AIX is short for advanced interactive executive and was first entered into the market by IBM in 1986. AIX is an implementation of Unix derived from both AT&T Unix System V and 4.3 BSD. AIX offers the Korn (ksh) shell, Bourne (sh) and C (csh) shells; however, it defaults to the Korn shell.
AIXL (AIX 5L) is IBM's key element to IBM's AIX / Linux affinity strategy. IBM is working to implement Linux API compatibility within AIX and deliver a common set of application development tools and utilities across AIX and Linux.