What the different between SIEMENS PROGRAM TIA 13 AND TIA 14 AND WHICH ONE YOU preferred ?

Basically, memory. An FB is a function that "remembers", or "keeps score" of its last operations.Both FCs and FBs can hold parameters (IN, OUT, IN-OUT and TEMP), it allows the re-use of the blocks with different calling environments. But FBs have an extra type of parameter: STATIC not available in FCs.When you call an FB, you are required to generate an instance DB (IDB) that accompanies this particular call of an FB; this DB contains all the STATIC parameters of the FB, and these are available at any time by any other block in your program. You could do this with an FC, a general DB and MOVE instructions that would write results of the FC program in that DB. With an FB it is automatic.If you want an example, look at the contents of the System Function Blocks library in Step 7, and look at the grouping of the SFCs and the SFBs. SFCs include SET RTC; this transfers a DT value to the real-time clock of the CPU. Once executed, there is no reason for the function to look back at what it had done. Same thing for SFC20, BLKMOV; once the data has been transfered, no need to remember. But look at the first SFBs: CTU, CTD, TON, TP... Once you have started counting or timing, you might need to look at the value of your accumulated value, or modify the preset. The IDB makes it always available, memorized and accessible, even if the block is not being processed at this exact moment by the CPU. As an exercise call SFB4, TON, in a Lad network; you will be promped for a DB number; put any DBx not presently used to create the IDB. Once the calling block saved, open the blocks folder and see that are the elements of this DB; try modifying them.. The structure od the IDB is linked exclusively to the structure of the FB and is not accessible to you.Now go back to the program, and use any instruction to use the IDB varables in your program. You should be able to use them as any other data in the CPU.Hope this helps,Daniel Chartier

TIA V 14 is latest then TIA V13  having updates libraries and function utilities so proffered TIA V14.