diff --git a/H/ATOMS b/H/ATOMS
index 62391d6c8..0fd9a78ae 100644
--- a/H/ATOMS
+++ b/H/ATOMS
@@ -137,6 +137,7 @@ A	ExecuteInMod		F	"$execute_in_mod"
 A	ExecuteWithin		F	"$execute_within"
 A	ExecuteWoMod		F	"$execute_wo_mod"
 A	Exist			N	"exist"
+A	Exists			N	"exists"
 A	Exit			N	"exit"
 A	ExistenceError		N	"existence_error"
 A	ExoClause		F	"$exo_clause"
diff --git a/H/generated/iatoms.h b/H/generated/iatoms.h
index 120356855..39f45c8a0 100644
--- a/H/generated/iatoms.h
+++ b/H/generated/iatoms.h
@@ -132,6 +132,7 @@
   AtomExecuteWithin = Yap_FullLookupAtom("$execute_within"); TermExecuteWithin = MkAtomTerm(AtomExecuteWithin);
   AtomExecuteWoMod = Yap_FullLookupAtom("$execute_wo_mod"); TermExecuteWoMod = MkAtomTerm(AtomExecuteWoMod);
   AtomExist = Yap_LookupAtom("exist"); TermExist = MkAtomTerm(AtomExist);
+  AtomExists = Yap_LookupAtom("exists"); TermExists = MkAtomTerm(AtomExists);
   AtomExit = Yap_LookupAtom("exit"); TermExit = MkAtomTerm(AtomExit);
   AtomExistenceError = Yap_LookupAtom("existence_error"); TermExistenceError = MkAtomTerm(AtomExistenceError);
   AtomExoClause = Yap_FullLookupAtom("$exo_clause"); TermExoClause = MkAtomTerm(AtomExoClause);
@@ -377,6 +378,7 @@
   AtomSystem = Yap_LookupAtom("system"); TermSystem = MkAtomTerm(AtomSystem);
   AtomSystemError = Yap_LookupAtom("SYSTEM_ERROR_INTERNAL"); TermSystemError = MkAtomTerm(AtomSystemError);
   AtomSystemLibraryDir = Yap_LookupAtom("system_library_directory"); TermSystemLibraryDir = MkAtomTerm(AtomSystemLibraryDir);
+  AtomT = Yap_LookupAtom("t"); TermT = MkAtomTerm(AtomT);
   AtomTerm = Yap_LookupAtom("term"); TermTerm = MkAtomTerm(AtomTerm);
   AtomTermExpansion = Yap_LookupAtom("term_expansion"); TermTermExpansion = MkAtomTerm(AtomTermExpansion);
   AtomTerms = Yap_LookupAtom("terms"); TermTerms = MkAtomTerm(AtomTerms);
@@ -394,6 +396,7 @@
   AtomTrue = Yap_LookupAtom("true"); TermTrue = MkAtomTerm(AtomTrue);
   AtomTty = Yap_LookupAtom("tty"); TermTty = MkAtomTerm(AtomTty);
   AtomTtys = Yap_LookupAtom("ttys"); TermTtys = MkAtomTerm(AtomTtys);
+  AtomTuple = Yap_LookupAtom("tuple"); TermTuple = MkAtomTerm(AtomTuple);
   AtomTxt = Yap_LookupAtom("txt"); TermTxt = MkAtomTerm(AtomTxt);
   AtomTypeError = Yap_LookupAtom("type_error"); TermTypeError = MkAtomTerm(AtomTypeError);
   AtomUndefined = Yap_LookupAtom("undefined"); TermUndefined = MkAtomTerm(AtomUndefined);
diff --git a/H/generated/ratoms.h b/H/generated/ratoms.h
index 21ed856ca..400c1888e 100644
--- a/H/generated/ratoms.h
+++ b/H/generated/ratoms.h
@@ -132,6 +132,7 @@
   AtomExecuteWithin = AtomAdjust(AtomExecuteWithin); TermExecuteWithin = MkAtomTerm(AtomExecuteWithin);
   AtomExecuteWoMod = AtomAdjust(AtomExecuteWoMod); TermExecuteWoMod = MkAtomTerm(AtomExecuteWoMod);
   AtomExist = AtomAdjust(AtomExist); TermExist = MkAtomTerm(AtomExist);
+  AtomExists = AtomAdjust(AtomExists); TermExists = MkAtomTerm(AtomExists);
   AtomExit = AtomAdjust(AtomExit); TermExit = MkAtomTerm(AtomExit);
   AtomExistenceError = AtomAdjust(AtomExistenceError); TermExistenceError = MkAtomTerm(AtomExistenceError);
