diff --git a/assembly.c b/assembly.c
index 9147790..982f39f 100644
--- a/assembly.c
+++ b/assembly.c
@@ -1,17 +1,170 @@
 #include "assembly.h"
 #include <string.h>
 #include <stdlib.h>
+#include <stdio.h>
 
 
 // Max instruction width is 25 characters without the null char
+//
+// INSTRUCTIONS:
+//    BYTE 3       BYTE 2       BYTE 1       BYTE 0
+// +===================================================+
+// |            |            |            |            |
+// +===================================================+
+//
+//
+//
+// INSTRUCTION FORMAT 0:
+// +===================================================+
+// | OPCODE     |      24 BIT IMMEDIATE ADDRESS        |
+// +===================================================+
+//
+// INSTRUCTION FORMAT 1:
+// +===================================================+
+// |          OPCODE         | SOURCE REG | DEST REG   |
+// +===================================================+
+//
+// INSTRUCTION FORMAT 2:
+// +===================================================+
+// |   OPCODE   | DEST REG   |    16 BIT IMMEDIATE     |
+// +===================================================+
+//
+//
+//
+//  OPCODE FORMAT:
+//  ______________________________________________________________________________________________________
+//  |BIT | 0   | 1   | 2   | 3   | 4   | 5   | 6   | 7   | 8   | 9   | 10  | 11  | 12  | 13  | 14  | 15  |
+//  +----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
+//  |    | INSTR. FORMAT   |    8bit opcode num          :          16bit opcode num                     |
+//  +----+-----------------+-----------------------------+-----------------------------------------------+
+//
+//
+//  INSTRUCTION FORMAT 0 OPCODE NUM:
+//  +-------+----------------------------------+--------------+
+//  | NUM   | DESCRIPTION                      | AFFECT FLAGS |
+//  +-------+----------------------------------+--------------+
+//  | 5'd0  | NOP                              |      NO      |
+//  +-------+----------------------------------+--------------+
+//  | 5'd1  | Unconditional Jump               |      NO      |
+//  +-------+----------------------------------+--------------+
+//  | 5'd2  | Jump if zero flag is set         |      NO      |
+//  +-------+----------------------------------+--------------+
+//  | 5'd3  | Jump if zero flag is not set     |      NO      |
+//  +-------+----------------------------------+--------------+
+//  | 5'd4  | Jump if carry flag is set        |      NO      |
+//  +-------+----------------------------------+--------------+
+//  | 5'd5  | Jump if carry flag is not set    |      NO      |
+//
+//
+//  INSTRUCTION FORMAT 1 OPCODE NUM:
+//  +-------+----------------------------------+--------------+
+//  | NUM   | DESCRIPTION                      | AFFECT FLAGS |
+//  +-------+----------------------------------+--------------+
+//  | 13'd0 | ADD                              |      YES     |
+//  +-------+----------------------------------+--------------|
+//  | 13'd1 | SUBTRACT                         |      YES     |
+//  +-------+----------------------------------+--------------|
+//  | 13'd2 | SHIFT LEFT                       |      YES     |
+//  +-------+----------------------------------+--------------|
+//  | 13'd3 | SHIFT RIGHT                      |      YES     |
+//  +-------+----------------------------------+--------------|
+//  | 13'd4 | COMPARE  (SUBTRACT WITHOUT SAVE) |      YES     |
+//
+//
+//  INSTRUCTION FORMAT 2 OPCODE NUM:
+//  +-------+----------------------------------------------+--------------+
+//  | NUM   | DESCRIPTION                                  | AFFECT FLAGS |
+//  +-------+----------------------------------------------+--------------+
+//  | 5'd0 | MOV IMMEDIATE TO DEST LOW PART OF REGISTER    |      NO      |
+//  +-------+----------------------------------------------+--------------+
+//  | 5'd1 | MOV IMMEDIATE TO DEST HIGH PART OF REGISTER   |      NO      |
+
+#define MAX_INSTRUCTION_LENGTH 26
+
+char *disassemble(uint32_t opcode_be){
+	uint32_t opcode=(opcode_be&0x000000FF)<<24|(opcode_be&0x0000FF00)<<8|(opcode_be&0x00FF0000)>>8|(opcode_be&0xFF000000)>>24;
+	char *ret=malloc(MAX_INSTRUCTION_LENGTH);
 
