Simulator for a basic computer

This is simple simulator for the basic computer described in the book of Morris Mano "Computer System Architecture". Here professor Hyunsoo Yoo maintains a succinct but complete description of this computer, check it if you can't find the book. In special look for the lectures 5 (Basic Computer Organization and Design) and 6 (Programming the Basic Computer) that this simulator uses as foundation.

This basic computer is built from these components:

Component	Bits	Functionality
DR	16	Data Register
AR	12	Address Register
AC	16	Accumulator
IR	16	Instruction Register
PC	12	Program Counter
TR	16	Temporary Register
INPR	8	Input Register
OUTR	8	Output Register
MEMORY	16	Memory 4096 x 16
FGI	1	Input Flag
FGO	1	Output Flag
IEN	1	Interrupt Enabled Status
R	1	Interruption Status
I	1	Decode Bit
S	1	Halt Status
E	1	Carry Bit
SC	3	Sequence Counter

And the table of instructions it supports is:

	Symbol	Hexcode		Description
		I = 0	I = 1
M E M O R Y	AND	0xxx	8xxx	AND memory word to AC
	ADD	1xxx	9xxx	Add memory word to AC
	LDA	2xxx	Axxx	Load AC from memory
	STA	3xxx	Bxxx	Store content of AC into memory
	BUN	4xxx	Cxxx	Branch unconditionally
	BSA	5xxx	Dxxx	Branch and save return address
	ISZ	6xxx	Exxx	Increment and skip if zero
R E G I S T E R	CLA	7800		Clear AC
	CLE	7400		Clear E
	CMA	7200		Complement AC
	CME	7100		Complement E
	CIR	7080		Circulate right AC and E
	CIL	7040		Circulate left AC and E
	INC	7020		Increment AC
	SPA	7010		Skip next instruction if AC is positive
	SNA	7008		Skip next instruction if AC is negative
	SZA	7004		Skip next instruction if AC is zero
	SZE	7002		Skip next instruction if E is zero
	HLT	7001		Halt computer
I/O	INP	F800		Input character to AC
	OUT	F400		Output character from AC
	SKI	F200		Skip on input flag
	SKO	F100		Skip on output flag
	ION	F080		Interrupt on
	IOF	F040		Interrupt off

The assembler is a bit different than the book, it supports labels of any size and uses the character (:) instead of (,) also I added the LBL pseudo instruction that can help in some cases:

ORG	N	Hexadecimal number N is the memory location
		for the instruction or operand listed in the following line
DEC	N	Signed decimal number N to be converted to the binary
HEX	N	Hexadecimal number N to be converted to the binary
LBL	L	Address of label L to be converted to the binary
END		End of symbolic program

There are 3 sample programs to select, or you can enter your own. After your program is ready press the [Assemble] button, if the program is correct you will need to load the binary codes of the program into memory, you can do this pressing the [Load] button. Now you are ready to run the whole program with [Run] or just go cycle by cycle with [Next].

The source is available under the MIT license in:
http://code.google.com/p/basic-computer-simulator/

Have fun!