In this section we are going to learn about types of computer memory.
The devices that are used to store the data and program instructions either temporarily or permanently are called memory and storage devices. Both memory and storage devices are used to store data and instructions but their purpose is different. The purpose of storage devices is to store data permanently even when the computer is switched off. The purpose of memory devices is to store data either temporarily or permanently while the computer works with them. The types of computer memory are broadly classified as:
The primary memory also called as main memory or internal memory of the computer. It is one or more sets of chips that store the data and program instructions, cither temporarily or permanently. It stores data and program instructions during the processing. CPU can quickly read/write data and program instructions from the memory devices. The memory devices are fixed on the motherboard inside the computer case Now-a-days several different types of memories are used in personal computer. The two most important memories are:
- Random Access Memory(RAM)
- Cache Memory
- Read Only Memory (ROM)
- Buffer Memory
Random Access Memory (RAM)
Random Access Memory (RAM) is the temporary or volatile memory. That means the RAM losses its data when the computer is switched off or if there is a power failure. Therefore RAM needs a constant supply of power to hold its data. For this reason we need to save we data files into the storage devices frequently, to avoid losing data in a power failure. We can read data from it and write data into it too. Because of this RAM is also sometimes called read/write memory.
The program and data are stored in RAM during processing so it is called the working memory of the computer. Like other computer components, RAM is made up of a set of chips mounted on a small circuit board. RAM is fixed on the motherboard in the memory card slot. Some of the types of RAM are SRAM and DRAM.
Read Only Memory (ROM)
ROM is the permanent memory of the computer. It permanently stores it’s data even when the computer is switched off. ROM is also called non-volatile memory because it never loses its data. It is read only memory so that we can read data from the ROM but cannot write data into it ROM stores the instructions that the computer needs to operate. When the computer’s power is turned on, it checks ROM for directions that help it start up and for information about its hardware devices. The instructions in the ROM are stored at the time of manufacture of the computer. ROM is fixed on the motherboard inside the computer case. The various types of ROM are PROM, EPROM.
Cache memory is an extremely fast small memory between CPU and Main memory whose access time is closer to the processing speed of CPU. It acts as a high speed buffer memory between CPU and main memory and is used to store very active data and instructions temporarily during processing.
A buffer, also called buffer memory, is a portion of a computer’s memory that is set aside as a temporary holding place for data that is being sent to or received from an external device, such as a hard disk drive (HDD), keyboard or printer.
Secondary memory is where programs and data are kept on a long-term basis. Common secondary storage devices are the hard disk and optical disks. The hard disk has enormous storage capacity compared to main memory. The example of secondary memory are Hard Disk, Folppy Disk, Magnetic tape, Flash disk etc.
The process of using the reserved or additional memory of secondary storage as primary memory is known as virtual memory. Sometimes the primary memory of computer may be insufficient while running large and complex program in such case this memory technique is very much useful.
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