A commonly used memory addressing scheme that allows a computer to use hard disk space as substitute for RAM. This technique is often used where a program or programs and the required data cannot be effectively fit into the physical RAM of the computer. A specified area of a hard drive is set aside to act as additional RAM addresses. When a program makes calls to addresses that are not in RAM (but on the drive instead) the computer does a swap whereby some of the data in RAM is written to the drive and then the pertinent data is brought from the drive into RAM. If all goes well the application never knows it is happening, though the user may observe a slight decrease in the speed of the program.