diff --git a/stix/lib/comp.c b/stix/lib/comp.c
index 2a2be2f..26efaed 100644
--- a/stix/lib/comp.c
+++ b/stix/lib/comp.c
@@ -1868,9 +1868,9 @@ static int compile_method_primitive (stix_t* stix)
 	while (ptr < end && is_digitchar(*ptr)) 
 	{
 		prim_no = prim_no * 10 + (*ptr - '0');
-		if (prim_no > 0xFFFF) /* TODO: replace 0xFFFF by a macro name */
+		if (prim_no > MAX_CODE_PRIMNO)
 		{
-			set_syntax_error (stix, STIX_SYNERR_PRIMITIVENO, &stix->c->tok.loc, &stix->c->tok.name);
+			set_syntax_error (stix, STIX_SYNERR_PRIMNO, &stix->c->tok.loc, &stix->c->tok.name);
 			return -1;
 		}
 
@@ -2030,8 +2030,8 @@ static int compile_block_temporaries (stix_t* stix)
 
 static int compile_block_expression (stix_t* stix)
 {
-	stix_size_t jump_inst_pos;
-	stix_size_t saved_tmpr_count;
+	stix_size_t i, jump_inst_pos;
+	stix_size_t saved_tmpr_count, saved_tmprs_len;
 	stix_size_t block_arg_count;
 	stix_size_t block_code_size;
 	stix_ioloc_t block_loc, colon_loc;
@@ -2047,6 +2047,7 @@ static int compile_block_expression (stix_t* stix)
 	block_loc = stix->c->tok.loc;
 	GET_TOKEN (stix);
 
+	saved_tmprs_len = stix->c->mth.tmprs.len;
 	saved_tmpr_count = stix->c->mth.tmpr_count;
 
 	if (stix->c->tok.type == STIX_IOTOK_COLON) 
@@ -2073,6 +2074,7 @@ static int compile_block_expression (stix_t* stix)
 			}
 
 			if (add_temporary_variable(stix, &stix->c->tok.name) <= -1) return -1;
+			stix->c->mth.tmpr_count++;
 
 			GET_TOKEN (stix);
 		} 
@@ -2090,20 +2092,36 @@ static int compile_block_expression (stix_t* stix)
 	block_arg_count = stix->c->mth.tmpr_count - saved_tmpr_count;
 	if (block_arg_count > MAX_CODE_NBLKARGS)
 	{
+		/* while an integer object is pused to indicate the number of
+		 * block arguments, evaluation which is done by message passing
+		 * limits the number of arguments that can be passed. so the
+		 * check is implemented */
 		set_syntax_error (stix, STIX_SYNERR_BLKARGFLOOD, &colon_loc, STIX_NULL); 
 		return -1;
 	}
 
+printf ("push_context %d\n", (int)block_arg_count);
+printf ("send_block_copy\n");
 	if (emit_byte_instruction(stix, CODE_PUSH_CONTEXT) <= -1 ||
 	    emit_push_smint_literal(stix, block_arg_count) <= -1 ||
 	    emit_byte_instruction(stix, CODE_SEND_BLOCK_COPY) <= -1) return -1;
 
+printf ("jump\n");
 	/* insert dummy instructions before replacing them with a jump instruction */
 	jump_inst_pos = stix->c->mth.code.len;
-	if (emit_byte_instruction(stix, 0) <= -1 ||
+	if (emit_byte_instruction(stix, MAKE_CODE(CMD_EXTEND_DOUBLE, CMD_JUMP)) <= -1 ||
 	    emit_byte_instruction(stix, 0) <= -1 ||
 	    emit_byte_instruction(stix, 0) <= -1) return -1;
 
+/* TODO: fix this part below */
+	for (i = 0; i < block_arg_count; i++)
+	{
+		/* arrange to store the top of the stack to a block argument
+		 * when evaluation of a block begins */
+		if (emit_positional_instruction(stix, CMD_STORE_INTO_TEMPVAR, i) <= -1) return -1;
+	}
+/* TODO: fix this part above */
+
 	if (compile_block_temporaries(stix) <= -1 ||
 	    compile_block_statements(stix) <= -1) return -1;
 
