diff --git a/README.md b/README.md
index fe58e50..fcbb43b 100644
--- a/README.md
+++ b/README.md
@@ -50,6 +50,9 @@ VALUE       OPCODE  EXPLANATION
 
 ### Assembly
 
+- `%25`, decimal
+- `#25`, hex
+
 ```
 2 2 + $ef
 ```
diff --git a/build.sh b/build.sh
index edc664c..378eef4 100755
--- a/build.sh
+++ b/build.sh
@@ -20,4 +20,4 @@ echo "Size: $(du -sk ./uxn)"
 
 # run
 ./uxnasm program.usm program.rom
-# ./uxn program.rom
+./uxn program.rom
diff --git a/program.usm b/program.usm
index 0ad5dda..4af9ba3 100644
--- a/program.usm
+++ b/program.usm
@@ -1 +1 @@
-2 2 + .
\ No newline at end of file
+#12 #34 add 
\ No newline at end of file
diff --git a/uxn.c b/uxn.c
index b788bb3..6c88ec0 100644
--- a/uxn.c
+++ b/uxn.c
@@ -15,6 +15,7 @@ WITH REGARD TO THIS SOFTWARE.
 #define ECHO 1
 
 typedef unsigned char Uint8;
+typedef unsigned char Uint16;
 
 typedef struct {
 
@@ -23,12 +24,13 @@ typedef struct {
 Uint8 sptr;
 Uint8 stack[STACK_DEPTH];
 Uint8 address[STACK_DEPTH];
-Uint8 memory[STACK_DEPTH];
+Uint16 memory[STACK_DEPTH];
 
 void
-stackprint(Uint8 *s, Uint8 len)
+echo(Uint8 *s, Uint8 len, char *name)
 {
 	int i;
+	printf("%s\n", name);
 	for(i = 0; i < len; ++i) {
 		if(i % 16 == 0)
 			printf("\n");
@@ -65,13 +67,12 @@ disk(Computer *cpu, FILE *f)
 	reset(cpu);
 	if(!fread(buffer, sizeof(buffer), 1, f))
 		return 0;
-	/*
-	
+
 	for(i = 0; i < 128; i++) {
 		cpu->memory[i * 2] |= (buffer[i] >> 8) & 0xFF;
 		cpu->memory[i * 2 + 1] |= buffer[i] & 0xFF;
 	}
-	*/
+
 	return 1;
 }
 
@@ -92,12 +93,8 @@ main(int argc, char *argv[])
 	if(!disk(&cpu, f))
 		return error("Unreadable input.");
 	run(&cpu, ECHO);
-	/* program */
-	op_push(stack, 0xef);
-	op_pop(stack);
-	op_push(stack, 0x02);
-	op_push(stack, 0x03);
 	/* print result */
-	stackprint(stack, 0x40);
+	echo(stack, 0x40, "stack");
+	echo(memory, 0x40, "memory");
 	return 0;
 }
diff --git a/uxnasm.c b/uxnasm.c
index c0ca6ff..c3a6b5d 100644
--- a/uxnasm.c
+++ b/uxnasm.c
@@ -11,20 +11,69 @@ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 WITH REGARD TO THIS SOFTWARE.
 */
 
-#define BUFLEN 256
+#define PRGLEN 256
 
 typedef unsigned char Uint8;
-typedef unsigned char Uint16;
+typedef unsigned short Uint16;
 
-unsigned short program[BUFLEN];
+typedef struct {
+	int ptr;
+	Uint16 data[PRGLEN];
+} Program;
+
+Program p;
+
+#pragma mark - Helpers
+
+int
+scmp(char *a, char *b) /* string compare */
+{
+	int i = 0;
+	while(a[i] == b[i])
+		if(!a[i++])
+			return 1;
+	return 0;
+}
+
+int
+shex(char *s) /* string to num */
+{
+	int n = 0, i = 0;
+	char c;
+	while((c = s[i++]))
+		if(c >= '0' && c <= '9')
+			n = n * 16 + (c - '0');
+		else if(c >= 'a' && c <= 'f')
+			n = n * 16 + 10 + (c - 'a');
+	return n;
+}
+
+#pragma mark - Helpers
+
+Uint8
+getopcode(char *s)
+{
+	if(scmp(s, "add")) {
+		return 0x01;
+	}
+	return 0;
+}
 
 void
 pass1(FILE *f)
 {
-	int instrid = 0;
-	char line[BUFLEN];
-	while(fgets(line, BUFLEN, f)) {
-		printf("%s\n", line);
+	char word[64];
+	while(fscanf(f, "%s", word) == 1) {
+		int lit = 0, val = 0;
+		if(word[0] == '#') {
+			lit = 0;
+			val = shex(word + 1);
+		} else {
+			lit = 1;
+			val = getopcode(word);
+		}
+		printf("#%d -> %s[%02x %02x]\n", p.ptr, word, lit, val);
+		p.data[p.ptr++] = (val << 8) + (lit & 0xff);
 	}
 }
 
@@ -44,6 +93,7 @@ main(int argc, char *argv[])
 	if(!(f = fopen(argv[1], "r")))
 		return error("Missing input.");
 	pass1(f);
-	fwrite(program, sizeof(program), 1, fopen(argv[2], "wb"));
+	fwrite(p.data, sizeof(p.data), 1, fopen(argv[2], "wb"));
+	fclose(f);
 	return 0;
 }