. A solid state drive has no moving parts, so data is reached almost instantly.
  6. Magnetic hard disks offer very large capacities at a low cost per gigabyte. Hard disks suit servers and backups that hold large amounts of data.
  7. An optical disc stores data as a spiral track of tiny pits and flat areas called lands. A laser reads the disc by detecting how light reflects from the surface.
  8. A Blu-ray drive uses a blue-violet laser with a shorter wavelength than a DVD's red laser. The pits can be smaller and packed more closely together.
  9. Optical discs are cheap to produce and light to post. Optical discs have small capacities and slow access, and they scratch easily.
35
Issues and ImpactQuestions
Issues and Impact
Environmental impact of digital devices
  1. What environmental issues are linked to digital devices?
  2. Why does the energy consumption of digital devices matter?
  3. How can the energy used by a device be reduced?
  4. Why do data centres consume so much energy?
  5. How does manufacturing digital devices harm the environment?
  6. Why are rare earth elements an environmental concern?
  7. What is the replacement cycle of a digital device?
  8. Why do short replacement cycles harm the environment?
  9. Why do people replace devices before they stop working?
56
Issues and ImpactAnswers
Answers
Environmental impact of digital devices
  1. Devices affect the environment through the energy they use, the materials needed to make them and the way they are thrown away. Frequent replacement makes each of these worse.
  2. Devices, networks and data centres use large amounts of electricity. Much of that electricity still comes from fossil fuels, which release carbon dioxide.
  3. Devices can use power-saving modes and switch off when idle. Energy-efficient processors and screens also use less electricity.
  4. Data centres run thousands of servers day and night. The servers give off heat, so powerful cooling systems are needed as well.
  5. Metals such as cobalt, lithium and gold must be mined, which damages land and uses large amounts of water and energy. Factories also release carbon dioxide and other pollution.
  6. Rare earth elements are needed for parts such as magnets, speakers and screens. Extracting them produces toxic waste that can pollute soil and water.
  7. The replacement cycle is how often people replace a device with a newer model. Many people replace their phones every two or three years.
  8. Every new device needs more raw materials and energy to make. The old device often ends up as waste.
  9. New models offer better features, and advertising encourages people to upgrade. Some older devices also stop receiving software updates.
57
Keep going
680
questions
41 subtopics

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680 questions
Across 41 subtopics, every one of them from specification 1CP2.
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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