Computer RAM is the best known form of memory your computer uses. Every file or application opened is placed in RAM. Any information the computer needs or uses becomes part of a continuous cycle where the CPU requests data from RAM, processes it and then writes new data back to RAM. This can happen millions of times a second. However, this is usually just for temporary file storage, so unless the data is saved somewhere, it is deleted when the files or applications are closed.
A Hard Drive is a form of computer memory that allows you to permanently store data. This is where all of your permanent files and programs are stored. On computers running with Microsoft windows the Hard Drive is often called C-Drive. The size of a Hard Drive is typically measured in gigabytes.
Virtual memory typically comes into place when applications are too large for the RAM to handle. The operating System uses the hard drive to temporarily store information and take it back when needed. This is normally a lot slower than actual RAM and can possibly degrade performance if used to heavily.
Cache Memory is used in-between the CPU and the RAM and holds the most frequently used data or instructions to be processed.
RAM is a location within the computer system which is responsible for stacking away data on a temporary basis, so that it can be promptly accessed by the processor. The information stored in RAM is typically loaded from the computer's hard disk, and includes data related to the operating system and certain applications. When the system is switched off, RAM loses all the stored information. The data remains stored and can be retained only when the system is running.
When the RAM gets full, the computer system is more likely to operate at a slow speed. The data can be retrieved in any random order. Generally, there are two types of RAM; namely Static RAM (SRAM) and Dynamic RAM (DRAM). When many programs are running on the computer simultaneously, the virtual memory allows the computer to search in RAM for memory portions which haven't been utilized lately and copy them onto the hard drive. This action frees up RAM space and enables the system to load different programs.
This type of memory is active, regardless of whether the system is turned on or is switched off. It is a kind of permanent non-volatile storage memory. As the name 'read only' suggests, the contents in it cannot be changed or modified. It is an integrated circuit which is pre-programmed with important data that should necessarily be present for the computer to carry out its normal functionalities.