Storage Devices - Computer Memory PDF

**Storages devices** The storage unit is a part of the computer system which is employed to store the information and instructions to be processed. A storage device is an integral part of the computer hardware which stores information/data to process the result of any computational work. Without a...

**Storages devices** The storage unit is a part of the computer system which is employed to store the information and instructions to be processed. A storage device is an integral part of the computer hardware which stores information/data to process the result of any computational work. Without a storage device, a computer would not be able to run or even boot up. Or in other words, we can say that a storage device is hardware that is used for storing, porting, or extracting data files. It can also store information/data both temporarily and permanently.  **Types of Computer Memory** **1. Primary Memory:** It is also known as internal memory and main memory. This is a section of the CPU that holds program instructions, input data, and intermediate results. It is generally smaller in size. RAM (Random Access Memory) and ROM (Read Only Memory) are examples of primary storage. **2. Secondary Memory: **Secondary storage is a memory that is stored external to the computer.  It is mainly used for the permanent and long-term storage of programs and data. Hard Disks, CDs, DVDs, Pen/Flash drives, SSD, etc, are examples of secondary storage. **1. Primary Storage Devices** - **RAM: **It stands for Random access memory. It is used to store information that is used immediately or we can say that it is a temporary memory. Computers bring the software installed on a hard disk to RAM to process it and to be used by the user. Once, the computer is turned off, the data is deleted. With the help of RAM, computers can perform multiple tasks like loading applications, browsing the web, editing a spreadsheet, experiencing the newest game, etc. It allows you to modify quickly among these tasks, remembering where you're in one task once you switch to a different task. It is also used to load and run applications, like your spreadsheet program, answers commands, like all edits you made within the spreadsheet, or toggle between multiple programs, like once you left the spreadsheet to see the email. Memory is nearly always actively employed by your computer. It ranges from 1GB -- 32GB/64GB depending upon the specifications. There are different types of RAMS, and although they all serve the same purpose, the most common ones are:  - **SRAM: **It stands for Static Random Access Memory. It consists of circuits that retain stored information as long as the power supply is on. It is also known as volatile memory. It is used to build Cache memory. The access time of SRAM is lower and it is much faster as compared to DRAM but in terms of cost, it is costly as compared to DRAM. - **DRAM: **It stands for Dynamic Random Access Memory. It is used to store binary bits in the form of electrical charges that are applied to capacitors. The access time of DRAM is slower as compared to SRAM but it is cheaper than SRAM and has a high packaging density. - **ROM: **It stands for Read Only Memory. The data written or stored in these devices are non-volatile, i.e., once the data is stored in the memory cannot be modified or deleted. The memory from which will only read but cannot write it. This type of memory is non-volatile. The information is stored permanently during manufacture only once. ROM stores instructions that are used to start a computer. This operation is referred to as bootstrap. It is also used in other electronic items like washers and microwaves. ROM chips can only store a few megabytes (MB) of data, which ranges between 4 and 8 MB per ROM chip. There are two types of ROM:  - **PROM: **PROM is Programmable Read Only Memory. These are ROMs that can be programmed. A special PROM programmer is employed to enter the program on the PROM. Once the chip has been programmed, information on the PROM can't be altered. PROM is non-volatile, that is data is not lost when power is switched off. - **EPROM:** Another sort of memory is the Erasable Programmable Read-Only Memory. It is possible to erase the info which has been previously stored on an EPROM and write new data onto the chip. - **EEPROM:** EEPROM is Electrically erasable programmable read-only memory. Here, data can be erased without using ultraviolet light, with the use of just applying the electric field. ### Characteristics of Secondary Memory - These are magnetic and optical memories. - It is known as the backup memory. - It is a non-volatile memory. - Data is permanently stored even if power is switched off. - It is used for storage of data in a computer. - Computer may run without the secondary memory. - Slower than primary memories A hard disk is also known as a hard drive or fixed disk. It is said to be rigid magnetic disc that stores data. It is located within a drive unit. Hard disk is a non-volatile storage device that contains platters and magnetic disks rotating at high speeds. Non-volatile means the data retains when the computer shuts down. It is installed internally in our computer systems. Hard disk is located within a drive unit on the computer\'s motherboard and comprises one or more platters packed in an air-sealed casing. Its main components include a read/write actuator arm, head actuator, read/write head, spindle, and platter. A circuit board (also called as the interface board or disk controller) is present on the back of a hard drive. It lets the hard drive to communicate with the computer. The advantages of a Hard Disk are given as follows: - One of the significant advantages of a Hard Disk drive is that its cost is low. - Another advantage of a Hard Disk is that it is readily available in the market. - Hard Disk is faster than optical disks. - The capacity for storing the data in HDDs is large. **Optical Disk:**  An optical disk is any computer disk that uses optical storage techniques and technology to read and write data. It is a computer storage disk that stores data digitally and uses laser beams to read and write data. i. **CD-ROM:** It stands for Compact Disk-Read Only Memory. The manufacturer writes the data on these CDs. Furthermore, the user can only read this data and it cannot be changed. Basically, such disks contain games, audios, videos, application software, etc. for release in the market. ii. **CD-R:** It stands for Compact Disk-Recordable. The user can write data on these disks. But he cannot erase or change the data later. iii. **CD-RW: **It stands for Compact Disk-Rewritable. The user can write and delete data on these disks as many times as he requires. **DVD (DIGITAL VERSATILE DISK)** These disks have a much larger storage capacity than CDs. Moreover, they store multimedia files that require high storage space. Furthermore, its storage capacity ranges from 4.7GB to 17GB. Besides, we can also call it **digital versatile disk**. It is also of three types: - - - **Pen Drive:** It is also known as a USB flash drive that includes flash memory with an integrated USB interface. We can directly connect these devices to our computers and laptops and read/write data into them in a much faster and more efficient way. These devices are very portable. It ranges from 1GB to 256GB generally. - **SSD: **It stands for solid state drive, a mass storage device like HDD. It is more durable because it does not contain optical disks inside like hard disks. It needs less power as compared to hard disks, is lightweight, and has 10x faster read and writes speed as compared to hard disks. But these are costly as well. While SSDs serve an equivalent function as hard drives, their internal components are much different. Unlike hard drives, SSDs don't have any moving parts and thus they're called solid-state drives. Instead of storing data on magnetic platters, SSDs store data using non-volatile storage. Since SSDs haven't any moving parts, they do not need to "spin up". It ranges from 150GB to a few more TB. - **SD Card: **It is known as a Secure Digital Card. It is generally used with electronic devices like phones, digital cameras, etc. to store larger data. It is portable and the size of the SD card is also small so that it can easily fit into electronic devices. It is available in different sizes like 2GB, 4GB, 8GB, etc. - **Memory Card: **It is generally used in digital cameras. printers, game consoles, etc. It is also used to store large amounts of data and is available in different sizes. To run a memory card on a computer you require a separate memory card reader.