At the time when IS-BASIC was being written, there was a new ANSI Standard being developed for BASIC, and IS-BASIC was based on the latest Standard proposals out at the time. It did not actually become a full Sandard until 1986 - a bit late for the Enterprise!

And a bit late for the rest of the computing world: at the time it looked as though it could become a "big thing", but history shows us that Microsoft BASIC dominated. Despite little use ANSI BASIC also became a European ECMA Standard, an ISO Standard (in 1991) and a Japanese JIS Standard (in 1993).

I have just discovered that it is sometimes also called "Full BASIC". Maybe everyone else knew this, but I did not!   There is a good history of the origins of Full BASIC and how it came about, and the problems in making it an ANSI Standard, on Wikipedia: https://en.wikipedia.org/wiki/Full_BASIC.

I have also come across this interesting article from BYTE magazine, June 1982, "On The Way To Standard BASIC". Written before IS-BASIC was even started, it contains lots of code examples which will look familiar to EP users, and a few hints at things that did not make it into IS-BASIC! http://enterprise.iko.hu/articles/BYTE_1982_06_On_the_Way_to_Standard_BASIC.pdf (thanks Zozosoft for hosting and making it readable)

Do you remember: when the companies bankrupted, there are any plans for the next IS-BASIC version?

I don't remember discussing any further plans. The cost of ROM space was a big issue back then, and new features would mean more ROM space!

We had already gone through a painful process of removing features we had already written in order to save ROM space. I was recently trying to remember what had been removed at this time. One was a PLAY statement as an easy way of producing sound without having to learn about Dave (eg. PLAY "ABCDEFGF#D_" etc. I think you have hit on another with your next question... it has jogged something in my memory!

At the TVC side the version 1 little less than the IS-BASIC, v2 little more, for example: PLOT RECTANGLE, PLOT POLYGON

Again for ROM space reasons, TVC BASIC was a re-write from scratch, except that it "borrowed" some things from IS-BASIC, such as the floating point arithetic routines, and was obviously influenced by it.

After we had done v1, Videoton came up with the money for more ROM space for v2 (I guess EPROMs became cheaper as time moved on... this was now after Enterprise had collapsed, that v2 document is dated May 1987). Now that you have jogged my memory I think some of the "extra" PLOT things in v2 were some of the things removed from the Enterprise to save ROM space!

poking on the EXOS Rom with an Hex editor, that there is some Basic code on it.

As I remember, I also found some BASIC parts in the exos rom. Maybe the default function key definitions. I was surprised that it is the EXOS rom that includes this information, not the BASIC rom.

One was a PLAY statement as an easy way of producing sound without having to learn about Dave (eg. PLAY "ABCDEFGF#D_" etc.

5 years ago I found mentions about deleted statements: https://enterpriseforever.com/hall-of-fame/qa-with-bruce-tanner-is-basic-writer/msg67673/#msg67673