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Comp App Lect 3.pptx

The document discusses different types of computer memory. It defines memory as the component that stores instructions and data. There are two main types of memory: primary memory (RAM) that is directly accessed by the CPU, and secondary memory like hard disks. RAM is volatile and temporarily stores data during use, while ROM is non-volatile and stores permanent instructions. The document outlines different RAM technologies like DRAM, SRAM, and MRAM and compares their characteristics. It also discusses cache memory, ROM, flash memory, and CMOS memory.

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1 Memory A component in the computer used for storing instructions and data is called memory. Ms-Nazia
3 Types Memory  Memory can be divided into two types.  Primary memory  Secondary memory
Primary Memory  Primary memory is computer memory that is accessed directly by the CPU. This includes several types of memory, such as the processor cache and system ROM. ... RAM, or random access memory, consists of one or more memory modules that temporarily store data while a computer is running.
5 Types of Memory  There are two types of memory in computer that are as follows:  Volatile Memory: It loses its contents when computer is turned off. RAM is the most common type of volatile memory  Non-volatile Memory: It does not lose its contents when computer is turned off. ROM, Flash memory and CMOs are examples of non-volatile memory.
6 RAM  RAM stands for Random Access Memory also called direct access memory.  Random-access memory (RAM) is a form of computer data storage that stores data and machine code currently being used. A random-access memory device allows data items to be read or written in almost the same amount of time.  Random access means that each individual byte in entire memory can be accessed directly.  RAM is a volatile memory. It means that its contents are lost when the power is turned off.  RAM is read/write memory.  CPU can read data from RAM and write data to RAM. It is used to store data and instructions while it is being executed.  RAM is also called main memory or primary memory
7 RAM  RAM plays very important role in the processing speed of computer.  A bigger RAM size provides larger amount of space for processing. So the processing speed is increased. The amount of data that can be stored in RAM is measured in bytes.  Most desktop computers typically have up to 2GB of RAM. It also allows the addition of more memory if need.
8 Types Of RAM  RAM is built by two different techniques: 1. DRAM 2. SRAM 3. MRAM
9 DRAM  DRAM stands for Dynamic Random Access Memory. It is a type of memory that is used in most computers. It is least expensive type of RAM.  DRAM requires electric current to maintain its electrical state.  The electrical charge of DRAM decreases with time that may result in loss of data.  DRAM is recharged and refreshed again and again to maintain its data. The processor cannot accessed the data of DRAM when it is being refreshed. That is why it is slow.
DRAM  Dynamic random-access memory (DRAM) is a type of memory that stores each bit of data in a separate tiny capacitor within an integrated circuit.  The capacitor can either be charged or discharged; these two states are taken to represent the two values of a bit, conventionally called 0 and 1.  The electric charge on the capacitors slowly leaks off, so without intervention the data on the chip would soon be lost. To prevent this, DRAM requires an external memory refresh circuit which periodically rewrites the data in the capacitors, restoring them to their original charge.  Because of this refresh requirement, it is dynamic memory as opposed to static random-access memory (SRAM) which does not require data to be refreshed.  DRAM is volatile memory, since it loses its data quickly when power is removed.
SRAM  SRAM stands for Static Random Access Memory.  SRAM that retains data bits in its memory as long as power is being supplied.  Unlike dynamic RAM, it does not need to be refreshed.  While SRAM can operate at higher speeds than DRAM, it is more expensive to manufacture because of its complex internal structure, so most of the RAM on the motherboard is DRAM.  SRAM is most often found in hard drives. It is also found in compact discs (CD’s), printers, modem routers, digital versatile discs (DVD’s) and digital cameras.
12 SRAM  It can store data without any need of frequent recharging. CPU does not need to wait to access data from SRAM during the processing. That is why it is faster than DRAM.  It utilizes less power than DRAM.  SRAM is more expensive.  It is normally used to build a very fast memory known as cache memory.
13 MRAM  MRAM stands for Megnetoresistive Random Access Memory.  It can store data using magnetic charges instead of electrical charges.  MRAM uses far less power than other RAM technologies that make it ideal of portable computing devices.  It also has greater storage capacity.  It has faster access time than RAM.  It utilizes less power than DRAM.  It retains its contents when the power is removed from computer.
14 Difference Between SRAM & DRAM  The difference between SRAM and DRAM is as follows: S.# SRAM DRAM 1. It is faster than DRAM It is slower than DRAM 2. It is more expensive It is less expensive 3. It does not need to be power refreshed It has to be refreshed after each read operation 4. It utilizes less power It utilizes more power 5. It holds data indefinitely(unlimited period of time) as long as the computer is turned on It holds data dynamically(powerful) not indefinitely 6. It is more complex and less compact(compress) It is less complex and more compact
15 ROM  ROM stands for read only memory. The instructions in ROM prepare the computer for use. These instructions can only be read but cannot be changed or deleted.  It is not possible to write new information or instructions into the ROM.  ROM stores data and instructions permanently. When the computer is switched off, the instructions stored in the ROM are not lost . Therefor, ROM is called non-volatile memory.  The information in ROM is stored by the manufacturer. When the computer is switched on, the instructions in the ROM is automatically loaded into the memory of the computer.
