A variant of the language ALGOL, it was developed by Tony Brooker and Derrick Morris for the Atlas computer.
AA high-level routines could include machine code, either to make an inner loop more efficient or to effect some operation which otherwise cannot be done easily.
The complex data type was dropped when Atlas Autocode later evolved into the language Edinburgh IMP.
Atlas Autocode's syntax was largely similar to ALGOL, though it was influenced by the output device which the author had available, a Friden Flexowriter.
[1] Other Flexowriter characters that were found a use in AA were: α in floating-point numbers, e.g., 3.56α-7 for modern 3.56e-7 ; β to mean the second half of a 48-bit Atlas memory word; π for the mathematical constant pi.
When AA was ported to the English Electric KDF9 computer, the character set was changed to International Organization for Standardization (ISO).
[2] Keywords in AA were distinguishable from other text by being underlined, which was implemented via overstrike in the Flexowriter (compare to bold in ALGOL).