diff --git a/.gitignore b/.gitignore
index fb596ee..37d3d43 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 *.o
 first
+test.rom
diff --git a/Makefile b/Makefile
index 2a6a072..6ee73f9 100644
--- a/Makefile
+++ b/Makefile
@@ -7,16 +7,23 @@ OBJECT_FILES=gui.o main.o simdata.o assembly.o
 ifeq "${QUIET}" "1"
        QUIET_CC     = @echo   ' CC    '$@;
        QUIET_LINK   = @echo   ' LINK  '$@;
+       QUIET_FAS    = @echo   ' FAS   '$@;
        QUIET_CLEAN  = @echo   ' CLEAN .';
        Q            = @
 else
        Q            =
 endif
 
+all:test.rom
+
 first: ${OBJECT_FILES}
 	${QUIET_LINK}
 	${Q}gcc -ggdb $^ -fsanitize=address -lncurses -ltinfo -o $@
 
+%.rom:%.asm first
+	$(QUIET_FAS)
+	${Q}./first -i test.asm -a test.rom
+
 %.o:%.c
 	${QUIET_CC}
 	${Q} gcc -ggdb -c $< -Wall -Wextra -Werror -fsanitize=address
diff --git a/assembly.c b/assembly.c
index 982f39f..bcdf244 100644
--- a/assembly.c
+++ b/assembly.c
@@ -13,6 +13,10 @@
 // +===================================================+
 //
 //
+// Exception:
+//      The bytecode 0xFFFFFFFx is an invalid command
+//    where x is any nibble
+//
 //
 // INSTRUCTION FORMAT 0:
 // +===================================================+
@@ -110,11 +114,11 @@ char *disassemble(uint32_t opcode_be){
 				break;
 			case 0x02:
 			case 0x03:
-				snprintf(ret,MAX_INSTRUCTION_LENGTH,"JMP %s,$%06X",opcode_num&1?"Z":"NZ",val);
+				snprintf(ret,MAX_INSTRUCTION_LENGTH,"JMP,%s $%06X",opcode_num&1?"NZ":"Z",val);
 				break;
 			case 0x04:
 			case 0x05:
-				snprintf(ret,MAX_INSTRUCTION_LENGTH,"JMP %s,$%06X",opcode_num&1?"C":"NC",val);
+				snprintf(ret,MAX_INSTRUCTION_LENGTH,"JMP,%s $%06X",opcode_num&1?"NC":"C",val);
 				break;
 			default:
 				snprintf(ret,MAX_INSTRUCTION_LENGTH,"UNRECOGNISED INSTR");
@@ -148,7 +152,7 @@ char *disassemble(uint32_t opcode_be){
 		}
 	}else if(instruction_format==2){
 		// 16bit opcode
-		opcode_num=(opcode&0x1FFF0000)>>16;
+		opcode_num=(opcode&0x1F000000)>>24;
 		val1=(opcode&0x00FF0000)>>16;
 		val=opcode&0x0000FFFF;
 
