Summary
Summary A-Level Computer Science-Storage Devices
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Notes on Storage Devices for OCR A-Level Computer Science.
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Two types of memory within a computer: RAM (Random Access Memory); stores OS, running programs and data currently being used, volatile, read
and write. Very fast.
ROM (Read Only Memory); bootup instructions-bootstrap- non-volatile, read only.
RAM:
When apps or programs loaded, copied into RAM from Secondary Storage (e.g. Hard Disk). Data used
with those programs also opened by copying them into RAM as working memory. RAM starts to fill up.
Virtual Memory:
Part of the hard drive used as an extension to RAM.
Primary and Secondary Storage:
Primary is volatile, usually refers to RAM. Secondary Storage is non-volatile: three types: Magnetic,
Optical and Solid-State.
Secondary Storage Factors:
Durability
Reliability
Portability
Capacity
Speed
Cost
Tracks, sectors and platters:
Concentric tracks made on magnetic disk. Spins at high speed: 3600-7200 rpm. Spinning platters read by
drive heads- data read or written as sector moves under head.
Company server data:
Hard disks have high capacity; fast read/write speeds, relatively cheap per TB.
Solid state drives:
Solid state media uses electrically programmable non-volatile flash memory. Very durable; less capacity
than hard disk; faster than hard disks; less power consumed; more portable and expensive.
USB Flash Drives:
Store up to 128Gb of data, prices at <£5.00, power protection, useful transferring data between
computers.
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