ESA

From GovITwiki

Enterprise Systems Architecture. A 31-bit mainframe architecture introduced by IBM in the 1980s; employed in mainframe hardware such as the ESA/370 and ESA/390; and in operating systems such as Multiple Virtual Storage/ESA (MVS/ESA); Virtual Storage Extended/ESA (VSE/ESA) and Virtual Machine/ESA (VM/ESA). In 2000; IBM introduced a 64-bit successor to ESA called z/Architecture. See MVS; VSE; VM and z/Architecture.