Exam Board:
OCR A-Level
1.3 - Input, Output & Storage
Specification:
Computer Science H446
Watch on YouTube:
Input & output devices
Secondary storage
RAM & ROM
Virtual storage
This topic covers the internal and external devices required to input data into computer systems, output from them and store data for both temporary and long-term use.
Input & Output Devices
Input devices, such as a keyboard, mouse, microphone or sensor, allow data to be entered into a computer system for processing. Input can be manual (e.g. typing on a keyboard) or automatic (e.g. a temperature sensor taking readings).
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Output devices, such as monitors, printers and speakers, present the results of processing in a form understandable to humans. Input and output are not limited to text - they may also be visual, audio or tactile (e.g. braille displays or printed paper).
Secondary Storage
Secondary storage is non-volatile storage used to permanently hold programs and data when not in use by the CPU. There are three types:
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Magnetic storage uses magnetised patterns on a disk or tape (e.g. hard disk drives or magnetic tape) to store large amounts of data for a low cost per gigabyte.
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Solid-state storage uses flash memory with no moving parts (e.g. SSDs and USB drives), making it very fast, durable and portable. Because there are no moving parts, it is the fastest to access data.
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Optical storage uses lasers to read and write data as pits and lands on a disc surface (e.g. CDs, DVDs, Blu-ray). Discs are cheap to mass produce, but they are not durable, slow to access and have a low capacity.
Primary Storage
Primary storage is low-capacity, internal storage that the CPU can directly access. There are two types:​
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Random Access Memory (RAM) is volatile storage that temporarily holds both programs and data currently in use, including the operating system. It can be read from and written to, but all contents are lost when the power is turned off.
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Read Only Memory (ROM) is non-volatile storage that normally cannot be changed. The contents of ROM are saved when the power is turned off. ROM stores the BIOS and firmware, including the instructions needed to boot the computer when it is switched on.
Virtual Storage
Virtual storage is the separation of logical storage from physical storage, such as when data is stored remotely and accessed over a network instead of being kept locally.
A common example is cloud storage, where data is held on remote servers and accessed via the internet. Benefits are that it is scalable, enables easy collaboration, provides automatic backup and saves local storage space. Drawbacks include that it relies on a stable internet connection, poses security risks and reduces user control over data.
Questo's Key Terms
Input & Output Devices
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Secondary Storage: Magnetic - Solid State - Optical
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Primary Storage: RAM - ROM
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Virtual Storage: Cloud storage
Did You Know?
The first commercial hard disk drive, the IBM 305 RAMAC (released in 1956), was the size of two fridges, weighed around a tonne, and stored just 5 MB of data - about the same as one .mp3 song.
