Fortress is a discontinued experimental programming language for high-performance computing, created by Sun Microsystems with funding from DARPA's High Productivity Computing Systems project. One of the language designers was Guy L. Steele Jr., whose previous work includes Scheme, Common Lisp, and Java.
The name "Fortress" was intended to connote a secure Fortran, i.e., "a language for high-performance computation that provides abstraction and type safety on par with modern programming language principles". Language features included implicit parallelism, Unicode support and concrete syntax similar to mathematical notation. The language was not designed to be similar to Fortran. Syntactically, it most resembles Scala, Standard ML, and Haskell. Fortress was designed from the outset to have multiple syntactic stylesheets. Source code can be rendered as ASCII text, in Unicode, or as a prettied image. This would allow for support of mathematical symbols and other symbols in the rendered output for easier reading. An emacs-based tool called fortify transforms ASCII-based Fortress source code into LaTeX output.
Fortress was also designed to be both highly parallel and have rich functionality contained within libraries, drawing from Java. For example, the for loop construct was a parallel operation, which would not necessarily iterate in a strictly linear manner, depending on the underlying implementation. However, the for construct was a library function and could be replaced by another version of the programmer's liking rather than being built into the language.
Fortress' designers made its syntax as close as possible to pseudocode and analyzed hundreds of computer science and mathematics papers, courses, books and journals using pseudocode to extract the common usage patterns of the English language and standard mathematical notation when used to represent algorithms in pseudocode. Then they made the compiler trying to maintain a one-to-one correspondence between pseudocode and executable Fortress.