In the world of computing, main storage is understood to be the program addressable memory that houses the executables and data necessary to launch and run various systems and programs. More commonly referred to as primary storage or memory, main storage directly interfaces with the CPU, which reads the instructions connected with the executables and performs the tasks necessary to handle the data. All data necessary for the effective function of programs saved on the hard drive is maintained in the main storage.
In most cases today, the main storage and the CPU communicate through what is known as the front side bus. This type of bus actually is composed of two specialized buses that help to read both data and addresses that are housed in the main memory. The front side bus extracts the instructions needed to run programs as well as provides the CPU with the location or the address of the executables on the hard drive. The CPU can then read and write the data for itself and proceed to launch the necessary tasks.
It is important to note that in most cases today, main storage is considered to have a volatile memory. This means that the random access memory is cleared at startup. To address this issue, many systems make use of a non-volatile primary main memory or storage component, such as BIOS to effectively bootstrap the computer. Bootstrapping simply means reading a larger program from a secondary storage and loading it to the RAM in primary or main storage. From there, the buses can begin the communication with the CPU and complete the launch sequence.
As part of the ongoing process, the main memory is constantly reading and indexing the data, effectively rewriting it for future use. This constant interaction helps to keep the data refreshed and prevents the data from vanishing from the main storage during the use of various functions and programs that are engaged on the computer system.