[Info-vax] VMS internals design, was: Re: BASIC and AST routines

[JP DEMONA]

No DEC language is EASY to migrate. 
in 1M lines of VMS COBOL there will be (generally) 120,000 individual instances that need to be remediated either manually or automatically.
just count how many BY DESCRIPTORS there are your code and that doesn't even scratch the surface.
for PASCAL we had to wrote a DEC PASCAL to C++ converter - does a great job - no other option.
for BASIC we wrote a VAX BASIC to C translator.
for FORTRAN we have FORTRAN partner which is a mil spec VMS FORTRAN to ifort translator - yes - fort is very DEC compatible but dropped many of theold VMS "things" - like initialized common blocks - can have multipack on VMS - only 1 on linux.
Even DEC C in large quanties can be a real pain the the ass - &0, &sizeof, fopen extended to use rms extensions.
we have a DEC COBOL to Fujitsu COBOL / MF COBOL translator - and it earns every penny 
Generally - you can assume that every large DEC 3GL application (1M to 2M LOC) will have 100K+ code modifications to even compile on an ANSI 3GL.
C++ is obviously the easiest - but not immune to DEC isms (you can printf a "string" class)
DEC C - depending on age - can quickly become a quagmire - and we wrote a DEC C to ANSI C converter.

/Jon




On Thursday, November 25, 2021 at 4:07:17 PM UTC-6, Arne Vajhøj wrote:
> On 11/25/2021 4:04 PM, Bill Gunshannon wrote: 
> > On 11/25/21 2:20 PM, Arne Vajhøj wrote: 
> >> Those running VMS today are mostly those without an easy way off 
> >> VMS. 
> > 
> > I would really like to know what people could be running on 
> > VMS on an Itanic that would be so difficult to move to a 
> > totally different system.  Any applications are almost 
> > guaranteed to be written in an HLL.  Just what is it that 
> > they are doing on VMS that can not be done on another 
> > system?
> It can be done on another OS. 
> 
> But the cost and risk migrating can be significant. 
> 
> VMS specific language extensions, SYS$ and LIB$ calls, 
> reliance on special features in Rdb or index-sequential 
> files not available in other RDBMS or ISAM, huge amount 
> of DCL scripts, Macro-32 pieces etc.etc.. 
> 
> A thousand easily solvable problems can when combined 
> be a very problematic cost and risk (risk may very 
> well be considered a bigger problem than cost). 
> 
> It obviously depend on how the code is written. Some 
> C or Cobol programs may be pretty easy to migrate. 
> Most Pascal and Basic programs would be a rewrite from 
> scratch to migrate. 
> 
> Arne