@@ -2113,17 +2131,22 @@ static int compile_block_expression (stix_t* stix)
 		return -1;
 	}
 
-	block_code_size = stix->c->mth.code.len - jump_inst_pos + 3;
+	block_code_size = stix->c->mth.code.len - jump_inst_pos - 3; /* -3 to exclude JUMP code */
 	if (block_code_size > MAX_CODE_BLKCODE)
 	{
-		set_syntax_error (stix, STIX_SYNERR_BLKFLOOD, &colon_loc, STIX_NULL); 
+		set_syntax_error (stix, STIX_SYNERR_BLKFLOOD, &block_loc, STIX_NULL); 
 		return -1;
 	}
 
-/* TODO: use CMD_EXTEND if block_code_size is <= 255 */
-	stix->c->mth.code.ptr[jump_inst_pos] = MAKE_CODE(CMD_EXTEND_DOUBLE, CMD_JUMP);
-	stix->c->mth.code.ptr[jump_inst_pos + 1] = (block_code_size & 0xFF00u) >> 8;
-	stix->c->mth.code.ptr[jump_inst_pos + 2] = (block_code_size & 0x00FFu);
+/* TODO: use CMD_EXTEND if block_code_size is > 127 or < -128 and shift code by 1 after having eliminated 1 byte.
+	stix->c->mth.code.ptr[jump_inst_pos + 1] = (stix_int8_t)block_code_size & 0xFF;*/
+	/* note that the jump offset is a signed number */
+	stix->c->mth.code.ptr[jump_inst_pos + 1] = ((stix_int16_t)block_code_size) >> 8;
+	stix->c->mth.code.ptr[jump_inst_pos + 2] = ((stix_int16_t)block_code_size & 0xFF);
+
+	/* restore the temporary count */
+	stix->c->mth.tmpr_count = saved_tmpr_count;
+	stix->c->mth.tmprs.len = saved_tmprs_len;
 
 	GET_TOKEN (stix);
 
@@ -2578,6 +2601,7 @@ static int compile_method_statement (stix_t* stix)
 		/* handle the return statement */
 		GET_TOKEN (stix);
 		if (compile_method_expression(stix, 0) <= -1) return -1;
+printf ("return_stacktop\n");
 		return emit_byte_instruction (stix, CODE_RETURN_STACKTOP);
 	}
 	else 
@@ -2593,6 +2617,7 @@ static int compile_method_statement (stix_t* stix)
 		n = compile_method_expression(stix, 1);
 		if (n <= -1) return -1;
 
+if (n == 0) printf ("return_stacktop\n");
 		return (n == 0)? emit_byte_instruction (stix, CODE_POP_STACKTOP): 0;
 	}
 }
@@ -2634,6 +2659,7 @@ static int compile_method_statements (stix_t* stix)
 
 	/* arrange to return the receiver if execution reached 
 	 * the end of the method without explicit return */
+printf ("return_receiver\n");
 	return emit_byte_instruction (stix, CODE_RETURN_RECEIVER);
 }
 
diff --git a/stix/lib/exec.c b/stix/lib/exec.c
index adbb180..20b7e06 100644
--- a/stix/lib/exec.c
+++ b/stix/lib/exec.c
@@ -372,6 +372,33 @@ int primitive_new_with_size (stix_t* stix, stix_ooi_t nargs)
 	return 1; /* success */
 }
 
+int primitive_block_context_value (stix_t* stix, stix_ooi_t nargs)
+{
+	stix_ooi_t sp;
+	stix_oop_block_context_t blkctx;
+
+	LOAD_ACTIVE_SP (stix, sp);
+	blkctx = (stix_oop_block_context_t)STACK_GET(stix, sp - nargs);
+	STIX_ASSERT (STIX_CLASSOF(stix, blkctx) == stix->_block_context);
+
+	if (STIX_OOP_TO_SMINT(blkctx->nargs) != nargs) 
+	{
+		/* the number of argument doesn't match */
+printf ("PRIM BlockContext value FAIL - NARGS MISMATCH\n");
+		return 0;
+	}
+
+	sp -= nargs + 1; /* pop arguments and receiver */
+	STORE_ACTIVE_SP (stix, sp);
+
+	blkctx->ip = blkctx->iip;
+	blkctx->sp = STIX_OOP_FROM_SMINT(nargs);
+	blkctx->caller = (stix_oop_t)stix->active_context;
+
+	stix->active_context = (stix_oop_context_t)blkctx;
+	return 1;
+}
+
 typedef int (*primitive_handler_t) (stix_t* stix, stix_ooi_t nargs);
 
