Random-access memory

Random-access memory (RAM) is a form of computer data storage. Today, it takes the form of integrated circuits that allow stored data to be accessed in any order with a worst case performance of constant time.

Definition
Strictly speaking, modern types of DRAM are therefore not random access, as data is read in bursts, although the name DRAM / RAM has stuck. However, many types of SRAM, ROM, PROM, and flash memory are still random access even in a strict sense. RAM is often associated with volatile types of memory (such as DRAM memory modules), where its stored information is lost if the power is removed. Many other types of non-volatile memory are RAM as well, including most types of ROM and a type of flash memory called NOR-Flash. The first RAM modules to come into the market were created in 1951 and were sold until the late 1960s and early 1970s.

RAM usage by Apple models
Classic Mac OS left management of memory space up to the user when running more than one application. In 1991, System 7 allowed Macintosh models based around the Motorola 68030 or newer processors the option to enable virtual memory, using hard drive space to supplement physical RAM. Mac OS X, first released in 1999, introduced modern memory management and left virtual memory always on. OS X 10.9 "Mavericks" introduced memory compression of inactive applications.

Base RAM configurations

 * Apple I (1976) — 4KB
 * Macintosh 128K (1984) — 128KB
 * iMac G3 (1997) — 32MB
 * iPhone 1 (2007) — 128MB
 * MacBook Air (2008) — 2GB
 * iPhone X (2017) — 3GB
 * Mac Pro (2019) — 32GB