Wikipedia
Editors used in the PC environment typically operate in a significantly different manner than those in operation on large Mainframe systems. PC editors are almost universally character stream oriented while mainframe editors are typically text line oriented. Users who need to work on both PCs and mainframes thus need to become productive in two differing work styles.
SPFlite is a free file manager and text editor which provides, on Windows PCs, a familiar working environment for those who are used to IBM's mainframe based ISPF. As well as providing the basic ISPF functional compatibility, SPFLite has added extended facilities to enhance editing abilities.
Originally released in 2004; the current version (as of Mar 26, 2015) is Version 8.2. The program was developed and is maintained by George Deluca and Robert Hodge.
It is one of several PC versions of the mainframe ISPF system, some commercial and some freeware versions. See the links for a list.