 struct primitive_t
@@ -383,9 +410,10 @@ typedef struct primitive_t primitive_t;
 
 static primitive_t primitives[] =
 {
-	{  -1,   primitive_dump             },
-	{   0,   primitive_new              },
-	{   1,   primitive_new_with_size    }
+	{  -1,   primitive_dump                 },
+	{   0,   primitive_new                  },
+	{   1,   primitive_new_with_size        },
+	{  -1,   primitive_block_context_value  }
 };
 
 int stix_execute (stix_t* stix)
@@ -395,7 +423,7 @@ int stix_execute (stix_t* stix)
 	stix_ooi_t ip, sp;
 
 	stix_byte_t bc, cmd;
-	stix_oow_t b1;
+	stix_ooi_t b1;
 
 	STIX_ASSERT (stix->active_context != STIX_NULL);
 	ip = STIX_OOP_TO_SMINT(stix->active_context->ip);
@@ -411,7 +439,11 @@ int stix_execute (stix_t* stix)
  */
 	while (1)
 	{
-		mth = stix->active_context->method;
+/* TODO: improve how to access method??? */
+		if (stix->active_context->unused == stix->_nil)
+			mth = stix->active_context->method;
+		else
+			mth = ((stix_oop_block_context_t)stix->active_context)->home->method;
 		code = mth->code;
 
 printf ("IP => %d ", (int)ip);
@@ -422,9 +454,22 @@ printf ("IP => %d ", (int)ip);
 		if (cmd == CMD_EXTEND)
 		{
 			cmd = bc & 0xF;
-			b1 = code->slot[ip++];
+			if (cmd == CMD_JUMP || cmd == CMD_JUMP_IF_FALSE)
+				b1 = (stix_int8_t)code->slot[ip++];
+			else
+				b1 = code->slot[ip++];
+			ip++;
+		}
+		else if (cmd == CMD_EXTEND_DOUBLE)
+		{
+			cmd = bc & 0xF;
+			b1 = code->slot[ip++];
+
+			if (cmd == CMD_JUMP || cmd == CMD_JUMP_IF_FALSE)
+				b1 = (stix_int16_t)((b1 << 8) | code->slot[ip++]); /* JUMP encodes a signed offset */
+			else
+				b1 = (b1 << 8) | code->slot[ip++];
 		}
-/* TODO: handle CMD_EXTEND_DOUBLE */
 		else
 		{
 			b1 = bc & 0xF;
@@ -463,8 +508,10 @@ printf ("STORE_TEMPVAR %d\n", (int)b1);
 
 		/* -------------------------------------------------------- */
 
+/* TODO: CMD_JUMP_IF_FALSE */
 			case CMD_JUMP:
-				/* TODO: */
+printf ("JUMP %d\n", (int)b1);
+				ip += b1;
 				break;
 
 		/* -------------------------------------------------------- */
@@ -475,7 +522,10 @@ printf ("STORE_TEMPVAR %d\n", (int)b1);
 				/* b1 -> variable index */
 				stix_ooi_t obj_index;
 				stix_oop_oop_t obj;
+
 				obj_index = code->slot[ip++];
+				if (cmd == CMD_EXTEND_DOUBLE) 
+					obj_index = (obj_index << 8) | code->slot[ip++];
 
 				obj = (stix_oop_oop_t)mth->slot[obj_index];
 printf ("PUSH OBJVAR %d %d\n", (int)b1, (int)obj_index);
@@ -490,6 +540,8 @@ printf ("PUSH OBJVAR %d %d\n", (int)b1, (int)obj_index);
 				stix_ooi_t obj_index;
 				stix_oop_oop_t obj;
 				obj_index = code->slot[ip++];
+				if (cmd == CMD_EXTEND_DOUBLE) 
+					obj_index = (obj_index << 8) | code->slot[ip++];
 
