diff --git a/C/amasm.c b/C/amasm.c
index 1e5126d82..0a909ee86 100755
--- a/C/amasm.c
+++ b/C/amasm.c
@@ -3685,7 +3685,7 @@ do_pass(int pass_no, yamop **entry_codep, int assembling, int *clause_has_blobsp
     case count_retry_op:
       code_p = a_pl(_count_retry, (PredEntry *)(cip->cpc->rnd1), code_p, pass_no);
       break;
-    case fetch_args_for_bccall:
+    case fetch_args_for_bccall_op:
       if (cip->cpc->nextInst->op != bccall_op) {
 	Yap_Error(INTERNAL_COMPILER_ERROR, TermNil, "compiling binary test", (int) cip->cpc->op);
 	save_machine_regs();
diff --git a/C/compiler.c b/C/compiler.c
index 897abbc35..087d0a0dd 100644
--- a/C/compiler.c
+++ b/C/compiler.c
@@ -447,7 +447,7 @@ c_var(Term t, Int argno, unsigned int arity, unsigned int level, compiler_struct
     }
     break;
   case bt1_flag:
-    Yap_emit(fetch_args_for_bccall, t, 0, &cglobs->cint);
+    Yap_emit(fetch_args_for_bccall_op, t, 0, &cglobs->cint);
     break;
   case bt2_flag:
     Yap_emit(bccall_op, t, (CELL)cglobs->current_p0, &cglobs->cint);
@@ -2196,7 +2196,7 @@ usesvar(compiler_vm_op ic)
   case save_pair_op:
   case f_val_op:
   case f_var_op:
-  case fetch_args_for_bccall:
+  case fetch_args_for_bccall_op:
   case bccall_op:
     return TRUE;
   default:
@@ -2963,7 +2963,7 @@ c_layout(compiler_struct *cglobs)
     case unify_s_var_op:
     case unify_s_val_op:
 #endif
-    case fetch_args_for_bccall:
+    case fetch_args_for_bccall_op:
     case bccall_op:
       checktemp(arg, rn, ic, cglobs);
       break;
diff --git a/C/computils.c b/C/computils.c
index 68efd847d..e7316161e 100644
--- a/C/computils.c
+++ b/C/computils.c
@@ -67,7 +67,7 @@ static char SccsId[] = "%W% %G%";
 #endif
 
 #ifdef DEBUG
-static void ShowOp(char *, struct PSEUDO *);
+static void ShowOp(const char *, struct PSEUDO *);
 #endif /* DEBUG */
 
 /*
@@ -446,7 +446,7 @@ write_functor(Functor f)
 }
 
 static void
-ShowOp (char *f, struct PSEUDO *cpc)
+ShowOp (const char *f, struct PSEUDO *cpc)
 {
   char ch;
   Int arg = cpc->rnd1;
@@ -468,6 +468,7 @@ ShowOp (char *f, struct PSEUDO *cpc)
 #endif
 	  case 'a':
 	  case 'n':
+	  case 'S':
 	    Yap_DebugPlWrite ((Term) arg);
 	    break;
 	  case 'b':
@@ -666,143 +667,286 @@ ShowOp (char *f, struct PSEUDO *cpc)
   Yap_DebugErrorPutc ('\n');
 }
 
-static char *opformat[] =
-{
-  "nop",
-  "get_var\t\t%v,%r",
-  "put_var\t\t%v,%r",
-  "get_val\t\t%v,%r",
-  "put_val\t\t%v,%r",
-  "get_atom\t%a,%r",
-  "put_atom\t%a,%r",
-  "get_num\t\t%n,%r",
-  "put_num\t\t%n,%r",
-  "get_float\t\t%w,%r",
-  "put_float\t\t%w,%r",
-  "get_dbterm\t%w,%r",
-  "put_dbterm\t%w,%r",
-  "get_longint\t\t%w,%r",
-  "put_longint\t\t%w,%r",
-  "get_bigint\t\t%l,%r",
-  "put_bigint\t\t%l,%r",
-  "get_list\t%r",
-  "put_list\t%r",
-  "get_struct\t%f,%r",
-  "put_struct\t%f,%r",
-  "put_unsafe\t%v,%r",
-  "unify_var\t%v",
-  "write_var\t%v",
