Computers use primary and secondary storage devices. The difference between the storage devices is that the primary storage device houses essential temporary storage devices. The information there is kept for a short time. The secondary storage device keeps the storage of data for much longer periods of time. It is kept until the data is removed or altered externally. The central processor in the computer cannot access the secondary storage directly but it can access the primary storage directly. The information has to be loaded into the primary storage devices in order to do so.
The name for primary storage devices are Random Access Memory (RAM) chips. These RAM chips keep both data and instructions briefly to enable the CPU to perform tasks and keep it running properly. The Random Access Memory comes in two different types: static RAM (SRAM) and dynamic RAM (DRAM). Dynamic Ram (DRAM) keeps information for a short period of time while static ram (SRAM) keeps the data as long as the power to the CPU is not turned off. Both types of RAM keep data temporarily although SRAM keeps it a while longer.
In the past, RAM chips existed as singular chips embedded into the system board. Each of the chips held a byte of memory. This was split up into 9 chips; 8 holding a byte of memory and the 9th holding a parity bit, which kept the computer from crashing by keeping the integrity of the bits in the other 8 chips.
In more current computers, RAM chips became Single Inline Memory Modules, known as SIMMs. A SIMM consists of a singular mini board with 30 or 72 pins on the edge of several chips. A SIMM can hold anywhere from 8MB up to 64MB of Random Access Memory on a single board. It is easier to upgrade RAM since it is located on removable mini boards.
