Computer memory is not only used to store your movies and music but it is also used to store the instructions and data. It is a storage space that allows the data to process and stores instructions to perform those processes. Memory is further divided into smaller units called cells. Each cell has a unique address which ranges from zero to memory size minus one. The computer works on binary codes to represent the information. Computer storage can be divided into three memory, namely primary, secondary and cache memory.
Let us look at each memory in brief.
Primary memory or main memory –
The main memory stores the instructions and the data that are used currently for processing. It has a limited capacity of storing the data and the data is lost as the system is turned off. It is manufactured by semiconductors and integrated electronic circuits. Primary memory is further divided into two categories:
-Random Access Memory (RAM)-
Random Access Memory (RAM)-
This memory allows the computer to access any specific memory cell without accessing all other cells and thus it is called random access memory. Any part can be accessed randomly for reading or writing the data. RAM’s data can be lost when power supply gets off. This makes it a volatile memory that contains information as long as electric current is available. Dynamic Random Access Memory (DRAM), Synchronous Dynamic Random Access Memory (SDRAM), Static RAM, Video RAM, Flash RAM are the types of RAM.
-Read Only Memory (ROM)
This is a read-only memory and uses the metal oxide semiconductor technology. It is also used to store programs and data frequently used in the system. There are three types of ROM namely Programmable read-only memory (PROM), Erasable programmable read-only memory (EPROM), Electrically erasable programmable read-only memory (EEPROM).
It is also known as the non-volatile memory or external memory. It is used to store the information permanently, but it works slower than the primary memory. This memory is accessed through input and output routines in the system, unlike the primary memory that can be accessed directly. The data of the secondary memory is transferred to the primary memory and then is accessed by the CPU. Moreover, the storage in secondary memory is low because of the low cost per bit. The operating speed of this memory is low as compared to primary memory. Some of the secondary memory are Magnetic Disk, Floppy Disk, Hard Disk and Optical Disks.
It is used for input and output operations at fast access speed. It is used to provide a way to fetch instructions to CPU at the speed of CPU because input and output operations access slowly in the main memory. The CPU searches the cache memory before searching for the main memory. Also, it is located close to CPU that renders it access faster than the other memory.