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This document discusses different types of computer memory and storage devices. It describes primary memory such as RAM and ROM that are directly accessible by the CPU. RAM is volatile and comes in DRAM and SRAM varieties, while ROM is non-volatile and includes PROM, EPROM, and EEPROM. Secondary storage devices include magnetic hard disks and optical disks that are non-volatile and used for long-term storage. Common storage media include floppy disks, CDs, DVDs, magnetic tapes, and flash memory that is used in devices like cameras, phones, and computers.
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- 2. Memory types • Primary Memory(eg.RAM,ROM) • Secondary Memory(eg.Hard disk)
- 3. Primary Memory • It is the only memory that is directly accessible to CPU. The CPU continuously reads instructions stored there and executes them as required. • Various "Primary storage devices" are: • RAM • ROM • Cache Memory
- 4. RAM(Random Access Memory) • Random Access Memory allows stored data to be accessed directly in any random order. It is a Volatile Memory i e the data vanishes when the power supply is cut off. • These are of 2 types: SRAM DRAM
- 5. DRAM (Dynamic random access memory) • This is a Random Access Memory that stores each bit of data in a separate capacitor. The capacitor can be either charged or discharged; these two states are taken to represent the two values of bit, that are 0 and 1. • This memory needs to be refreshed periodically
- 6. SRAM (Static Random Access Memory) • It is faster than the DRAM as it uses a six transistor configuration. In this the direction of current depicts the value 0 or 1. • It is expensive than DRAM • This memory need not to be refreshed frequently.
- 7. ROM(Read Only Memory) • The DATA stored in Read Only Memory cannot be modified or can be modified only slowly or with difficulty. • It is non-volatile memory i e it does not loose data when the power is cut off. • Its various types are : PROM EPROM EEPROM
- 8. PROM (Programmable Read Only Memory) • On Programmable Read Only Memory the Data can be written only once. • It is Manufactured as a blank memory and then the data is written on it ,also called as Burning the PROM.
- 9. EPROM (Erasable Programmable read Only Memory) It is a special type of ROM that retains its contents until it is exposed to ultraviolet light. The ultraviolet light clears its contents , makes it possible to reprogram the memory.
- 10. EEPROM (Electrically Erasable Programmable Read Only Memory) • EEPROM is a special type of PROM that can be erased by exposing it to an electric charge. Like other RAM it retains its memory even if the power is switched off. • Data is written or erased one byte at a time
- 11. Flash Memory Flash Memory is a special type of EEPROM that can be erased and reprogrammed in blocks instead of one byte at a time. Many modern PC's have their BIOS stored on a flash memory chip so that it can be easily updated if necessary.
- 12. Secondary Memory • Secondary storage does not lose the data when the device is powered down—it is non- volatile. Per unit, it is typically also an order of magnitude less expensive than primary storage. • Two Types of secondary storage devices are: Magnetic storage devices Optical storage devices
- 13. Magnetic Storage Devices Various Magnetic Storage Devices are: Floppy Disk Hard Disk High Capacity Floppy Disc Magnetic Tape
- 14. Optical storage devices Various Optical storage devices are : •Compact disk Read Only Memory (CD-ROM) •Digital Video Disk Read Only Memory (DVD- ROM) •CD-Recordable(CD-R) •CD-Rewritable(CD-RW)
- 15. Memory is used in • Computer • Mobile • Printer • Digital Camera • CD/DVD Players • Many other appliances like TV, Washing machine, Digital Diaries etc.
- 16. THANKS