 printf ("STORE OBJVAR %d %d\n", (int)b1, (int)obj_index);
 				obj = (stix_oop_oop_t)mth->slot[obj_index];
@@ -503,8 +555,8 @@ printf ("STORE OBJVAR %d %d\n", (int)b1, (int)obj_index);
 			case CMD_SEND_MESSAGE:
 			case CMD_SEND_MESSAGE_TO_SUPER:
 			{
+/* TODO: tail call optimization */
 				/* b1 -> number of arguments 
-TODO: handle double extension 
 				 */
 				stix_ucs_t mthname;
 				stix_oop_t newrcv;
@@ -516,6 +568,8 @@ TODO: handle double extension
 				/* the next byte is the message selector index to the
 				 * literal frame. */
 				selector_index = code->slot[ip++];
+				if (cmd == CMD_EXTEND_DOUBLE) 
+					selector_index = (selector_index << 8) | code->slot[ip++];
 
 				/* get the selector from the literal frame */
 				selector = (stix_oop_char_t)mth->slot[selector_index];
@@ -574,8 +628,10 @@ printf ("RETURN INSTVAR AT PREAMBLE\n");
 						    (primitives[prim_no].nargs < 0 || primitives[prim_no].nargs == b1))
 						{
 							stix_pushtmp (stix, (stix_oop_t*)&newmth);
+							STORE_ACTIVE_IP (stix, ip);
 							STORE_ACTIVE_SP (stix, sp);
 							n = primitives[prim_no].handler (stix, b1);
+							LOAD_ACTIVE_IP (stix, ip);
 							LOAD_ACTIVE_SP (stix, sp);
 							stix_poptmp (stix);
 							if (n <= -1) goto oops;
@@ -624,14 +680,17 @@ printf ("PUSH_CONTEXT\n");
 						break;
 
 					case SUBCMD_PUSH_NEGONE:
+printf ("PUSH_NEGONE\n");
 						STACK_PUSH (stix, STIX_OOP_FROM_SMINT(-1));
 						break;
 
 					case SUBCMD_PUSH_ZERO:
+printf ("PUSH_ZERO\n");
 						STACK_PUSH (stix, STIX_OOP_FROM_SMINT(0));
 						break;
 
 					case SUBCMD_PUSH_ONE:
+printf ("PUSH_SMINT\n");
 						STACK_PUSH (stix, STIX_OOP_FROM_SMINT(1));
 						break;
 				}
@@ -664,6 +723,52 @@ printf ("RETURN_RECEIVER\n");
 					/*case CMD_RETURN_BLOCK_STACKTOP:*/
 						/* TODO: */
 
