Computer Memory and Storage Devices

Department of Computer Application- COMPUTER Memory and Storage Devices
PRIMARY MEMORY
RAM AND ROM
RAM: random access memory
DRAM: dynamic RAM
SDRAM (Synchronous DRAM)
PROM: programmable ROM
EEPROM: electronically EPROM

1. BBA(Gen) Computer Fundamentals (17107) Bharti Dewani Assistant Professor,IT

2. COMPUTER Memory and Storage Devices

3. PRIMARY MEMORY: RAM AND ROM RAM (Random Access Memory) is volatile (temporary). Programs and data can be written to and erased from RAM as needed. This means that RAM does not retain its bit configuration when the power is turned off, but ROM does ROM ( Read Only Memory) is nonvolatile (permanent). The contents in locations in ROM cannot be changed It holds instructions that run the computer when it is first turned on (BIOS) The CPU accesses each location in memory by using a unique number, called a memory address.

4. Memory types- RAM RAM: random access memory SRAM: static RAM No need to be refreshed DRAM: dynamic RAM Need to be refreshed periodically Main memory SDRAM (Synchronous DRAM) EDRAM (Enhanced DRAM) EDO (Extended Data Out) FLASH RAM Ferroelectric RAM

5. Memory types– ROM ROM: read-only memory (Pre-programmed) PROM: programmable ROM Only written once EPROM: erasable PROM Use ultraviolet light to erase data EEPROM: electronically EPROM Can be erased using electronic impulses (higher voltages)

6. Secondary Storage Devices Storage devices hold data, even when the computer is turned off. The physical material that actually holds data is called a storage medium. The surface of a floppy disk is a storage medium . The hardware that writes data to or reads data from a storage medium is called a storage device. A floppy disk drive is a storage device. The two primary storage technologies are magnetic and optical.

7. Magnetic Storage Devices Diskettes (floppy disks) (FDD) Hard disks (HD) High-capacity floppy disks (ZIP Disk) USB flash drive Magnetic tape

8. Optical Storage Devices Compact Disk Read-Only Memory (CD-ROM) Digital Video Disk Read-Only Memory (DVD-ROM) CD-Recordable (CD-R) CD-Rewritable (CD-RW) PhotoCD

9. Magnetic Storage Devices How Magnetic Storage Works A magnetic disk's medium contains iron particles, which can be polarized—given a magnetic charge—in one of two directions (north or south). Each particle's direction represents a 1 (on) or 0 (off), representing each bit of data that the CPU can recognize. A disk drive uses read/write heads containing electromagnets to create magnetic charges on the medium.

10. Magnetic Storage As the medium rotates, the head writes the data

11. Magnetic Storage Devices - Diskettes Diskette drives, also known as floppy disk drives, read and write to diskettes (called floppy disks or floppies). In disks the areas to save data are organized as a set of concentric circles called Tracks. Floppy disks have 80 tracks. The disks are further divided into pie-slice Sectors. 300 rpm Diskettes size: 3.5-inch.

12. Formatted Diskette

13. Hard Disk Drive Purpose: Long-term, nonvolatile storage Large, inexpensive, slow level in the storage hierarchy Disk composition A magnetic disk consist of a collection of platters (1to 20 per disk) that rotate on a spindle. Disk surface divided into tracks (1000 to 4800 per platter). Tracks are divided into sectors (64 per track), which are the smallest unit that can be read or written. Up to 10,000 rpm

14. Hard Disk A read/write head travels across a spinning magnetic disk, retrieving or recording data

15. Optical Storage Devices How Optical Storage Works An optical disk is a high-capacity storage medium. An optical drive uses reflected light to read data. To store data, the disk's metal surface is covered with tiny dents (pits) and flat spots (lands), which cause light to be reflected differently. When an optical drive shines light into a pit, the light cannot be reflected back. This represents a bit value of 0 (off). A land reflects light back to its source, representing a bit value of 1 (on).

16. Optical Disk

17. Optical storage devices CD-ROM: compact disc ROM ( Read Only Memory) Capacity: 650MB CD-R: compact disc recordable CD-RW: compact disc rewritable DVD: digital versatile disc Capacity: 4.7GB – 17GB DVD-R DVD-RW (2 versions: + (plus) and – (dash)

18. DVD (Digital Versatile Disk) Allows up to 17 gigabytes of storage (from 4.7 GB to 17 GB). Compatible with older CD-ROM technology. The four versions of the DVD: