2.1: Primary Storage (Memory)
Exam Board:
Cambridge OCR
Specification:
GCSE - J277
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Primary Storage
What primary storage (memory) is and why computers have it.
The key characteristics of Random Access Memory (RAM) and Read-Only Memory (ROM).
Why computers may use virtual memory and how it works.
What You Need to Know
Primary Storage
Primary storage is high-speed, internal memory that the CPU can directly access. It includes RAM and ROM.
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Primary storage is needed to provide fast, direct access to the data and instructions required to run programs and start the computer.
Random Access Memory (RAM)
Read-Only
Memory (ROM)
RAM is volatile. This means that data is lost when the power is turned off.
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RAM temporarily stores the instructions and data for programs that are currently running. It also stores parts of the operating system currently in use.
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​​The contents of RAM can be changed. Data can be written to RAM and also read from it.
ROM is non-volatile. This means that data is saved even when the power is turned off.
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​ROM stores the start-up instructions used to boot the computer and load the operating system. It also stores firmware, such as the BIOS, to check that hardware components are functioning correctly during start-up.
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​ROM is read-only, meaning the contents cannot be changed and can only be viewed.
Virtual Memory
When RAM is close to full capacity, parts of programs not currently needed can be temporarily moved to a section of secondary storage called virtual memory.
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When required again, data is moved from virtual memory back into RAM, allowing more programs to run at once without running out of memory. However, virtual memory is much slower than RAM, and excessive use can cause thrashing, significantly reducing performance.
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Questo's Questions
2.1 - Primary Storage (Memory):
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​1. Explain why the computer requires primary storage. [2]
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2. For each type of memory below, describe it and state what information is stored within it:
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a. Random Access Memory (RAM) [3]
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b. Read-Only Memory (ROM) [3]
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c. Virtual memory [3]