Physical storage devices What is a storage device

Physical storage devices

What is a storage device? • Stores data from storage media • Hardware that holds information either permanently or temporarily

Characteristics of storage devices • Primary storage devices – smaller in size, temporarily stores data, volatile and are internal forms of storage. • Secondary storage devices- stores large amounts of data permanently. • Secondary storage devices can be removable, internal or external storage.

Characteristics of storage devices • Volatile vs. non-volatile • Volatile – data can be lost in case of power failure • Non-volatile – saved data can be kept if there is a power failure. • Random vs. Sequential • Random access- data can be obtained from anywhere on the storage medium • Sequential access – data can be obtained in the order in which it was stored

Types of memory Random Access Memory (RAM) • • Primary memory Very fast (direct access to CPU) Volatile Expensive Read Only Memory (ROM) • Non- volatile memory • Data is permanently written and cannot be altered.

Magnetic storage devices • Represents information by using magnetic patterns • Secondary storage floppy • A disk can store over 10 gigabytes • Types of magnetic storage devices: Ø Magnetic tape – used to store large amounts of data, serial access. Ø Hard drive – very large storage capacity (1 TB), random access. Transfer large amounts of data from computer to computer. Ø Floppy disc – low capacity, portable, random access. Used to transfer small amounts of data Ø Zip disc – stores a higher capacity than floppy disc tape

Optical storage discs • Uses lasers and lights to read and write data • The discs are divided into sectors and use a single spiral track • Forms of optical discs: Ø CD-ROM – data can only be read but not altered Ø WORM – write once, read many Ø Erasable optical – can be read, written and erased. • Categories of disc: CD, DVD and Blu-ray Ø CD-ROM disc – non-volatile, random access, stores software, music etc. Ø DVD-ROM – random access, stores more data than CD-ROM Ø CD-RW and DVD-RW- rewritable discs, data can be altered Ø CD-R and DVD-R – data can be burnt onto discs but not removed Ø Blu-ray disc – random access, stores more data than DVD-ROM, stores HD-videos

Flash Memory • Electronic chips that stores data • The information can be altered, accessed and erased • Flash memory is known as solid state hard drives and it is nonvolatile • Types of flash memory: Ø Embedded flash memory chips are placed in devices such as digital cameras and mobile phones. Ø Flash memory cards have one or more memory chips Ø USB flash drive – small, portable device that includes flash memory, they plug into USB ports and store files in a variety of formats.

Summary • Storage devices can be classified by: 1. Volatility 2. Random access vs Sequential access 3. Primary or secondary • Types of storage devices: 1. Magnetic discs 2. Optical discs 3. Flash memory

References • Computer Hope. 2018. Storage Devices. https: //www. computerhope. com/jargon/s/stordevi. htm • Viescas, Amber. 2015. What Are the Characteristics of Storage Devices? Techwalla. https: //www. techwalla. com/articles/whatare-the-characteristics-of-storage-devices