-  "unify_val\t%v",
-  "write_val\t%v",
-  "unify_atom\t%a",
-  "write_atom\t%a",
-  "unify_num\t%n",
-  "write_num\t%n",
-  "unify_float\t%w",
-  "write_float\t%w",
-  "unify_dbterm\t%w",
-  "write_dbterm\t%w",
-  "unify_longint\t%w",
-  "write_longint\t%w",
-  "unify_bigint\t%l",
-  "write_bigint\t%l",
-  "unify_list",
-  "write_list",
-  "unify_struct\t%f",
-  "write_struct\t%f",
-  "write_unsafe\t%v",
-  "unify_local\t%v",
-  "write local\t%v",
-  "unify_last_list",
-  "write_last_list",
-  "unify_last_struct\t%f",
-  "write_last_struct\t%f",
-  "unify_last_var\t%v",
-  "unify_last_val\t%v",
-  "unify_last_local\t%v",
-  "unify_last_atom\t%a",
-  "unify_last_num\t%n",
-  "unify_last_float\t%w", 
-  "unify_last_dbterm\t%w",
-  "unify_last_longint\t%w",
-  "unify_last_bigint\t%l",
-  "ensure_space",
-  "native_code",
-  "function_to_var\t%v,%B",
-  "function_to_val\t%v,%B",
-  "function_to_0\t%B",
-  "align_float",
-  "fail",
-  "cut",
-  "cutexit",
-  "allocate",
-  "deallocate",
-  "try_me_else\t\t%l\t%x",
-  "jump\t\t%l",
-  "jump\t\t%l",
-  "proceed",
-  "call\t\t%p,%d,%z",
-  "execute\t\t%p",
-  "sys\t\t%p",
-  "%l:",
-  "name\t\t%m,%d",
-  "pop\t\t%l",
-  "retry_me_else\t\t%l\t%x",
-  "trust_me_else_fail\t%x",
-  "either_me\t\t%l,%d,%z",
-  "or_else\t\t%l,%z",
-  "or_last",
-  "push_or",
-  "pushpop_or",
-  "pop_or",
-  "save_by\t\t%v",
-  "commit_by\t\t%v",
-  "patch_by\t\t%v",
-  "try\t\t%g\t%x",
-  "retry\t\t%g\t%x",
-  "trust\t\t%g\t%x",
-  "try_in\t\t%g\t%x",
-  "jump_if_var\t\t%g",
-  "jump_if_nonvar\t\t%g",
-  "cache_arg\t%r",
-  "cache_sub_arg\t%d",
-  "user_index",
-  "switch_on_type\t%h\t%h\t%h\t%h",
-  "switch_on_constant\t%i\n%c",
-  "if_constant\t%i\n%c",
-  "switch_on_functor\t%i\n%e",
-  "if_functor\t%i\n%e",
-  "if_not_then\t%i\t%h\t%h\t%h",
-  "index_on_dbref",
-  "index_on_blob",
-  "index_on_long",
-  "check_var\t %r",
-  "save_pair\t%v",
-  "save_appl\t%v",
-  "pvar_bitmap\t%l,%b",
-  "pvar_live_regs\t%l,%b",
-  "fetch_reg1_reg2\t%N,%N",
-  "fetch_constant_reg\t%l,%N",
-  "fetch_reg_constant\t%l,%N",
-  "fetch_integer_reg\t%d,%N",
-  "fetch_reg_integer\t%d,%N",
-  "enter_profiling\t\t%g",
-  "retry_profiled\t\t%g",
-  "count_call_op\t\t%g",
-  "count_retry_op\t\t%g",
-  "restore_temps\t\t%l",
-  "restore_temps_and_skip\t\t%l",
-  "enter_lu",
-  "empty_call\t\t%l,%d",
+static const char *
+getFormat(compiler_vm_op ic) {
+  switch( ic ) {
+  case nop_op:
+    return "nop";
+  case get_var_op:
+    return "get_var\t\t%v,%r";
+  case put_var_op:
+    return  "put_var\t\t%v,%r";
+  case get_val_op:
+    return "get_val\t\t%v,%r";
+  case put_val_op:
+    return "put_val\t\t%v,%r";
+  case get_atom_op:
+    return "get_atom\t%a,%r";
+  case put_atom_op:
+    return "put_atom\t%a,%r";
+  case get_num_op:
+    return "get_num\t\t%n,%r";
+  case put_num_op:
+    return "put_num\t\t%n,%r";
+  case get_float_op:
+    return "get_float\t\t%w,%r";
+  case put_float_op:
+    return "put_float\t\t%w,%r";
+  case get_string_op:
+    return "get_string\t\t%w,%S";
+  case put_string_op:
+    return "put_string\t\t%w,%S";
+  case get_dbterm_op:
+    return "get_dbterm\t%w,%r";
+  case put_dbterm_op:
+    return "put_dbterm\t%w,%r";
+  case get_longint_op:
+    return "get_longint\t\t%w,%r";
+  case put_longint_op:
+    return "put_longint\t\t%w,%r";
+  case get_bigint_op:
+    return "get_bigint\t\t%l,%r";
+  case put_bigint_op:
+    return "put_bigint\t\t%l,%r";
+  case get_list_op:
+    return "get_list\t%r";
+  case put_list_op:
+    return "put_list\t%r";
+  case get_struct_op:
+    return "get_struct\t%f,%r";
+  case put_struct_op:
+    return "put_struct\t%f,%r";
+  case put_unsafe_op:
+    return "put_unsafe\t%v,%r";
+  case unify_var_op:
+    return "unify_var\t%v";
+  case write_var_op:
+    return "write_var\t%v";
+  case unify_val_op:
+    return "unify_val\t%v";
+  case write_val_op:
+    return "write_val\t%v";
+  case unify_atom_op:
+    return "unify_atom\t%a";
+  case write_atom_op:
+    return "write_atom\t%a";
+  case unify_num_op:
+    return "unify_num\t%n";
+  case write_num_op:
+    return "write_num\t%n";
+  case unify_float_op:
+    return "unify_float\t%w";
+  case write_float_op:
+    return "write_float\t%w";
+  case unify_string_op:
+    return "unify_string\t%S";
+  case write_string_op:
+    return "write_string\t%S";
+  case unify_dbterm_op:
+    return "unify_dbterm\t%w";
+  case write_dbterm_op:
+    return "write_dbterm\t%w";
+  case unify_longint_op:
+    return "unify_longint\t%w";
+  case write_longint_op:
+    return "write_longint\t%w";
+  case unify_bigint_op:
+    return "unify_bigint\t%l";
+  case write_bigint_op:
+    return "write_bigint\t%l";
+  case unify_list_op:
+    return "unify_list";
+  case write_list_op:
+    return "write_list";
+  case unify_struct_op:
+    return "unify_struct\t%f";
+  case write_struct_op:
+    return "write_struct\t%f";
+  case write_unsafe_op:
+    return "write_unsafe\t%v";
+  case unify_local_op:
+    return "unify_local\t%v";
+  case write_local_op:
+    return "write local\t%v";
+  case unify_last_list_op:
+    return "unify_last_list";
+  case write_last_list_op:
+    return "write_last_list";
+  case unify_last_struct_op:
+    return "unify_last_struct\t%f";
+  case write_last_struct_op:
+    return "write_last_struct\t%f";
+  case unify_last_var_op:
+    return "unify_last_var\t%v";
+  case unify_last_val_op:
+    return "unify_last_val\t%v";
+  case unify_last_local_op:
+    return "unify_last_local\t%v";
+  case unify_last_atom_op:
+    return "unify_last_atom\t%a";
+  case unify_last_num_op:
+    return "unify_last_num\t%n";
+  case unify_last_float_op:
+     return "unify_last_float\t%w";
+  case unify_last_string_op:
