andreheringer / khattabmachine

My project for an assembler built to emulate the Khattab Machine.

Khattab Machine

The Khattab Machine is a project propused by Professor Renato Ferreira from my Basic Software class, the goal for the project is to expose students to the entire "software tower" going form the hight level languages (C/C++, Java, Pyhton) to the machine language, going through VM's, assembly, and multiple translations.

The smallest allocable unit by the Khattab Machine(KBM) is a integer, every data processed by the KBM is an integer. The KBM has no less them 1000 memory positions, 3 especial registers and 8 general propose registers.

The tree especial registers are listed as bellow:

• PC (program counter): tells where is the next instruction
• SP (stack pointer): points to the top of the stack
• PEP : Hold the state of the last aritimetic operation, one for zero return operations the other for negative return operations.

Instructions

Code	Symbol	Parameters	Behavior
01	ADD	R1 R2	Reg[R1] ← Reg[R1] + Reg[R2]
02	SUB	R1 R2	Reg[R1] ← Reg[R1]−Reg[R2] *
03	AND	R1 R2	Reg[R1] ← Reg[R1] AND Reg[R2] *
04	OR	R1 R2	Reg[R1] ← Reg[R1] OR Reg[R2] *
05	XOR	R1 R2	Reg[R1] ← Reg[R1] XOR Reg[R2] *
06	NOT	R1	Reg[R1] ←NOT Reg[R1] *
07	JUMP	M	PC ← PC + M
08	JZ	M	PEP[0],PC ← PC + M
09	JNZ	M	!PEP[0],PC ← PC + M
10	JN	M	PEP[negative],PC ← PC + M
11	JNN	M	!PEP[negative],PC ← PC + M
12	PUSH	R	AP ← AP −1 Mem[AP] ← Reg[R]
13	POP	R	Reg[R] ← Mem[AP] & AP ← AP + 1
14	CALL	M	AP ← AP −1 Mem[AP] ← PC & PC ← PC + M
15	LOAD	R M	Reg[R] ← Mem[M + PC]
16	STORE	R M	Mem[M + PC] ← Reg[R]
17	READ	R	Reg[R] ← “Read value”
18	WRITE	R	“Write” Reg[R]
19	COPY	R1 R2	Reg[R1] ← Reg[R2] *
20	RET	None	PC ← Mem[AP] AP ← AP + 1
21	HALT	None	Stop execution

Emulator

READ and WRITE instructions use the emulator's stdin and stdout respectively.

The files recognized by the emulator as executable are the ones using the .mv extention. Check some examples in the tst/ folder.

Assembler

The assembler is implemented in an two-phased parse. First one adding labels to the symbols table, and the second one actually assembling the .mv file for the emulator.

The assembler have two pseudo-instructions:

• WORD A: Save A in the current memory position
• END: Finish the assembler execution

Every line has the format showed bellow and the files expected by the assembler are .amv files, and it outputs .mv files.

[<label>:] <operator> <operand1> <operand2> [; coment]