+
+					case SUBCMD_SEND_BLOCK_COPY:
+					{
+printf ("SEND_BLOCK_COPY\n");
+						stix_ooi_t nargs;
+						stix_oop_t rctx;
+						stix_oop_block_context_t blkctx;
+
+						/* it emulates thisContext blockCopy: nargs */
+						STIX_ASSERT (sp >= 1);
+						STIX_ASSERT (STIX_CLASSOF(stix, stix->active_context->slot[sp]) == stix->_small_integer);
+						nargs = STIX_OOP_TO_SMINT(stix->active_context->slot[sp]);
+						STIX_ASSERT (nargs >= 0);
+
+						STIX_ASSERT (STIX_CLASSOF(stix, stix->active_context->slot[sp - 1]) == stix->_context);
+
+						blkctx = (stix_oop_block_context_t)stix_instantiate (stix, stix->_block_context, STIX_NULL, 255); /* TODO: proper stack size */
+						if (!blkctx) return -1;
+
+						--sp;
+						rctx = stix->active_context->slot[sp];
+
+						/* blkctx->caller is left to nil */
+						blkctx->ip = STIX_OOP_FROM_SMINT(ip + 3); /* skip the following JUMP */
+						blkctx->sp = 0;
+						blkctx->nargs = STIX_OOP_FROM_SMINT(nargs);
+						blkctx->iip = STIX_OOP_FROM_SMINT(ip + 3);
+
+						if (((stix_oop_block_context_t)rctx)->iip == stix->_nil)
+						{
+							/* the receiver context is a method context */
+							STIX_ASSERT (STIX_CLASSOF(stix, rctx) == stix->_context);
+							blkctx->home = stix->active_context;
+						}
+						else
+						{
+							/* block context is active */
+							STIX_ASSERT (STIX_CLASSOF(stix, rctx) == stix->_block_context);
+							blkctx->home = ((stix_oop_block_context_t)rctx)->home;
+						
+						}
+
+						stix->active_context->slot[sp] = (stix_oop_t)blkctx;
+						break;
+					}
+
 					default:
 						stix->errnum = STIX_EINTERN;
 						break;
diff --git a/stix/lib/stix-prv.h b/stix/lib/stix-prv.h
index 3d8ff7c..4f9af65 100644
--- a/stix/lib/stix-prv.h
+++ b/stix/lib/stix-prv.h
@@ -305,7 +305,7 @@ enum stix_synerrnum_t
 	STIX_SYNERR_ARGFLOOD,      /* too many arguments */
 	STIX_SYNERR_BLKARGFLOOD,   /* too many block arguments */
 	STIX_SYNERR_BLKFLOOD,      /* too large block */
-	STIX_SYNERR_PRIMITIVENO    /* wrong primitive number */
+	STIX_SYNERR_PRIMNO    /* wrong primitive number */
 };
 typedef enum stix_synerrnum_t stix_synerrnum_t;
 
@@ -442,10 +442,14 @@ struct stix_compiler_t
 
 
 #define MAKE_CODE(x,y) (((x) << 4) | y)
-#define MAX_CODE_INDEX               0xFFFFu
-#define MAX_CODE_NARGS               0xFFFFu
-#define MAX_CODE_NBLKARGS            0xFFFFu
-#define MAX_CODE_BLKCODE             0xFFFFu
+#define MAX_CODE_INDEX               (0xFFFFu)
+#define MAX_CODE_NARGS               (0xFFFFu)
+#define MAX_CODE_NBLKARGS            (0xFFFFu)
+#define MAX_CODE_PRIMNO              (0xFFFFu)
+
+#define MIN_CODE_JUMP                (-0x8000)
+#define MAX_CODE_JUMP                (0x7FFF)
+#define MAX_CODE_BLKCODE             MAX_CODE_JUMP
 
 enum stix_cmdcode_t
 {
diff --git a/stix/lib/stix.h b/stix/lib/stix.h
index b76a0ec..ab32cfc 100644
--- a/stix/lib/stix.h
+++ b/stix/lib/stix.h
@@ -603,12 +603,12 @@ struct stix_context_t
 {
 	STIX_OBJ_HEADER;
 
-	stix_oop_t        sender;
+	stix_oop_t        sender; /* message sending context - active context before new context activation*/
 	stix_oop_t        ip;     /* instruction pointer */
 	stix_oop_t        sp;     /* stack pointer */
 	stix_oop_method_t method; /* CompiledMethod */
 	stix_oop_t        unused; 
-	stix_oop_t        receiver;
+	stix_oop_t        receiver; /* receiver of the message. For a statement '#xxx do: #yyyy', #xxx is the receiver.*/
 
 	/* variable indexed part */
 	stix_oop_t        slot[1]; /* stack contents */
@@ -632,21 +632,6 @@ struct stix_block_context_t
 	stix_oop_t        slot[1]; /* stack */
 };
 
-#if 0
-#define STIX_PROCESS_NAMED_INSTVARS 4
-typedef struct stix_process_t stix_process_t;
-typedef struct stix_process_t* stix_oop_process_t;
-struct stix_process_t
-{
-	STIX_OBJ_HEADER;
-	stix_oop_context_t context;
-	stix_oop_t         state; /* SmallInteger */
-
-	stix_oop_process_t prev;
-	stix_oop_process_t next;
-};
-#endif
-
 /**
  * The STIX_CLASSOF() macro return the class of an object including a numeric
  * object encoded into a pointer.