35 lines
1.2 KiB
Markdown
35 lines
1.2 KiB
Markdown
---
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title: What_is_memory
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tags: [memory]
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created: Friday, July 12, 2024
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---
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# What is memory ?
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## Why do we need memory?
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> A CPU is just an operator on memory. It reads its instructions and data from
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> the memory and writes back out to the memory. (Ward 2021)
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When a [CPU](CPU_architecture.md) executes a program, it needs a place to store
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the program's **instructions** and **related data**. This is the role of memory.
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## What is memory?
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The data that comprises a program is a series of bits. The basic unit of memory
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storage is a **memory cell**: a circuit that can store a single bit.
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## Memory types
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There are two types of memory: [SRAM and DRAM](./DRAM_and_SRAM_memory.md). Both
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types of RAM memory are _volatile_ : the memory is only retained whilst the
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computer has a power supply and is wiped when the computer is rebooted. This
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contrasts with the memory of the harddisk which is non-volatile and is retained
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after a reboot.
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Programs that are executing are loaded into memory because the chips that
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comprise memory can read and store data much faster than the harddisk. It would
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be possible to run a program from the harddisk but it would be 500 - 1000 times
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slower than memory.
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## Related notes
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