Function of RAM

Because of its volatility, RAM can’t store permanent data. RAM can be compared to a person’s short-term memory, and a hard disk drive to a person’s long-term memory. Short-term memory is focused on immediate work, but it can only keep a limited number of facts in view at any one time. When a person’s short-term memory fills up, it can be refreshed with facts stored in the brain’s long-term memory.

A computer also works this way. If RAM fills up, the computer’s processor must repeatedly go to the hard disk to overlay the old data in RAM with new data. This process slows the computer’s operation.

Read-only memory (ROM) is a type of storage medium that permanently stores data on personal computers (PCs) and other electronic devices.

It contains the programming needed to start a PC, which is essential for boot-up; it performs major input/output tasks and holds programs or software instructions. This type of memory is often referred to as “firmware”—how it is altered has been a source of design consideration throughout the evolution of the modern computer.

Because ROM is read-only, it cannot be changed; it is permanent and non-volatile, meaning it also holds its memory even when power is removed. By contrast, random access memory (RAM) is volatile; it is lost when power is removed.

The use of the similar term “non-volatile memory” is applicable here (more on that later.) One could say that ROM is, in a sense, “stateful” in its enduring state, where RAM is “stateless.”

In a typical modern computer, there are numerous ROM chips located on the motherboard and a few on expansion boards. The chips are essential for the basic input/output system (BIOS), boot up, reading and writing to peripheral devices, basic data management and the software for basic processes for certain utilities.

ROM may also be referred to as maskROM (MROM). MaskROM is a read-only memory that is static ROM and is programmed into an integrated circuit by the manufacturer. An example of MROM is the bootloader or solid-state ROM, the oldest type of ROM.

The history of read-only memory shows how this type of static memory has worked in engineering over the life cycle of the conventional computer.

Read-only memory was pioneered by machines like Mauchly and Eckert’s Electronic Numerical Integrator and Computer or ENIAC in 1948, and then incarnated in integrated circuits in the 1960s. In earlier personal computers, tools like BASIC interpreters were used to implement read-only memory. The use of BIOS ROM in IBM compatible computers (mentioned above) also became common.