16 ROM  ROM contains the small set of instructions called ROM BIOS.  BIOS stands for Basic Input / Output System. These instructions tell the computer how to access hard disk, find operating system and load in it RAM.  Once data has been written onto a ROM chip, it cannot be removed and can only be read. Unlike main memory (RAM),ROM retains its contents even when the computer is turned off. ROM is referred to as being nonvolatile, whereas RAM is volatile.
17 Types of ROM  Different types of ROM are as follows: 1. PROM (Programmable Read Only Memory) 2. EPROM (Erasable Programmable Read Only Memory) 3. EEPOM (Electronically Erasable Programmable Read Only Memory)
18 PROM  PROM stands for programmable Read Only Memory. This form of ROM is initially blank. The user and manufacturer can write data and program on it using special device.  The user can write data and instructions only once. If there is any error in writing the instruction, the error cannot be removed from PROM. The chip becomes unusable.
19 EPROM  EPROM stands for Erasable Read Only Memory. This form of ROM is initially blank. The user and manufacturer can write data and program on it using special device.  The data and programs written on it can be erased with special devices using ultraviolet rays. The user can write new program on it.  EPROM can be erased by exposing it to ultra-violet light for a duration of up to 40 minutes. Usually, an EPROM eraser achieves this function.
20 EEPROM  EEPROM stands for Electronically Erasable Programmable Read Only Memory.  In this memory, user can erase and write instructions with the help of electrical pulses.  If there is any error in writing the instructions, the user can erase the contents electronically. The contents of EEPROM can be modified easily.  EEPROM is programmed and erased electrically. It can be erased and reprogrammed about ten thousand times. Both erasing and programming take about 4 to 10 ms (millisecond).
21 Difference Between PROM & EPROM  The difference between PROM and EPROM is as follows: S.# PROM EPROM 1. PROM is programmable read only memory EPROM is erasable programmable read only memory 2. The user can write instructions on PROM only once The user can write instructions many times on EPROM 3. The instructions written by the user can not be erased from PROM The instructions written by the user can be erased from EPROM 4. If there is an error while writing on PROM, it becomes unusable. If there is an error while writing on EPROM, it becomes usable. 5. It provides less usability as instructions are written only once. It provides more usability as instructions are written many times.
22 Difference Between RAM & ROM  The difference between RAM and ROM is as follows: S.# RAM ROM 1. RAM is a temporary memory. ROM is a permanent memory. 2. RAM enables data to be both read and written to memory or data can be changed or deleted. The instructions written in ROM can only be read but cannot be changed or deleted 3. Instructions in the RAM is continuously changing as different programs are executed and new data are processed. It is not possible to write new information or new instructions into the ROM, so ROM is non-volatile memory. 4. When the power is turned off, all the programs and data are erased from RAM. Therefore, RAM is a volatile memory. When the power is turned off, the instructions stored in ROM are not lost, therefore ROM is non-volatile memory 5. The instructions are written into RAM at the time of execution. The instructions are written into ROM at manufacturing time.
23 Cache Memory  A cache (pronounced Cash) is a small very fast memory. It is designed to speed up the transfer of data and instructions. It is located inside or close to the CPU chip. It is more expensive and faster than RAM.  The data and instructions that are recently or most frequently used by CPU are stored in cache.  The data and instructions are retrieved from RAM when CPU uses them for first time. A copy of that data or instructions is stored in cache. The next time the CPU needs that data or instructions, it first looks in cache.  If the required data is found there, it is retrieved from cache memory instead of main memory. It speeds up the working of CPU.
24 Flash Memory  Flash memory is a type of non-volatile memory. It can be erased electronically like EEPROM.  Most computer use it to store startup instructions as it allows computer to update its contents easily.  Flash memory chips also stores data and programs on mobile computer and other devices such as smart phone, portable media players, printers and digital cameras etc.  The data in smart phones are used on flash memory. Some portable media players store music on flash memory chips.
Flash Memory  Flash memory is a non-volatile memory chip used for storage and for transfering data between a personal computer (PC) and digital devices. It has the ability to be electronically reprogrammed and erased. It is often found in USB flash drives, MP3 players, digital cameras and solid-state drives.  Flash memory is a type of electronically erasable programmable read only memory (EEPROM), but may also be a standalone memory storage device such as a USB drive. EEPROM is a type of data memory device using an electronic device to erase or write digital data.
26 CMOS  CMOS stands for Complementary Metal-Oxide Semiconductor.  CMOS technology provides high speed and consumes less power.  It stores configuration information of computer. The information include the types of disk drives, keyboard and monitor, current date & time and other startup information required during boating process.  CMOS chip uses battery to retain information even when the computer is turned off.  The information in CMOS can be changed.
 CMOS (complementary metal-oxide-semiconductor) is the term usually used to describe the small amount of memory on a computer motherboard that stores the BIOS settings. Some of these BIOS settings include the system time and date as well as hardware settings. 