@@ -168,3 +172,150 @@ char *disassemble(uint32_t opcode_be){
 
 	return ret;
 }
+
+
+uint32_t assemble_line(char *line, __attribute__((unused)) struct assembler_context_t *assembler_context){
+	uint16_t opcode;
+	int x;
+	if(strncmp(line,"JMP",3)==0){
+		x=3;
+		if(line[x]==' '){
+			opcode=0x01;
+		}else if(line[x]==','){
+			x++;
+			if(line[x]=='Z'){
+				opcode=0x02;
+				x++;
+			}else if(line[x]=='C'){
+				opcode=0x04;
+				x++;
+			}else if(line[x]=='N'){
+				x++;
+				if(line[x]=='Z'){
+					opcode=0x03;
+					x++;
+				}else if(line[x]=='C'){
+					opcode=0x05;
+					x++;
+				}else
+					return 0xFFFFFFFF;
+			}else
+				return 0xFFFFFFFF;
+		}else
+			return 0xFFFFFFFF;
+		while(line[x]==' ')x++;
+		uint32_t addr;
+		if(line[x]=='$'){
+			x++;
+			if(sscanf(line+x,"%06X",&addr)!=1)
+				return 0xFFFFFFFF;
+			else
+				return opcode<<24|(addr&0x00FFFFFF);
+		}else
+			return 0xFFFFFFFF;
+	}else{
+		uint8_t r1,r0,params;
+		if(strncmp(line,"ADD",3)==0){
+			x=3;
+			opcode=0x2000;
+			params=2;
+		}else if(strncmp(line,"SUB",3)==0){
+			x=3;
+			opcode=0x2001;
+			params=2;
+		}else if(strncmp(line,"SL",2)==0){
+			x=2;
+			opcode=0x2002;
+			params=1;
+		}else if(strncmp(line,"SR",2)==0){
+			x=2;
+			opcode=0x2003;
+			params=1;
+		}else if(strncmp(line,"CMP",3)==0){
+			x=3;
+			opcode=0x2004;
+			params=2;
+		}else
+			params=0;
+		if(params!=0){
+			while(line[x]==' ')x++;
+			if(line[x]=='%'){
+				x++;
+				if(line[x]=='R'){
+					x++;
+					if(line[x]>='0'&&line[x]<='7'){
+						r0=line[x]-'0';
+						if(params==2){
+							x++;
+							while(line[x]==' ')x++;
+							if(line[x]==','){
+								x++;
+								while(line[x]==' ')x++;
+								if(line[x]=='%'){
+									x++;
+									if(line[x]=='R'){
+										x++;
+										if(line[x]>='0'&&line[x]<='7'){
+											r1=line[x]-'0';
+											return (opcode<<16)|r0<<8|r1;
+										}else
+											return 0xFFFFFFFF;
+									}else
+										return 0xFFFFFFFF;
+								}else
+									return 0xFFFFFFFF;
+							}else
+								return 0xFFFFFFFF;
+						}else
+							return (opcode<<16)|r0<<8;
+					}else
+						return 0xFFFFFFFF;
+				}else
+					return 0xFFFFFFFF;
+			}else
+				return 0xFFFFFFFF;
+		}else if(strncmp(line,"MOV",3)==0){
+			uint32_t data;
+			x=3;
+			while(line[x]==' ')x++;
+			if(line[x]=='$'){
+				x++;
+				if(sscanf(line+x,"%04X",&data)==1){
+					x+=4;
+					while(line[x]==' ')x++;
+					if(line[x]==','){
+						x++;
+						while(line[x]==' ')x++;
+						if(line[x]=='%'){
+							x++;
+							if(line[x]=='R'){
+								x++;
+								if(line[x]>='0'&&line[x]<='7'){
+									r1=line[x]-'0';
+									x++;
+									if(line[x]=='l')
+										return 0x40000000|r1<<16|data;
+									else if(line[x]=='h')
+										return 0x41000000|r1<<16|data;
+									else
+										return 0xFFFFFFFF;
+								}else
+									return 0xFFFFFFFF;
+							}else
+								return 0xFFFFFFFF;
+						}else
+							return 0xFFFFFFFF;
+					}else
+						return 0xFFFFFFFF;
+				}else
+					return 0xFFFFFFFF;
+			}else
+				return 0xFFFFFFFF;
+		}else
+			return 0xFFFFFFFF;
+	}
+}
+
+void free_assembler_context(struct assembler_context_t *tofree){
+	free(tofree);
+}
diff --git a/assembly.h b/assembly.h
index 373cff4..ff02910 100644
--- a/assembly.h
+++ b/assembly.h
@@ -1,3 +1,16 @@
-#include "stdint.h"
+#include <stdint.h>
 
 char* disassemble(uint32_t opcode);
+
+struct label_ll_t{
+	char* name;
+	uint32_t address;
+	struct label_ll_t *next;
+};
+
+struct assembler_context_t{
+	struct label_ll_t label_ll;
+};
+
+uint32_t assemble_line(char *line, __attribute__((unused)) struct assembler_context_t *assembler_context);
+void free_assembler_context(struct assembler_context_t *tofree);
diff --git a/main.c b/main.c
index c182ec0..a912457 100644
--- a/main.c
+++ b/main.c
@@ -23,16 +23,28 @@
 #include "simdata.h"
 #include <unistd.h>
 #include <errno.h>
+#include "assembly.h"
 
 void help(char* progname){
 	printf("Usage: %s  -i <file> \n", progname);
 }
 
+#define ADDR_SIZE 16777216
+
+int dump_rom(char* filename, struct simdata_t *simdata){
+	FILE* outfile=fopen(filename,"w");
+	for(int i=0;i<ADDR_SIZE;i++)
+		fputc(*(simdata->RAM+i),outfile);
+	fclose(outfile);
+	return 0;
+}
+
 int main(int argc, char* argd[] ){
 	/// PARSE COMMAND LINE ///
 	char *infile = NULL;
+	char *assemble = NULL;
 	int opt;
-	while ((opt = getopt(argc, argd, "hi:")) != -1) {
+	while ((opt = getopt(argc, argd, "hi:a:")) != -1) {
 		switch (opt) {
 			case 'h':
 				help(argd[0]);
@@ -41,6 +53,9 @@ int main(int argc, char* argd[] ){
 			case 'i':
 				infile=optarg;
 				break;
+			case 'a':
+				assemble=optarg;
+				break;
 			default:
 				help(argd[0]);
 				return 1;
@@ -52,57 +67,103 @@ int main(int argc, char* argd[] ){
 		return 1;
 	}
 