-char *disassemble(uint32_t opcode){
-	char *ret=malloc(26);
 	if (!ret)
 		return NULL;
-	if(opcode!=0x01ABCDEF)
-		memcpy(ret,"placeholder",12);
-	else
-		memcpy(ret,"easter egg",11);
+
+	//////// PARSE BITECODE //////////
+
+	int instruction_format,opcode_num;
+	uint32_t val;
+	uint8_t val1;
+	uint8_t val2;
+
+	instruction_format=(opcode&0xE0000000)>>29;
+	if(instruction_format==0){
+		// 8bit opcode
+		opcode_num=(opcode&0x1F000000)>>24;
+		val=opcode&0x00FFFFFF;
+
+		switch(opcode_num){
+			case 0x00:
+				snprintf(ret,MAX_INSTRUCTION_LENGTH,"NOP");
+				break;
+			case 0x01:
+				snprintf(ret,MAX_INSTRUCTION_LENGTH,"JMP $%06X",val);
+				break;
+			case 0x02:
+			case 0x03:
+				snprintf(ret,MAX_INSTRUCTION_LENGTH,"JMP %s,$%06X",opcode_num&1?"Z":"NZ",val);
+				break;
+			case 0x04:
+			case 0x05:
+				snprintf(ret,MAX_INSTRUCTION_LENGTH,"JMP %s,$%06X",opcode_num&1?"C":"NC",val);
+				break;
+			default:
+				snprintf(ret,MAX_INSTRUCTION_LENGTH,"UNRECOGNISED INSTR");
+				break;
+		}
+	}else if(instruction_format==1){
+		// 16bit opcode
+		opcode_num=(opcode&0x1FFF0000)>>16;
+		val1=(opcode&0x0000FF00)>>8;
+		val2=opcode&0x000000FF;
+
+		switch(opcode_num){
+			case 0x00:
+				snprintf(ret,MAX_INSTRUCTION_LENGTH,"ADD %%R%0d, %%R%0d",val1,val2);
+				break;
+			case 0x01:
+				snprintf(ret,MAX_INSTRUCTION_LENGTH,"SUB %%R%0d, %%R%0d",val1,val2);
+				break;
+			case 0x02:
+				snprintf(ret,MAX_INSTRUCTION_LENGTH,"SL %%R%0d",val1);
+				break;
+			case 0x03:
+				snprintf(ret,MAX_INSTRUCTION_LENGTH,"SR %%R%0d",val1);
+				break;
+			case 0x04:
+				snprintf(ret,MAX_INSTRUCTION_LENGTH,"CMP %%R%0d, %%R%0d",val1,val2);
+				break;
+			default:
+				snprintf(ret,MAX_INSTRUCTION_LENGTH,"UNRECOGNISED INSTRUCTION");
+				break;
+		}
+	}else if(instruction_format==2){
+		// 16bit opcode
+		opcode_num=(opcode&0x1FFF0000)>>16;
+		val1=(opcode&0x00FF0000)>>16;
+		val=opcode&0x0000FFFF;
+
+		switch(opcode_num){
+			case 0x00:
+				snprintf(ret,MAX_INSTRUCTION_LENGTH,"MOV $%04X, %%R%0dl",val,val1);
+				break;
+			case 0x01:
+				snprintf(ret,MAX_INSTRUCTION_LENGTH,"MOV $%04X, %%R%0dh",val,val1);
+				break;
+			default:
+				snprintf(ret,MAX_INSTRUCTION_LENGTH,"UNRECOGNISED INSTRUCTION");
+				break;
+		}
+	}else
+		snprintf(ret,MAX_INSTRUCTION_LENGTH,"UNRECOGNISED INSTRUCTION");
+
 	return ret;
 }
diff --git a/gui.c b/gui.c
index d621fa0..0b9a95b 100644
--- a/gui.c
+++ b/gui.c
@@ -182,7 +182,7 @@ int update_general_disas(struct simdata_t *simdata){
 	if(width<18){
 		mvwprintw(general_disas,1,1,"too small window");
 	}else{
-		uint32_t ADDRESS=(simdata->PC-(height/2-2)*3)&0x00FFFFFF;
+		uint32_t ADDRESS=(simdata->PC-(height/2-2)*4)&0x00FFFFFF;
 		for (int i=2;i<height-2;i++){
 			int overall_offset=offset_arrow-2;
 
@@ -199,7 +199,7 @@ int update_general_disas(struct simdata_t *simdata){
 			if(ADDRESS==simdata->PC)
 				wattroff(general_disas,A_BOLD);
 
-			ADDRESS=(ADDRESS+3)&0xFFFFFF;
+			ADDRESS=(ADDRESS+4)&0xFFFFFF;
 			free(disas);
 		}
 		mvwaddch(general_disas,height/2,offset_arrow,ACS_RARROW);