It provides routines for embedding an interpreter for the S-Lang scripting language, and components to facilitate the creation of text-based applications.

[5] The earliest version of the library contained input/output routines for interacting with computer terminals and an implementation of a simple stack-based interpreter with a PostScript-like syntax that he developed for use in a scientific plotting program.

The JED text editor was the first program to both embed the interpreter and use the terminal I/O components of the library.

As a reflection of Davis's background in physics and professional interest in scientific computing, the language natively supports many vectorized array-based operations similar to MATLAB and IDL.

Version 2.0, released in 2005, made slsh interactive, and it has evolved into an application in its own right, with a number of external modules for use by it.