What is Main Memory in a Computer?

By John Landers

The main memory in a computer is called Random Access Memory. It is also known as RAM. This is the part of the computer that stores operating system software, software applications and other information for the central processing unit (CPU) to have fast and direct access when needed to perform tasks. It is called "random access" because the CPU can go directly to any section of main memory, and does not have go about the process in a sequential order. RAM is one of the faster types of memory, and has the capacity to allow data to be read and written. When the computer is shut down, all of the content held in RAM is purged. Main memory is available in two types: Dynamic Random Access Memory (DRAM) and Static Random Access Memory (SRAM).


The central processing unit is one of the most important components in the computer. It is where various tasks are performed and an output is generated. When the microprocessor completes the execution of a set of instructions, and is ready to carry out the next task, it retrieves the information it needs from RAM. Typically, the directions include the address where the information, which needs to be read, is located. The CPU transmits the address to the RAM's controller, which goes through the process of locating the address and reading the data.


Dynamic random access memory (DRAM) is the most common kind of main memory in a computer. It is a prevalent memory source in PCs, as well as workstations. Dynamic random access memory is constantly restoring whatever information is being held in memory. It refreshes the data by sending millions of pulses per second to the memory storage cell.


Static Random Access Memory (SRAM) is the second type of main memory in a computer. It is commonly used as a source of memory in embedded devices. Data held in SRAM does not have to be continually refreshed; information in this main memory remains as a "static image" until it is overwritten or is deleted when the power is switched off. Since SRAM is less dense and more power-efficient when it is not in use; therefore, it is a better choice than DRAM for certain uses like memory caches located in CPUs. Conversely, DRAM's density makes it a better choice for main memory.

Adequate RAM

The CPU is often considered the most important element in the performance of a personal computer. RAM probably comes in a close second. Having an adequate amount of RAM has a direct effect on the speed of the computer. A system that lacks enough main memory to run its applications must rely on the operating system to create additional memory resources from the hard drive by "swapping" data in and out. When the CPU must retrieve data from the disk instead of RAM, it slows down the performance of the computer. Many games, video-editing or graphics programs require a significant amount of memory to function at an optimal level.

System Requirements

Having adequate main memory in a computer starts with meeting the recommended amount of memory for the operating system. Windows Vista Basic requires a minimum of 512MB of RAM; many computer experts suggest at least 1GB. The minimum requirement for Windows Home Premium, Business and Ultimate is 1GB. MAC OS 10.5 has a minimum requirement of 1GB of main memory.