-	/// READ ROM FILE ///
+	/// READ INPUT FILE ///
 	FILE* rom=fopen(infile,"r");
 
-	if (rom == NULL) {
-		printf("ERROR: Couldn't open rom file\n");
-		perror(infile);
-		return 1;
-	}
-
-	fseek(rom, 0, SEEK_END);
-	if(ftell(rom)!=16777216){
-		printf("ERROR: ROM file isn't 16MiB\n");
-		return 1;
-	}
-	fseek(rom, 0, SEEK_SET);
-
 	struct simdata_t *simdata = init_simdata();
-	if(!simdata){
-		gui_error("failed to initialise simdata");
-		return 1;
-	}
-	if(fread(simdata->RAM, 16777216, 1, rom)==0){
-		printf("ERROR: failed to read input file\n");
+
+	if ( assemble != NULL ){
+		/* RUN ASSEMBLER */
+		struct assembler_context_t *assembler_context=malloc(sizeof(struct assembler_context_t));
+
+		for (int i=0;i<ADDR_SIZE;i++)
+			simdata->RAM[i]=0;
+		int linec=0;
+		if (rom != NULL) {
+			char line [1000];
+			uint32_t opcode;
+			uint32_t addr=0;
+			while(fgets(line,sizeof(line),rom)!= NULL){
+				opcode=assemble_line(line,assembler_context);
+				if(opcode>0xFFFFFFF1){
+					printf("Error assembling %s:%d\n", infile,linec+1);
+					fclose(rom);
+					free_assembler_context(assembler_context);
+					free_simdata(simdata);
+					return 1;
+				}else{
+					simdata->RAM[addr]=(0xFF000000&opcode)>>24;
+					addr++;
+					simdata->RAM[addr]=(0xFF0000&opcode)>>16;
+					addr++;
+					simdata->RAM[addr]=(0xFF00&opcode)>>8;
+					addr++;
+					simdata->RAM[addr]=(0xFF&opcode);
+					addr++;
+				}
+				linec++;
+			}
+		}
+		free_assembler_context(assembler_context);
+		dump_rom(assemble,simdata);
 		free_simdata(simdata);
-		return 1;
-	}
-	fclose(rom);
+	}else{
+		/* RUN SIMULATOR */
+		if (rom == NULL) {
+			printf("ERROR: Couldn't open rom file\n");
+			perror(infile);
+			fclose(rom);
+			free_simdata(simdata);
+			return 1;
+		}
+
+		fseek(rom, 0, SEEK_END);
+		if(ftell(rom)!=ADDR_SIZE){
+			printf("ERROR: ROM file isn't 16MiB\n");
+			fclose(rom);
+			free_simdata(simdata);
+			return 1;
+		}
+		fseek(rom, 0, SEEK_SET);
+
+		if(!simdata){
+			gui_error("failed to initialise simdata");
+			fclose(rom);
+			free_simdata(simdata);
+			return 1;
+		}
+		if(fread(simdata->RAM, ADDR_SIZE, 1, rom)==0){
+			printf("ERROR: failed to read input file\n");
+			free_simdata(simdata);
+			fclose(rom);
+			return 1;
+		}
+		fclose(rom);
 
 
-	/// INITIALISE GUI ///
-	if(start_gui()){
-		printf("Failed on start_gui()\n");
+		/// INITIALISE GUI ///
+		if(start_gui()){
+			printf("Failed on start_gui()\n");
+			free_simdata(simdata);
+			return 1;
+		}
+
+		update_gui(simdata);
+
+		if(gui_continue_request()){
+			end_gui();
+			printf("Failed on gui_continue_request()\n");
+			free_simdata(simdata);
+			return 1;
+		}
+
+		if(end_gui()){
+			printf("Failed on end_gui()\n");
+			free_simdata(simdata);
+			return 1;
+		}
+
 		free_simdata(simdata);
-		return 1;
 	}
-
-	update_gui(simdata);
-
-	if(gui_continue_request()){
-		end_gui();
-		printf("Failed on gui_continue_request()\n");
-		free_simdata(simdata);
-		return 1;
-	}
-
-	if(end_gui()){
-		printf("Failed on end_gui()\n");
-		free_simdata(simdata);
-		return 1;
-	}
-
-	free_simdata(simdata);
 	return 0;
 }
diff --git a/test.asm b/test.asm
new file mode 100644
index 0000000..b7a8abd
--- /dev/null
+++ b/test.asm
@@ -0,0 +1,7 @@
+JMP $ABCDEF
+JMP,NZ $DEADBA
+JMP,C $EEEEEF
+SL %R7
+CMP %R2,%R0
+MOV $1238,%R5h
+MOV $8321,%R2l