Types of Computer Memory and their Management

In computing memory refer to a device which is used to store a information for immediate used in a computer.
A computer memory is divided into two broad categories which is known as
primary memory
secondary memory

Primary memory:- 

                            primary memory is a internal memory of a computer. It contained on a computer chips and used a electronic circuits to store information. In primary memory, data is not stored permanently, the data is lost when the computer is turn off. The access speed of a internal memory is very high as compared to secondary memory because it accessed directly by the central processing unit.
There are different type of a primary memory are
Read Only Memory (ROM)
Flash Memory
Random Access Memory (RAM)

Read Only Memory:-

                          In Read Only Memory instructions are stored permanently, the store data is not removed when the computer is turn off. Read Only Memory is a Non-volatile Memory. ROM contain a instructions that is very important for computer to start up (boots up). The instructions are read before software program load in the computer from a small program in the ROM. The small program or small part of a ROM is called a "BIOS". Read Only Memory is not re writable it allow only reading. Read Only Memory contain data when computer is switched off.

Flash Memory:-

                       Flash Memory is a solid, Non-volatile and re writable memory. The Flash Memory is used in digital camera's, cell phones, printers,Audio recorders and hand held computers because the speed of Flash Memory is high and the Flash Memory used a low voltage.

Random Access  Memory:-

                                        Random Access Memory is a storage device that can be accessed randomly at any time in any order and from any location. Random Access Memory is a volatile memory. what is volatile memory????
In volatile memory the stored data is lost when computer is off and data remain in memory when machine or computer is running.
Random Access Memory is a readable and re writable memory. We can read data from memory at any time and we can delete the data at any time and again we write data in the memory.
There are two types of Random Access Memory
Static Random Access Memory
Dynamic Access Memory

Static Random Access Memory:-

                                                   Static RAM is a volatile memory it never needs to be refreshed the stored information as power is applied. The content of memory is lost when power is turn off.

Dynamic Random Access Memory:-

                                                         Dynamic RAM is a volatile memory it needs to refreshed the stored information periodically otherwise stored information would be vanish.

Secondary Memory:-

                                 secondary memory is slower than primary memory. Secondary memory is not directly connected to the computer. It hold data after the computer is turn off. Secondary memory has a large capacity to store information but the Access speed of memory is slow. Secondary memory use a inexpensive mass-storage device so secondary memory is inexpensive.
Types of Secondary Memories are
Magnetic Storage Media
Optical Storage Device
Magnetic Storage Device:-

Management of computer memory:-

               The management of computer memory is very important to operate correctly otherwise it leads to bugs, slow performance and virus in the computer.
Arithmetic overflow, segmentation fault, memory leak are all problem of improper management of memory.
Virtual memory and Protected Memory is used to properly manage the computer memory.

Virtual Memory:-

                          When a program needs a memory it request to operating system then operating system decide the location of physical memory to place the memory.
The benefit of virtual memory is where the memory is stored physically without the worry of computer space.

Protected Memory:-

                              In protected memory particular range of memory is allocated to each program to run properly. When program tried to used the space of other program then system terminate the program and help to save data to used incorrectly. protected memory is used to enhanced the reliability and security of the computer system.
       

MAGNETIC TAPE

        Magnetic tape is a nonvolatile just like a disks storage (nonvolatile means that data is not erased from the system when system is turn off). In magnetic tape it is necessary to go through all the data before to reach a specific piece of data that is required. Magnetic tape does not provide a direct access facility for this reason magnetic tape is not suitable for database processing but magnetic tape is mostly used for backup and for storing archival data (the later used data).

For storing a large volume of data the most suitable storage media is magnetic tape, magnetic tape is a cheap and reliable medium for this purpose. The magnetic tape at a very low cost stored a hundred of millions of characters. Some reel holds an 2400 feet of tape and some tape libraries holds a thousand of reels of a tape.

Latest backup tape is used to recreate the database in the case of database disk copy is destroyed. Magnetic tape provides the facility to move data from one place to another place (from one organization to another). The composition of magnetic tape is very simple it is a plastic ribbon with an easily magnetized coating on one side of the disk. The coating material is made of iron oxide or chromium dioxide. The magnetic tape is divided into horizontal and vertical partition. The partition is called a channels (tracks) and frames. Horizontal partition in to a row is called channels or tracks. The vertical partition in to a column is called a frame. The tape drive is needed to load a tape. The tape drive is a device which has a read/write head for each track when tape passes under the heads then entire frame is read automatically. The first few feet at the start for the threading of the tape on the tape drive and last few feet at the end of the tape are left blank.                        

The load point symbol shows the start of the recording on the tape and end-of-reel symbol indicate the last recording on the tape.  Data records on the same tape may be the fixed-length-records or can be the variable-length-records. Inter-record gapes is used to separate the records on the tape. The Inter-records gapes in reality is a blank space between records. The issue of blank spaces is that they slow down the processing of a file because wasting a lot of spaces between many short records. To resolve this issue usually blocks are formed by combining a short record together. These blocks save the spaces that are wasted for separating records from each other on the disks. The numbers of bits per inch of tape determine the data density.