Our partners in MetaQuotes Software always try to improve the quality of their products, just as we do. That is why they have issued the MQL4 major update, which enables trading terminal MT4 to be as functional as MT5. The update will be naturally compatible with former versions. However, there are few differences.
Firstly, a file structure for storing source codes has been graded. It resulted into modification of the root directory. Previously they were stored in Program Files\<terminal_installation_folder>\, but now can be found in Users\<data_folder>\MQL4\.
Secondly, original (without changes) EX4 files will be totally compatible with the update. The environment copy of older MQL4 versions guarantees stable running of older programs.
The update will be issued on 03.02.2014. More extensive information can be found on the developer's official web-page.