Computer Memory

The word "memory" is used to describe an electronic circuit that is able to accommodate the data and program instructions. Memory can be thought of as a work space for computer and memory also determines the size and number of programs that can be run at the same time, as well as the amount of data that can be processed. Memory sometimes referred to as primary storage, primary memory, main storage, main memory, internal storage or also random access memory (RAM). There are four different types of computer memory, namely:

1.      Random Access Memory
2.      Read Only Memory
3.      CMOS Memory
4.      virtual Memory

Random Access Memory (RAM)

When people think of computer memory, it is often random access memory (RAM) is what they mean. RAM consists of a set of chips. These chips were able to accommodate data for processing the instruction or program, to process the data that has been processed and waiting to be sent to output devices, secondary storage or also communication device, instructions operating system controls the basic functions of the computer system. All data and instructions had been accommodated temporarily in RAM. The contents of the RAM can vary according to the data processed therein, or also programs that use it. RAM is the computer resources that are reusable or can be reused.

Most RAM is volatile. It means that if power is disconnected from the computer and the computer tersebu die, then all the content in the RAM will be lost permanently. Because RAM is temporary and volatile, so people create a storage media is permanent. This is usually referred to as secondary storage. Secondary storage is durable and not too volatile, this means all data or programs stored in it can still exist even if the power or the power is turned off. Some examples of this instance is the secondary storage of magnetic tape, hard disk, magnetic disk and optical disk.The storage capacity of the RAM varies in different computers. Capacity is an important factor, since he determines how much data can be processed in the same time and how large and complex programs that can occupy it. The operating system on the computer responsible for managing the use of RAM so that the program can be run properly. To understand the capacity of RAM, then some of the following terminology is often used.Bit, which is a binary numbering system that represents the smallest unit of data in a computer system. A bit only consists of two numbers are 1 and 0. In the computer, a 0 means an electronic or magnetic signal is no or absent, while 1 means the opposite.Byte, which is a group of eight bits. A byte represents one character, one digit or one value. The capacity of the computer memory, or RAM, is expressed in bytes, or a set of bytes.The data, instructions and programs stored in RAM is actually stored in the form of a collection of bits that represent data, instruction and program earlier. These bits are stored in an electronic part called a capacitor microscopic.


Read Only Memory ( ROM )
 
Read Only Memory (ROM) is a set of chips that contain part of the operating system which is needed when the computer is turned on. ROM is also known as a firmware. ROM can not be written or changed its content by users. ROM storage media classified in the non- volatile. Chip ROM comes from the factory with the program or instructions that are already stored on it. The only way to replace its contents is to detach from the computer and replace it with another ROM. ROM chip can contain frequently used programs, such as computing routines to calculate the root of a number, and so forth.  

Read Only Memory (ROM)

  

The use of this example is the ROM as a storage medium of the BIOS (Basic Input-Output System) which diuat by the manufacturer. BIOS is a very critical part of an operating system, which function is to tell the computer how to access the disk drive. When the computer is turned on, RAM is empty and the instructions on the ROM BIOS was used by the CPU to locate the disk drive containing files of the main operating system. The computer then transfer those files into RAM and then run it.There are three variations of ROM, namely:

    PROM, or programmable read only memory. PROM chip is a bare chip which programs can be written into it by using a special equipment. PROM chip can be programmed once and are usually used by plants as a control device in its products.

    EPROM, or erasable programmable read only memory. EPROM similar to a PROM, but the program can be removed and a new program can be written into it by using a special equipment that uses ultraviolet light. EPROM is used for controlling devices such as robots and so on.

    EEPROM, or electronic erasable programmable read only memory. Chip EEPROM can be reprogrammed using a special electric impulses. They do not need to be repealed or amended.

CMOS 

    CMOS stands for "complementary metal oxide semiconductor". CMOS is a special memory that contains vital data about the computer's configuration and are semi-permanent. The absence of this data, the computer will not be able to operate. CMOS is more permanent than the less permanent than the RAM and ROM. CMOS requires very little power to retain its contents, and this chip utilizing the battery as a source of electrical power. When changes are required to the configuration of the computer system (eg no additional hard drive, adding RAM, etc.), then the CMOS can be changed by running a special utility program available through the operating system.

  

VIRTUAL MEMORY

 
Virtual memory is a data storage method in which part of a program or data stored on the magnetic disk and not in RAM, until such time as required. This will give the illusion that the RAM is a kind of unlimited nature. So in conclusion, virtual memory to simulate itself as a RAM. He allows the computer to run more programs than ever before, manipulate the data that is larger and also running large programs without fear of a shortage of RAM. Virtual storage Leih slower than RAM and non-volatile nature.
How can data and programs can be stored in memory
The computer's main memory can be envisioned as a two-dimensional table, where each cell has a unique address. Where each cell can store one byte of data using eight capacitor representing eight bits in a byte.