Memory and its Types.ppt
- 1. Memory and its Types Dr. Ghayoor Abbas Bhatti Lecturer BS(H)Computer Science, MHPED, BHPED, M.A Sociology CPEHSS UoS, Jamshoro
- 3. Memory Types I. Secondary Memory II.Primary Memory a)RAM i. SRAM ii. DRAM b)ROM i. PROM ii. EPROM c)Hybrid i. EEPROM ii. NVRAM iii. Flash Memory d)Cache Memory e)Virtual Memory
- 4. What is Memory? • Computer memory is any physical device capable of storing information temporarily or permanently. For example, Random Access Memory (RAM), is a type of volatile memory that is stores information on an integrated circuit, and that is used by the operating system, software, hardware, or the user.
- 5. Volatile vs. non-volatile memory • Memory can be either volatile and non- volatile memory. Volatile memory is a temporary memory that loses its contents when the computer or hardware device loses power. Computer RAM is a good example of a volatile memory and is why if your computer freezes or reboots when working on a program you lose anything that hasn't been saved.
- 6. Volatile and non-Volatile • Non-volatile memory, sometimes abbreviated as NVRAM, is memory that keeps its contents even if the power is lost. EPROM is a good example of a non-volatile memory.
- 7. Memory is not disk storage • It is very common for new computer users to be confused by what parts in the computer are memory. Although both the hard drive and RAM are considered memory, it is more appropriate to refer to RAM as "memory" or "primary memory" and a hard drive as "storage" or "secondary storage" and not memory.
- 8. Memory is not disk Storage • When someone asks how much memory is in your computer, it is likely between 1GB and 8GB of Random Access Memory (RAM) and several hundred Gigs of hard disk drive memory (storage). In other words, You will almost always have more hard drive space than RAM.
- 9. Primary Memory (Main Memory) • Primary Memory RAM ROM Semiconductor Definition: • A device for storing digital information that is fabricated by using integrated circuit technology. Also known as integrated-circuit memory; large-scale integrated memory; memory chip; semiconductor storage; transistor memory.
- 10. Characteristic of Main Memory • These are semiconductor memories. • It is known as main memory. • Usually volatile memory. • Data is lost in case power is switched off. • It is working memory of the computer. • Faster than secondary memories. • A computer cannot run without primary memory.
- 11. RAM
- 12. RAM • RAM is of two types: • Static RAM (SRAM) • Dynamic RAM (DRAM) SRAM is a type of RAM that stores data using a static method, in which the data remains constant as long as electric power is supplied to the memory chip. This is different than DRAM (dynamic RAM), which stores data dynamically and constantly needs to refresh the data stored in the memory. Because SRAM stores data statically, it is faster and requires less power than DRAM.
- 13. Dynamic RAM (DRAM) • Characteristics of the Dynamic RAM: • It has short data lifetime • Need to refresh continuously • Slower as compared to SRAM • Used as RAM • Lesser in size • Less expensive • Less power consumption
- 14. ROM
- 15. ROM • ROM stands for Read Only Memory. It is type of internal memory. The data and instructions in ROM are stored by the manufacturer at the time of its manufacturing. This data and programs cannot be changed or deleted after wards. The data or instructions stored in ROM can only be read but new data or instructions cannot be written into it. This is the reason why it is called Read Only Memory. ROM stores data and instructions permanently. When the power is turned off, the instructions stored in ROM are not lost. That is the reason ROM is called non-volatile memory.
- 16. Types Of ROM ROM is divided into following types: • PROM • EPROM • EEPROM
- 17. PROM PROM stands for Programmable Read Only Memory. This form of ROM is initially blank. The user or manufacturer can write data/program on it by using special devices. However, once the program or data is written in PROM chip, it cannot be changed. If there is an error in writing instructions or data in PROM, the error cannot be erased. PROM chip becomes unusable.
- 18. EPROM EPROM stands for Erasable Programmable Read Only Memory. This form of ROM is also initially blank. The user or manufacturer can write program or data on it by using special devices. Unlike PROM, the data written in EPROM chip can be erased by using special devices and ultraviolet rays. So program or data written in EPROM chip can be changed and new data can also be added. When EPROM is in use, its contents can only be read.
- 19. EEPROM EEPROM stands for Electrically Erasable Programmable Read Only Memory. This kind of ROM can be written or changed with the help of electrical devices. So data stored in this type of ROM chip can be easily modified.
- 20. Hybrid types As memory technology has matured in recent years, the line between RAM and ROM has blurred. Now, several types of memory combine features of both. These devices do not belong to either group and can be collectively referred to as hybrid memory devices. Hybrid memories can be read and written as desired, like RAM, but maintain their contents without electrical power, just like ROM. Two of the hybrid devices, EEPROM and flash, are descendants of ROM devices. These are typically used to store code. The third hybrid, NVRAM, is a modified version of SRAM. NVRAM usually holds persistent data.
Editor's Notes
- #13: Static RAM is used as cache memory needs to be very fast and small. Characteristics of the Static RAM: It has long data lifetime There is no need to refresh Faster Used as cache memory Large size Expensive High power consumption