cipher.mli

;   ---------------------------------------------------------------------
;
;              Name: Matthew Ball
;    Student Number: 4537508
;            Course: COMP2300
; Assignment Number: 2
; Name of this file: cipher.mli
;        Lab Group: Thursday, 8:00am - 10:00am
; 
;
; I declare that the material I am submitting in this file is entirely
; my own work.  I have not collaborated with anyone to produce it, nor
; have I copied it, in part or in full, from work produced by someone else.
; I have not given access to this material to any other student in this course.
;   ---------------------------------------------------------------------

START a20		; start address of the program.
   			; initialise PC to this.
AT a0
0000 0000 0000 0000	; a0: memory cell to store nextChar variable		char nextChar;
0000 0000 0000 1101	; a1: memory cell to store ROT field			#define ROT 13
0000 0000 0100 0000	; a2: memory cell to store the value A-1 (64)		#define A 64
0000 0000 0101 1011	; a3: memory cell to store the value Z+1 (91)		#define Z 91
0000 0000 0110 0000	; a4: memory cell to store the value a-1 (96)		#define a 96
0000 0000 0111 1011	; a5: memory cell to store the value z+1 (123)		#define z 123
0000 0000 0101 1010	; a6: memory cell to store the value 90
0000 0000 0111 1010	; a7: memory cell to store the value 122

AT a20			; store the following instructions:
			; main procedure
110101  0000 0000 10	; a20: trap 2 (Get), read character			getchar(); //Start Loop
001 010 a0		; a21: store character in mem[a0] (nextChar)		nextChar = mem[a0];
000 111 0000 0010 10	; a22: compare to EOL character				if (nextChar == EOL)
101001  a36		; a23: if equal branch to mem[a36]				goto(mem[a36]);

			; check for lower case
			; ----------------------
			; check for lower bounds
001 111 a4		; a24: compare AC to mem[a4] (96)			if (nextChar <= mem[a4])
101100  a34		; a25: branch less/equal (if AC <= 96) skip to mem[a34]		goto(mem[a34]);
			; check for upper bounds
001 111 a5		; a26: compare AC to mem[a5] (123)			if (nextChar > mem[a5])
101011  a44		; a27: branch greater (if AC > 123) skip to mem[a44]		goto(mem[a44]);
			; rotate character
001 011 a1		; a30: AC + mem[a1] (13)				nextChar += mem[a1];
001 111 a7		; a31: compare AC to mem[a7] (122)			if (AC <= 122)
101100  a44		; a32: branch less/equal (if AC <= 122) skip to mem[a44]	goto(mem[a44]);
000 100 0000 0110 10	; a33: AC - 26						nextChar -= 26;

			; check for upper case
			; ----------------------
			; check for lower bounds
001 111 a2		; a34: compare AC to mem[a2] (64)			if (nextChar <= mem[a2])
101100  a44		; a35: branch less/equal (if AC <= 64) skip to mem[a44]		goto(mem[a44]);
			; check for upper bounds
001 111 a3		; a36: compare AC to mem[a3] (91)			if (nextChar > mem[a3])
101011  a44		; a37: branch greater (if AC > 91) skip to mem[a44]		goto(mem[a44]);
			; rotate character
001 011 a1		; a40: AC + mem[a1] (13)				nextChar += mem[a1];
001 111 a6		; a41: compare AC to mem[a6] (90)			if (nextChar <= mem[a6])
101100  a44		; a42: branch less/equal (if AC <= 90) skip to mem[a44]		goto(mem[a44]);
000 100 0000 0110 10	; a43: AC - 26						nextChar -= 26;

110101  0000 0000 11	; a44: trap 3 (Put), print character			print(nextChar);
101000  a20		; a45: jump to mem[a20], jump to start of loop		goto(mem[a20]); //Repeat Loop 
110101  0000 0000 11	; a46: trap 3 (Put), print EOL character		print(EOL);
110101  0000 0000 01	; a47: trap 1 (Halt), stop the program			return 0;