+     return "unify_last_string\t%S";
+  case unify_last_dbterm_op:
+    return "unify_last_dbterm\t%w";
+  case unify_last_longint_op:
+    return "unify_last_longint\t%w";
+  case unify_last_bigint_op:
+    return "unify_last_bigint\t%l";
+  case ensure_space_op:
+    return "ensure_space";
+  case native_op:
+    return "native_code";
+  case f_var_op:
+    return "function_to_var\t%v,%B";
+  case f_val_op:
+    return "function_to_val\t%v,%B";
+  case f_0_op:
+    return "function_to_0\t%B";
+  case align_float_op:
+    return "align_float";
+  case fail_op:
+    return "fail";
+  case cut_op:
+    return "cut";
+  case cutexit_op:
+    return "cutexit";
+  case allocate_op:
+    return "allocate";
+  case deallocate_op:
+    return "deallocate";
+  case tryme_op:
+    return "try_me_else\t\t%l\t%x";
+  case jump_op:
+    return "jump\t\t%l";
+  case jumpi_op:
+    return "jump_in_indexing\t\t%i";
+  case procceed_op:
+    return "proceed";
+  case call_op:
+    return "call\t\t%p,%d,%z";
+  case execute_op:
+    return "execute\t\t%p";
+  case safe_call_op:
+    return "sys\t\t%p";
+  case label_op:
+    return "%l:";
+  case name_op:
+    return "name\t\t%m,%d";
+  case pop_op:
+    return "pop\t\t%l";
+  case retryme_op:
+    return "retry_me_else\t\t%l\t%x";
+  case trustme_op:
+    return "trust_me_else_fail\t%x";
+  case either_op:
+    return "either_me\t\t%l,%d,%z";
+  case orelse_op:
+    return "or_else\t\t%l,%z";
+  case orlast_op:
+    return "or_last";
+  case push_or_op:
+    return "push_or";
+  case pop_or_op:
+    return "pop_or";
+  case pushpop_or_op:
+    return "pushpop_or";
+  case save_b_op:
+    return "save_by\t\t%v";
+  case commit_b_op:
+    return "commit_by\t\t%v";
+  case patch_b_op:
+    return "patch_by\t\t%v";
+  case try_op:
+    return "try\t\t%g\t%x";
+  case retry_op:
+    return "retry\t\t%g\t%x";
+  case trust_op:
+    return "trust\t\t%g\t%x";
+  case try_in_op:
+    return "try_in\t\t%g\t%x";
+  case jump_v_op:
+    return "jump_if_var\t\t%g";
+  case jump_nv_op:
+    return "jump_if_nonvar\t\t%g";
+  case cache_arg_op:
+    return "cache_arg\t%r";
+  case cache_sub_arg_op:
+    return "cache_sub_arg\t%d";
+  case user_switch_op:
+    return "user_switch";
+  case switch_on_type_op:
+    return "switch_on_type\t%h\t%h\t%h\t%h";
+  case switch_c_op:
+    return "switch_on_constant\t%i\n%c";
+  case if_c_op:
+    return "if_constant\t%i\n%c";
+  case switch_f_op:
+    return "switch_on_functor\t%i\n%e";
+  case if_f_op:
+    return "if_functor\t%i\n%e";
+  case if_not_op:
+    return "if_not_then\t%i\t%h\t%h\t%h";
+  case index_dbref_op:
+    return "index_on_dbref";
+  case index_blob_op:
+    return "index_on_blob";
+  case index_long_op:
+    return "index_on_blob";
+  case index_string_op:
+    return "index_on_string";
+  case 	if_nonvar_op:
+    return "check_var\t %r";