   AtomExoClause = AtomAdjust(AtomExoClause); TermExoClause = MkAtomTerm(AtomExoClause);
@@ -377,6 +378,7 @@
   AtomSystem = AtomAdjust(AtomSystem); TermSystem = MkAtomTerm(AtomSystem);
   AtomSystemError = AtomAdjust(AtomSystemError); TermSystemError = MkAtomTerm(AtomSystemError);
   AtomSystemLibraryDir = AtomAdjust(AtomSystemLibraryDir); TermSystemLibraryDir = MkAtomTerm(AtomSystemLibraryDir);
+  AtomT = AtomAdjust(AtomT); TermT = MkAtomTerm(AtomT);
   AtomTerm = AtomAdjust(AtomTerm); TermTerm = MkAtomTerm(AtomTerm);
   AtomTermExpansion = AtomAdjust(AtomTermExpansion); TermTermExpansion = MkAtomTerm(AtomTermExpansion);
   AtomTerms = AtomAdjust(AtomTerms); TermTerms = MkAtomTerm(AtomTerms);
@@ -394,6 +396,7 @@
   AtomTrue = AtomAdjust(AtomTrue); TermTrue = MkAtomTerm(AtomTrue);
   AtomTty = AtomAdjust(AtomTty); TermTty = MkAtomTerm(AtomTty);
   AtomTtys = AtomAdjust(AtomTtys); TermTtys = MkAtomTerm(AtomTtys);
+  AtomTuple = AtomAdjust(AtomTuple); TermTuple = MkAtomTerm(AtomTuple);
   AtomTxt = AtomAdjust(AtomTxt); TermTxt = MkAtomTerm(AtomTxt);
   AtomTypeError = AtomAdjust(AtomTypeError); TermTypeError = MkAtomTerm(AtomTypeError);
   AtomUndefined = AtomAdjust(AtomUndefined); TermUndefined = MkAtomTerm(AtomUndefined);
diff --git a/H/generated/tatoms.h b/H/generated/tatoms.h
index ca19f0125..511346bd0 100644
--- a/H/generated/tatoms.h
+++ b/H/generated/tatoms.h
@@ -132,6 +132,7 @@ Atom AtomExecuteInMod; Term TermExecuteInMod;
 Atom AtomExecuteWithin; Term TermExecuteWithin;
 Atom AtomExecuteWoMod; Term TermExecuteWoMod;
 Atom AtomExist; Term TermExist;
+Atom AtomExists; Term TermExists;
 Atom AtomExit; Term TermExit;
 Atom AtomExistenceError; Term TermExistenceError;
 Atom AtomExoClause; Term TermExoClause;
@@ -377,6 +378,7 @@ Atom AtomSyntaxErrorHandler; Term TermSyntaxErrorHandler;
 Atom AtomSystem; Term TermSystem;
 Atom AtomSystemError; Term TermSystemError;
 Atom AtomSystemLibraryDir; Term TermSystemLibraryDir;
+Atom AtomT; Term TermT;
 Atom AtomTerm; Term TermTerm;
 Atom AtomTermExpansion; Term TermTermExpansion;
 Atom AtomTerms; Term TermTerms;
@@ -394,6 +396,7 @@ Atom AtomTrail;
 Atom AtomTrue; Term TermTrue;
 Atom AtomTty; Term TermTty;
 Atom AtomTtys; Term TermTtys;
+Atom AtomTuple; Term TermTuple;
 Atom AtomTxt; Term TermTxt;
 Atom AtomTypeError; Term TermTypeError;
 Atom AtomUndefined; Term TermUndefined;
diff --git a/os/files.c b/os/files.c
index 7ec0ff06a..be7686da4 100644
--- a/os/files.c
+++ b/os/files.c
@@ -374,8 +374,10 @@ static Int access_file(USES_REGS1) {
   {
     int mode;
 
-    if (atmode == AtomExist)
-      mode = 00;
+    if (atmode == AtomExist)        
+      mode = 00;        
+    else if (atmode == AtomExists)        
+      mode = 00;        
     else if (atmode == AtomWrite)
       mode = 02;
     else if (atmode == AtomRead)
@@ -400,8 +402,10 @@ static Int access_file(USES_REGS1) {
   {
     int mode;
 
-    if (atmode == AtomExist)
-      mode = F_OK;
+    if (atmode == AtomExist)    
+      mode = F_OK;    
+    else if (atmode == AtomExists)    
+      mode = F_OK;    
     else if (atmode == AtomWrite)
       mode = W_OK;
     else if (atmode == AtomRead)