Memory

The computer memory holds the data and instructions needed to process raw data and produce output. The computer memory is divided into large number of small parts known as cells. Each cell has a unique address which varies from 0 to memory size minus one.n computing, memory is a device or system that is used to store information for immediate use in a computer or related computer hardware and digital electronic devices. The term memory is often synonymous with the term primary storage or main memory. An archaic synonym for memory is store. Computer memory operates at a high speed compared to storage that is slower but less expensive and higher in capacity. Besides storing opened programs, computer memory serves as disk cache and write buffer to improve both reading and writing performance. Operating systems borrow RAM capacity for caching so long as not needed by running software.If needed, contents of the computer memory can be transferred to storage; a common way of doing this is through a memory management technique called virtual memory.



Modern memory is implemented as semiconductor memory, where data is stored within memory cells built from MOS transistors and other components on an integrated circuit. There are two main kinds of semiconductor memory, volatile and non-volatile. Examples of non-volatile memory are flash memory and ROM, PROM, EPROM and EEPROM memory. Examples of volatile memory are dynamic random-access memory (DRAM) used for primary storage, and static random-access memory (SRAM) used for CPU cache.Most semiconductor memory is organized into memory cells each storing one bit (0 or 1). Flash memory organization includes both one bit per memory cell and multi-level cell capable of storing multiple bits per cell. The memory cells are grouped into words of fixed word length, for example, 1, 2, 4, 8, 16, 32, 64 or 128 bits. Each word can be accessed by a binary address of N bits, making it possible to store 2N words in the memory.
In general, memory is of three types:

1. Primary memory: It is also known as the main memory of the computer system.
2. Secondary memory: It is also known as auxiliary memory and backup memory.
3. Cache memory: It is a type of high-speed semiconductor memory that can help the CPU run faster.

Random Access Memory (RAM)

Introduction

Memory is the most essential element of a computing system because without it computer can’t perform simple tasks. Computer memory is of two basic types – Primary memory(RAM and ROM) and Secondary memory (hard drive, CD, etc). Random Access Memory (RAM) is primary-volatile memory and Read-Only Memory (ROM) is primary-non-volatile memory.
RAM (Random Access Memory) is the hardware in a computing device where the operating system (OS), application programs and data in current use are kept so they can be quickly reached by the device's processor. RAM is the main memory in a computer. It is much faster to read from and write to than other kinds of storage, such as a hard disk drive (HDD), solid-state drive (SSD) or optical drive. Random Access Memory is volatile. That means data is retained in RAM as long as the computer is on, but it is lost when the computer is turned off. When the computer is rebooted, the OS and other files are reloaded into RAM, usually from an HDD or SSD.

Because of its volatility, RAM can't store permanent data. RAM can be compared to a person's short-term memory, and a hard disk drive to a person's long-term memory. Short-term memory is focused on immediate work, but it can only keep a limited number of facts in view at any one time. When a person's short-term memory fills up, it can be refreshed with facts stored in the brain's long-term memory.
A computer also works this way. If RAM fills up, the computer's processor must repeatedly go to the hard disk to overlay the old data in RAM with new data. This process slows the computer's operation.

Types of RAM

• DRAM: Dynamic RAM or DRAM needs to periodically refresh in a few milliseconds to retain data. DRAM is made up of capacitors and transistors and electric charge leaks from capacitors and DRAM needs to be charged periodically. DRAM is widely used in home PCs and servers as it is cheaper than SRAM.
  

  DRAM ​


• SRAM:  Static RAM or SRAM keeps the data as long as power is supplied to the system. SRAM uses Sequential circuits like a flip-flop to store a bit and hence need not be periodically refreshed. SRAM is expensive and hence only used where speed is the utmost priority.
  

  SRAM ​


• SDRAM: Synchronous DRAM, or SDRAM, improves performance through its pins, which sync up with data connection between the main memory and the microprocessor.
  

  SDRAM ​
• DDRSDRAM: DDR SDRAM has the features of SDRAM, but with twice the data transmission frequency. That’s why it’s called “double data rate SDRAM.”
  

  DDRSDRAM ​


• ECC DRAM: This type of DRAM can find corrupted data and sometimes even fix it, thanks to its error-correcting code (ECC).
  

  EECDRAM ​


• DDR2, DDR3, and DDR4: Many HP computers use the DDR series of DRAM chips. The technology improves from one generation to the next, which is indicated by the number series. DDR4, for example, is faster and more efficient than DDR2 or DDR3. If you purchase a new RAM stick to upgrade your computer today, it’s likely that it’ll be a DDR4 chip product. It’s also very easy to install DDR4 RAM in a standard desktop computer, making it popular among hobbyists and pros alike.
  

  DDR ​