I discovered a VAX C compiler on bitsavers:
https://ftpmirror.your.org/pub/misc/bitsavers/bits/DEC/vax/vms/RX50
Failed installations can be problematic so i did a rehearsal on simh using an image of the physical disk. I had to clear some space by deleting files in dua0:[development].
$ @sys$update:vmsinstal vaxc022 dua1:
VAX/VMS Software Product Installation Procedure V4.4
It is 28-APR-2026 at 17:46.
Enter a question mark (?) at any time for help.
* Are you satisfied with the backup of your system disk [YES]?
Please mount the first volume of the set on DUA1:.
* Are you ready? y
%MOUNT-I-MOUNTED, VAXC01 mounted on _ANJIN$DUA1:
The following products will be processed:
VAXC V2.2
Beginning installation of VAXC V2.2 at 17:46
%VMSINSTAL-I-RESTORE, Restoring product saveset A...
%BACKUP-I-READYREAD, mount volume 2 on _ANJIN$DUA1: for reading
Enter "YES" when ready:
Simulation stopped, PC: 80008B1F (BRB 80008B1F)
sim> at rq1 v22d2_BL-CS92D-BE.dsk
sim> c
y
%BACKUP-I-READYREAD, mount volume 3 on _ANJIN$DUA1: for reading
Enter "YES" when ready:
Simulation stopped, PC: 80008B1F (BRB 80008B1F)
sim> at rq1 v22d3_BL-CS93D-BE.dsk
sim> c
y
%BACKUP-I-READYREAD, mount volume 4 on _ANJIN$DUA1: for reading
Enter "YES" when ready:
Simulation stopped, PC: 80008B1F (BRB 80008B1F)
sim> at rq1 v22d4_BL-ey93c-BE.dsk
sim> c
y
VAX C V2.2-015 Installation is commencing ...
* Do you want to run the IVP after the installation [YES]?
* Do you want to purge files replaced by this installation [YES]?
* Do you want to extract .H files from the text library [YES]?
VAX C V2.2-015 : copying images and libraries.
VAX C V2.2-015 : extracting .H files.
A summary of the Software Performance Reports (SPRs) for this release
can be found in the file SYS$LIBRARY:VAXCSPR.DAT.
Your VMS system will now be updated to inculde the following new
and modified files:
SYS$SYSTEM:VAXC.EXE [new]
SYS$LIBRARY:VAXCDEF.TLB [new]
SYS$LIBRARY:VAXCSPR.DAT [new]
SYS$MESSAGE:VAXCERR.EXE [new]
SYS$MESSAGE:VAXCVCGERR.EXE [new]
SYS$MESSAGE:VAXCCRXERR.EXE [new]
SYS$HELP:HELPLIB.HLB [modified]
SYS$LIBRARY:DCLTABLES.EXE [modified]
SYS$EXAMPLES:VAXCIVPP.C [new]
SYS$EXAMPLES:VAXCIVPC.C [new]
VAX C V2.2-015 Installation completed successfully.
%VMSINSTAL-I-MOVEFILES, Files will now be moved to their target directories...
VAX C V2.2-015 Installation Verification Procedure commencing ...
****** VAX C Installation Certification Procedure SUCCESSFUL ******
VAX C V2.2-015 Installation Verification Procedure completed successfull
y.
Installation of VAXC V2.2 completed at 17:47
VMSINSTAL procedure done at 17:47
$ cc
_File: fghgf
%CC-F-OPENIN, error opening SYS$SYSROOT:[SYSMGR]FGHGF.C; as input
-RMS-E-FNF, file not found
$ ls dua0:[000000]
%DCL-W-IVVERB, unrecognized command verb - check validity and spelling
\LS\
$ dir dua0:[000000]
Directory DUA0:[000000]
000000.DIR;1 ANJIN.DIR;1 BACKUP.SYS;1 BADBLK.SYS;1
BADLOG.SYS;1 BITMAP.SYS;1 CONTIN.SYS;1 CORIMG.SYS;1
DEVELOPMENT.DIR;1 INDEXF.SYS;1 JEFF.DIR;1 JENNY.DIR;1
LEND_LEASE.DIR;1 NONPRIV.DIR;1 ORMR.DIR;1
OTHER_DEVELOPMENT.DIR;1 PAPERS.DIR;1 QUOTES.DIR;1
REXONA.DIR;1 SALES.DIR;1 SECURE.DIR;1 SECURITY.DIR;1
STKV2.DIR;1 SYS0.;1 SYS0.DIR;1 SYSEXE.DIR;1
SYSMAINT.DIR;1 SYSWORK.DIR;1 TAPE_LIBRARY.DIR;1 TESTS.DIR;1
TRAINING.DIR;1 USER.DIR;1 V5_DEVELOPMENT.DIR;1
VOLSET.SYS;1
Total of 34 files.
$ dir [000000...]*.c
Directory SYS$SYSROOT:[000000.SYSHLP.EXAMPLES]
VAXCIVPC.C;1 VAXCIVPP.C;1
Total of 2 files.
$ set def SYS$SYSROOT:[000000.SYSHLP.EXAMPLES]
$ cc vaxcivpc
$ dir
Directory SYS$SYSROOT:[000000.SYSHLP.EXAMPLES]
VAXCIVPC.C;1 VAXCIVPC.OBJ;1 VAXCIVPP.C;1 XADRIVER.MAR;1
XALINK.MAR;1 XAMESSAGE.MAR;1 XATEST.COM;1 XATEST.FOR;1
Total of 8 files.
$ cc vaxcivppp
%CC-F-OPENIN, error opening SYS$SYSROOT:[000000.SYSHLP.EXAMPLES]VAXCIVPPP.C; as
input
-RMS-E-FNF, file not found
$ cc vaxcivpp
$ dir /size
Directory SYS$SYSROOT:[000000.SYSHLP.EXAMPLES]
VAXCIVPC.C;1 2
VAXCIVPC.OBJ;1 2
VAXCIVPP.C;1 69
VAXCIVPP.OBJ;1 37
XADRIVER.MAR;1 93
XALINK.MAR;1 5
XAMESSAGE.MAR;1 21
XATEST.COM;1 1
XATEST.FOR;1 10
Total of 9 files, 240 blocks.
$I think i can be fairly confident that VAX C V2.2 will install on the physical system.