Computer Memory is mainly divided into two parts, one of them is known as primary or main memory and the other one is known as secondary memory.
Is part of the main computer system. All the information that CPU use, is stored and accessible from the primary memory. This implies that all the information stored in a primary memory is easily accessible i.e, Readable and writable through CPU.
Primary memory itself is classified into two categories.
These two categories are RAM (random access memory) and ROM (read only memory).
RAM is a type of memory which is readable and writable. CPU can read and write the information to this primary storage area through RAM. RAM is further classified as DRAM (Dynamic random access memory), RDRAM (Rambus DRAM), SDRAM (Synchronous DRAM), DDR SDRAM (Double Data Rate SDRAM), DDR2 SDRAM(Double Data Rate SDRAM) etc.
The other part of primary storage is just readable ( Read Only Memory ). No changes can be brought in that part of primary memory through CPU. Rom is faster than RAM. The inability of re-writing the ROM memory makes it faster.
Here is the picture of ROM that is installed on the motherboard.
Types of computer memory – Other types
The other types of memory in a computer called secondary memory.
is slow and the cheapest form of memory. CPU cannot process this memory directly, to do any processing on this memory, firstly it has to be copied into the primary memory. It stores data permanently as long as it is not being erased from the memory.
Although, I don’t believe it is used any long, but a floppy disk is one of the types of memory. Others examples are the hard disk, CD, DVD, USB drives and memory cards etc.
Hard disk or hard drive can store a large capacity of data. Its range is from 80GB to Terabytes now. The hard drive is actually made of many magnetic plates, and all the data is stored on these plates. It is a much faster form of secondary memory, it can store data in terabytes. Hard drives are one of the important hardware in our desktop/laptop computers. It is responsible for storing all the files including operating system of the computers.
Compact Disk or CD
A CD (Compact Disk) can store up to 750 MB of data. On CD, data is stored in the pattern of tracks. DVD( Digital Versatile Disk) can store about 4.6 GB of data and information. All these drives are readable and writable, which mean that the data stored on it can be removed anytime and new data can be added using combo CD-RW/DVD-ROM.
Blue ray has recently gone popular among movie enthusiasts. It offers the highest Quality of Video playback, and it requires blue ray compatible CD player.
Removable Hard disk / USB
USB and Portable Hard Drive are the most popular and most commonly used secondary memory types for the computer these days. The sole purpose of a removable hard drive is to easily transfer data from one computer to other. If a file is of large size and emailing it or uploading it to a cloud doesn’t interest you, then these drives can come in handy. Larger files can be easily transferred to these drives and can be accessed, edited or deleted.
Besides all that mentioned above, here are few more types to be read.
Virtual memory is an internal computer memory. It is used when the amount of data that has to be stored is much larger than the capacity of RAM. The operating system stores the excessive data on hard drive temporarily and removes it from the disk when there is enough RAM space is available to keep the operations of OS runs smoothly. Virtual memory effects the speed of processing data when it is compared to the RAM.
Cache memory is used between CPU and RAM so that most frequently used data or instructions can be handled and executed. Cache memory is further divided into 3 levels. Level 1 is primary and is close to the processor. It uses most frequently used data. Level 2 is close to processor and motherboard. Level 3 is most advanced and speedy. This is also utilised to help in the execution of frequently used data.
Volatile memory is a computer memory that needs the power to maintain the storage of information on it. Dynamic RAM is a kind of volatile memory because it works as long as CPU is connected with electric power. It is because dynamic RAM needs the power to prevent loss of data. The moment when the power is turned off, all the data stored in this tempory memory is erased automatically.
Non-volatile memory is the type of memory in computer which retains the information even after the loss of electric supply. ROM, flash memory, hard disk, magnetic tapes etc come under this type of memory.