Memory and Storage | OCR GCSE Computer Science (J277)
Memory and Storage
- 143 questions
- 9 subtopics
- J277/01
- J277/01
Memory and Storage is examined in J277/01, Computer systems.
It covers RAM, ROM, cache and virtual memory, secondary storage: magnetic, optical and solid state, data units and storage capacity calculations, binary, denary and hexadecimal conversions, binary addition, overflow and binary shifts, character sets, ASCII and Unicode, bitmap images, colour depth and resolution, sound sampling, sample rate and bit depth and lossy and lossless compression.
Sample questions from Memory and Storage
Answer each one closed book first, then open the answer.
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RAM, ROM, cache and virtual memory
What does it mean to say that RAM is volatile?
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Volatile memory loses its contents when the power is switched off. RAM needs a constant power supply to keep its data. -
Secondary storage: magnetic, optical and solid state
What do capacity, speed and portability mean when comparing storage devices?
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Capacity is how much data a device can hold. Speed is how quickly data can be read and written. Portability is how easy a device is to carry around. -
Data units and storage capacity calculations
Is a kilobyte 1,000 bytes or 1,024 bytes?
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A kilobyte is 1,000 bytes, using the standard metric prefix. A value of 1,024 bytes is also widely used and accepted, because 1,024 is 2¹⁰. -
Binary, denary and hexadecimal conversions
Convert the binary number 01001101 to denary.
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The denary value is 77. The column values are 64 + 8 + 4 + 1 = 77. -
Binary addition, overflow and binary shifts
How can you tell that an 8-bit binary addition has overflowed?
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A 1 is carried out of the most significant bit column. The true total is then larger than 255. -
Character sets, ASCII and Unicode
Why is ASCII usually stored using 8 bits per character?
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Computers store data in whole bytes, so each 7-bit code is held in one byte. Extended ASCII uses all 8 bits to give 256 characters. -
Bitmap images, colour depth and resolution
What happens to image quality and file size when the colour depth is increased?
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More colours can be shown, so the image looks more realistic. The file size also increases, because each pixel needs more bits. -
Sound sampling, sample rate and bit depth
How many different amplitude values can a 16-bit sample store?
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A 16-bit sample can store 65,536 different values. The figure comes from 2¹⁶ = 65,536.
The 9 subtopics
One subtopic is one session. Work down the list.
| Subtopic | What it covers | Questions |
|---|---|---|
| RAM, ROM, cache and virtual memory | Primary storage, the purposes of RAM and ROM, volatile and non-volatile memory, cache and the speed ranking of storage, and how virtual memory works when RAM is full. | 16 |
| Secondary storage: magnetic, optical and solid state | Why secondary storage is needed, magnetic, optical and solid state storage, comparing capacity, speed, portability, durability and reliability, and choosing storage for cameras, backups and consoles. | 16 |
| Data units and storage capacity calculations | Bits, nibbles and bytes, units from kilobyte to petabyte, converting between them, fixed capacities, and worked storage calculations including text file sizes. | 16 |
| Binary, denary and hexadecimal conversions | Place values and the most and least significant bits, the 0 to 255 range, and worked conversions between binary, denary and hexadecimal with the method for each. | 16 |
| Binary addition, overflow and binary shifts | The rules for binary addition, worked additions, overflow errors and how to spot them, and left and right shifts with their effect as multiplication and division. | 16 |
| Character sets, ASCII and Unicode | How characters are stored, character sets and bits per character, ASCII and Unicode compared, ordered character codes worked from A = 65, and text file sizes. | 16 |
| Bitmap images, colour depth and resolution | Pixels, colour depth and resolution, how each affects quality and file size, the image file size formula with worked calculations, and why metadata is stored. | 16 |
| Sound sampling, sample rate and bit depth | How sound is sampled, sample rate, bit depth and duration, their effect on quality and file size, the sound file size formula, and worked calculations. | 16 |
| Lossy and lossless compression | Why files are compressed, lossy and lossless compression with their advantages and disadvantages, choosing the right type for spreadsheets, music and X-rays, and common file formats. | 15 |
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.
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Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
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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.
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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.
Nearby topics
OCR GCSE Computer Science Active Recall Guide
Every topic, not just this one. 740 questions with their answers.