+  case save_pair_op:
+    return "save_pair\t%v";
+  case save_appl_op:
+    return "save_appl\t%v";
+  case mark_initialised_pvars_op:
+    return "pvar_bitmap\t%l,%b";
+  case mark_live_regs_op:
+    return "pvar_live_regs\t%l,%b";
+  case fetch_args_vv_op:
+    return "fetch_reg1_reg2\t%N,%N";
+  case fetch_args_cv_op:
+    return "fetch_constant_reg\t%l,%N";
+  case fetch_args_vc_op:
+    return "fetch_reg_constant\t%l,%N";
+  case fetch_args_iv_op:
+    return "fetch_integer_reg\t%d,%N";
+  case fetch_args_vi_op:
+    return "fetch_reg_integer\t%d,%N";
+  case enter_profiling_op:
+    return "enter_profiling\t\t%g";
+  case retry_profiled_op:
+    return "retry_profiled\t\t%g";
+  case count_call_op:
+    return "count_call_op\t\t%g";
+  case count_retry_op:
+    return "count_retry_op\t\t%g";
+  case restore_tmps_op:
+    return "restore_temps\t\t%l";
+  case restore_tmps_and_skip_op:
+    return "restore_temps_and_skip\t\t%l";
+  case enter_lu_op:
+    return "enter_lu";
+  case empty_call_op:
+    return "empty_call\t\t%l,%d";
 #ifdef YAPOR
-  "sync",
+  case sync_op:
+    return "sync";
 #endif /* YAPOR */
 #ifdef TABLING
-  "table_new_answer",
-  "table_try_single\t%g\t%x",
+  case table_new_answer_op:
+    return "table_new_answer";
+  case table_try_single_op:
+    return "table_try_single\t%g\t%x";
 #endif /* TABLING */
 #ifdef TABLING_INNER_CUTS
-  "clause_with_cut",
+  case "clause_with_cut":
+    return clause_with_cut_op;
 #endif /* TABLING_INNER_CUTS */
 #ifdef BEAM
   "run_op %1,%4",
@@ -828,10 +972,16 @@ static char *opformat[] =
   "equal_op",
   "exit",
 #endif
-  "fetch_args_for_bccall\t%v",
-  "binary_cfunc\t\t%v,%P",
-  "blob\t%O",
-  "label_control\t"
+  case fetch_args_for_bccall_op:
+    return "fetch_args_for_bccall\t%v";
+  case bccall_op:
+    return "binary_cfunc\t\t%v,%P";
+  case blob_op:
+    return "blob\t%O";
+  case string_op:
+    return "string\t%O";
+  case label_ctl_op:
+    return "label_control\t";
 #ifdef SFUNC
   ,
   "get_s_f_op\t%f,%r",
@@ -849,14 +999,13 @@ static char *opformat[] =
   "unify_s_end",
   "write_s_end"
 #endif
-};
-
+    }
+}
 
 void
 Yap_ShowCode (struct intermediates *cint)
 {
   CACHE_REGS
-  CELL *oldH = HR;
   struct PSEUDO *cpc;
 
   cpc = cint->CodeStart;
@@ -865,12 +1014,11 @@ Yap_ShowCode (struct intermediates *cint)
   while (cpc) {
     compiler_vm_op ic = cpc->op;
     if (ic != nop_op) {
-      ShowOp (opformat[ic], cpc);
-    }
+      }
+    ShowOp (getFormat(ic), cpc);
     cpc = cpc->nextInst;
   }
   Yap_DebugErrorPutc ('\n');
-  HR = oldH;
 }
 
 #endif /* DEBUG */
diff --git a/H/compile.h b/H/compile.h
index c4a508006..60863826b 100644
--- a/H/compile.h
+++ b/H/compile.h
@@ -185,7 +185,7 @@ typedef enum compiler_op {
   equal_op,
   exit_op, 
 #endif
-  fetch_args_for_bccall,
+  fetch_args_for_bccall_op,
   bccall_op,
   blob_op,
   string_op,