Define Memory Organization In Detail
Memory unit is one of the important part of hardware. Sometimes un-allocated space of hard disk is used as virtual memory also known as page file. This type of memory is a temporary memory and is used actual memory is less and require some additional memory to perform a specific task.
There are two kinds of computer memory :
- Primary Memory : Primary memory is assessable directly by the processing unit. RAM is an example of primary memory. As soon as the computer is switched off the contents of the primary memory is lost.
- Secondary Memory : Secondary memory such as floppy disks, magnetic disk etc is located outside the computer. Primary memory is more expensive than secondary memory. This memory is also called ‘auxiliary memory’.
Types of Primary Memory ( Main Memory ) :
Read Only Memory ( ROM ) :
It is permanent and is not erased when the system is switched off. The ROM can only be read by the CPU but it can’t be changed. ROM is nonvolatile memory.
Following are the types of ROM :
- PROM (Programmable ROM): In this type of ROM, the information is stored by programmers after manufacturing. It also can’t be altered or erased later on.
- EPROM (Erasable Programmable ROM): It is similar to PROM, but its information can be erased later on by ultra violet light and it can be reprogrammed.
- EEPROM (Electrically Erasable Programmable ROM) : It is similar to EPROM, but its information can be erased by using on high voltage current.
- EAPROM (Electrically Alterable Programmable ROM) : As compared to EPROM and EEPROM, the information stored in EAPROM can be altered later.
Random Access Memory (RAM) :
It is called random access memory because it is possible to randomly select and use any location of the memory directly to store and retrieve data. It is frso called read/write memory. RAM is a volatile memory.
Following are the types of RAM :
- SRAM (Static RAM) : The information stored in static RAM need to be refreshed, but it remains stable as long as power supply is provided. SRAM is costlier but has higher speed than DRAM.
- DRAM (Dynamic RAM): The information stored in dynamic RAM has to be refreshed after every few milliseconds, otherwise it is erased. DRAM has higher storage capacity and is cheaper than SRAM.
CMOS (Complementary Metal Oxide Semiconductor) :
CMOS is used to store the system configuration, date, time and other important data. When the computer is switched on, BIOS matches the information of CMOS with peripheral devices and displays error in case of mismatching.