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A computer stores images online - Edexcel - GCSE Computer Science - Question 6 - 2019 - Paper 1
Question 6
A computer stores images online. (a) An image uses 8-bit colour and is 64 pixels wide. It uses 1MB of storage. Construct an expression to calculate the height of th... show full transcript
Worked Solution & Example Answer:A computer stores images online - Edexcel - GCSE Computer Science - Question 6 - 2019 - Paper 1
Step 1
Construct an expression to calculate the height of the image in pixels.
Answer
To determine the height of the image in pixels, we can use the formula for calculating the size of the image in bytes based on its dimensions and color depth.
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Calculate the total number of bits used for the image:
Total bits = Width in pixels × Height in pixels × Bits per pixel
The width is given as 64 pixels and the color depth is 8 bits.
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Convert 1MB into bytes:
1 MB = 1024 KB = 1024 × 1024 bytes = 1,048,576 bytes
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Set up the equation:
1,048,576 bytes = 64 pixels × Height in pixels × (8 bits / 8)
Simplifying gives us:
1,048,576 = 64 × Height
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Thus, we can express the height in pixels as:
Height in pixels = \frac{1,048,576}{64}
This represents our complete expression to calculate the height in pixels based on the storage requirement.
Step 2
Describe how the operating system uses virtual memory to manage the situation.
Answer
When the computer runs multiple applications simultaneously, the total memory required by these applications can exceed the available physical memory (RAM). To handle this situation, the operating system employs virtual memory management, which works as follows:
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Page Swapping: The operating system divides the memory into blocks, known as pages. When physical memory becomes full, it can swap certain pages from RAM to a reserved space on the hard drive, known as the swap space or page file.
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Transparent to Applications: Applications are unaware of this swapping process. The operating system keeps track of which pages are in physical memory and which are stored on the hard drive, ensuring seamless access to data.
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Efficient Memory Usage: By using disk space to simulate additional memory, the operating system allows multiple applications to run concurrently, even when their combined memory needs surpass physical RAM.
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Performance Considerations: While virtual memory enables running more applications, accessing data from disk is considerably slower than from RAM. As such, the operating system manages page replacement algorithms to optimize performance and responsivity.