SED (Stream EDitor) is a non-interactive editor, written by Lee E. McMahon in 1973 or 1974 for the Unix operating system, but now available for most OS's. Instead of the user moving the cursor on the screen, the user sends the program a script of editing instructions. In this sense, SED works like a filter - deleting, inserting and changing characters, words, and lines of text. This makes it particularly useful in batch files. Its range of activity goes from small, simple changes to very complex ones.