Firstly, if possible I would reconsider the PLC platform you are learning on, the twidosoft platform is 'very old hat' besides the fact that it is virtually obsolete as Telemecanique were aquired by Shneider and subsequently are replacing Telemecaniques PLC with thier own.
But to answer your question (which by the way is very vague to say the least) the 'M' function is an internal flag or memory ie as your example M0.0 represents memory word 0 bit 0, to adress the whole memory word as an integer you would use the prefix MW ie MW10, and to address a floating point you would prefix MF ie MF50, however be wary that the words and bits can overlap, ie if you use M1.14 memory word 1 bit 14 then use and write to MW1, you will over write and action M1.14. This is a very brief look at the "memory function" and can be and is very much more involved than this.
Steve
