diff --git a/instructions.c b/instructions.c
index df37a35..60e0529 100644
--- a/instructions.c
+++ b/instructions.c
@@ -123,8 +123,8 @@ const struct instruction instructions[NR_OPCODES] = {
         OP(SF_CREATEPIXEL, 0), // TODO
         OP(SF_CREATEALPHA, 0), // TODO
 
-        OP(SR_POP, 0), // TODO
-        OP(SR_ASSIGN, 0), // TODO
+        OP(SR_POP, 0),
+        OP(SR_ASSIGN, 0),
         OP(SR_REF, 1, INSTR_INT),
         OP(SR_REFREF, 0), // TODO
         OP(A_ALLOC, 0),
@@ -133,8 +133,8 @@ const struct instruction instructions[NR_OPCODES] = {
         OP(A_NUMOF, 0),
         OP(A_COPY, 0),
         OP(A_FILL, 0),
-        OP(C_REF, 0), // TODO
-        OP(C_ASSIGN, 0), // TODO
+        OP(C_REF, 0),
+        OP(C_ASSIGN, 0),
         OP(MSG, 0), // TODO
         OP(CALLHLL, 0), // TODO
         OP(PUSHSTRUCTPAGE, 0),
diff --git a/string.c b/string.c
index f4af5a4..ca5b949 100644
--- a/string.c
+++ b/string.c
@@ -197,3 +197,49 @@ int string_find(const struct string *haystack, const struct string *needle)
 	}
 	return -1;
 }
+
+int string_get_char(const struct string *str, int i)
+{
+	if ((i = sjis_index(str->text, i)) < 0)
+		ERROR("String index out of bounds");
+
+	if (SJIS_2BYTE(str->text[i]))
+		return (uint8_t)str->text[i] | ((uint8_t)str->text[i+1] << 8);
+	return str->text[i];
+}
+
+void string_set_char(struct string **_str, int i, unsigned int c)
+{
+	struct string *str = *_str = cow_check(*_str);
+	int bytes_src, bytes_dst;
+
+	if ((i = sjis_index(str->text, i)) < 0)
+		ERROR("String index out of bounds");
+
+	bytes_src = SJIS_2BYTE(c) ? 2 : 1;
+	bytes_dst = SJIS_2BYTE(str->text[i]) ? 2 : 1;
+
+	if (bytes_src == 1 && bytes_dst == 1) {
+		str->text[i] = c;
+	} else if (bytes_src == 2 && bytes_dst == 2) {
+		str->text[i]   = c & 0xFF;
+		str->text[i+1] = (c >> 8) & 0xFF;
+	} else if (bytes_src == 1 && bytes_dst == 2) {
+		// shrink 1 byte
+		str->text[i] = c;
+		for (int j = i+1; j < str->size; j++) {
+			str->text[j] = str->text[j+1];
+		}
+		str->size--;
+	} else if (bytes_src == 2 && bytes_dst == 1) {
+		// grow 1 byte
+		str = xrealloc(str, sizeof(struct string) + str->size + 1);
+		str->size++;
+		*_str = str;
+		for (int j = str->size; j > i; j--) {
+			str->text[j] = str->text[j-1];
+		}
+		str->text[i]   = c & 0xFF;
+		str->text[i+1] = (c >> 8) & 0xFF;
+	}
+}
diff --git a/test/Source/strings.jaf b/test/Source/strings.jaf
index 5906875..e7b2419 100755
--- a/test/Source/strings.jaf
+++ b/test/Source/strings.jaf
@@ -67,4 +67,11 @@ void test_strings(void)
 	// FTOS
 	test_bool("(4.2).String()", (f = 4.2, f.String() == "4.200000"), true);
 	test_bool("(4.222).String(2)", (f = 4.222, f.String(2) == "4.22"), true);
+	// C_REF
+	test_equal("abあいう[3]", (s = "abあいう", s[3]), 'い');
+	// C_ASSIGN
+	test_string("abあいう[1] = 'c'", (s = "abあいう", s[1] = 'c', s), "acあいう");
+	test_string("abあいう[3] = 'あ'", (s = "abあいう", s[3] = 'あ', s), "abああう");
+	test_string("abあいう[1] = 'あ'", (s = "abあいう", s[1] = 'あ', s), "aああいう");
+	test_string("abあいう[3] = 'c'", (s = "abあいう", s[3] = 'c', s), "abあcう");
 }
diff --git a/test/Source/structs.jaf b/test/Source/structs.jaf
index 841f485..f11475f 100755
--- a/test/Source/structs.jaf
+++ b/test/Source/structs.jaf
@@ -50,4 +50,10 @@ void test_structs(void)
 	test_equal("nested constructor", c.inner.a, 99);
 	test_equal("nested constructor precedence", c.b, 100);
 	test_equal("c.set_a(22)", (c.set_a(22), c.a), 22);
+
+	my_struct a;
+	my_struct b;
+	a.a = 42;
+	b = a;
+	test_equal("struct assign", b.a, 42);
 }
diff --git a/utfsjis.c b/utfsjis.c
index 50f02e3..93e73d0 100644
--- a/utfsjis.c
+++ b/utfsjis.c
@@ -29,7 +29,7 @@
 #include "utfsjis.h"
 #include "s2utbl.h"
 
-// Convert a byte-index to a character-index for a given SJIS string.
+// Convert a character-index to a byte-index for a given SJIS string.
 int sjis_index(const char *_src, int index)
 {
 	const uint8_t *src = (uint8_t*)_src;
diff --git a/vm.c b/vm.c
index f072d8e..915a643 100644
--- a/vm.c
+++ b/vm.c
@@ -801,12 +801,39 @@ static void execute_instruction(int16_t opcode)
 		v = stack_pop().i; // precision
 		stack_push_string(float_to_string(stack_pop().f, v));
 		break;
+	// --- Characters ---
+	case C_REF:
+		v = stack_pop().i;
+		slot = stack_pop().i;
+		stack_push(string_get_char(heap[slot].s, v));
+		break;
+	case C_ASSIGN:
+		v = stack_pop().i;
+		i = stack_pop().i;
+		slot = stack_pop().i;
+		string_set_char(&heap[slot].s, i, v);
+		stack_push(v);
+		break;
 	//
 	// --- Structs/Classes ---
 	//
 	case SR_REF:
 		stack_push(vm_copy_page(heap[stack_pop_var()->i].page));
 		break;
+	case SR_POP:
+		heap_unref(stack_pop().i);
+		break;
+	case SR_ASSIGN:
+		stack_pop(); // struct type
+		b = stack_pop().i;
+		a = stack_pop().i;
+		if (a == -1)
+			EXECUTION_ERROR("Assignment to null-pointer");
+		if (heap[a].page)
+			delete_page(heap[a].page);
+		heap[a].page = copy_page(heap[b].page);
+		stack_push(b);
+		break;
 	//
 	// -- Arrays --
 	//
diff --git a/vm_string.h b/vm_string.h
index f3b39fb..6a40d82 100644
--- a/vm_string.h
+++ b/vm_string.h
@@ -49,4 +49,8 @@ void string_erase(struct string **s, int index);
 // queries
 int string_find(const struct string *haystack, const struct string *needle);
 
+// characters
+int string_get_char(const struct string *str, int i);
+void string_set_char(struct string **_s, int i, unsigned int c);
+
 #endif