3 Programming in code of virtual computer

3.1 Programming in code of One-address Virtual Computer

y=a*b+d*c-f, where

a=5=5h=00000101

b=4=4h=00000100

c=20=14h=00010100

d=-5=-5h=11111011

f=-20=-14h=11101100

Example for VC: 13 bits memory word, 1-address computer, 256 words=>8 bits address. All operations are performed between accumulator (AC) and the 2d operand (A_ex). Result is stored to AC.

A_ex=A₁, if MA=0 (direct addressing mode);

A_ex=(A₁[7…0]), if MA=1 (indirect addressing mode).

Load: (A_ex)=>AC

Save: (AC)=>A_ex

Bits’ numeration				Data
7…….0	13…9	8	7……….0
10	0000	0	0000 0101	a=5
11	0000	0	0000 0100	b=4
12	0000	0	0001 0100	c=20=14h
13	1111	1	1111 1011	d=-5
14	1111	1	1110 1100	f=-20
15	0000	0	0000 0000	y=?
16	0000	0	0000 0000	w=?
Address (hexadecimal)	Code of Operation	MA	A1	Comments
20	0001	0	0001 0011	d=>AC
21	1010	0	0001 0010	AC*c=>AC
22	0010	0	0001 0110	AC=>w
23	0001	0	0001 0001	b=>AC
24	1010	0	0001 0000	AC*a=>AC
25	1000	0	0001 0110	AC+w=>AC
26	1001	0	0001 0100	AC-f=>AC
27	0010	0	0001 0101	AC=>y
28	0000	0	0000 0000	stop

Characteristics:

Data volume V_d =7*13 bits = 91 bites = 12 bytes.

Program volume V_p =9*13 bits = 117 bits = 16 bytes.

Time of execution T_ex =2(+/-)+2(*)+8 (access to memory).

3.2 Programming in code of Two-address Virtual Computer

y=a*b+d*c-f, where

a=5=5h=00000101

b=4=4h=00000100

c=20=14h=00010100

d=-5=-5h=11111011

f=-20=-14h=11101100

Example for VC: 24 bits memory word, 2-address computer, 256 words=>8 bits address

Operation: – is defined by the field MI

00 – (A1)op(A2)=>AC,A2

01 - (A1)op(AC)=>AC

10 - (A1)op(AC)=>A2

11 – (A1) op (A2) =>AC

Mov: (A1)=>A2

Bit’s numeration						Data
7…….0	23…20	19…16		15………8	7……….0
10	0000	0000		0000 0000	0000 0101	a=5
11	0000	0000		0000 0000	0000 0100	b=4
12	0000	0000		0000 0000	0001 0100	c=20=14h
13	1111	1111		1111 1111	1111 1011	d=-5
14	1111	1111		1111 1111	1110 1100	-f=-20
15	0000	0000		0000 0000	0000 0000	y=?
16	0000	0000		0000 0000	0000 0000	w=?
Address (hexadecimal)	Code of Operation	MI	MA	A1	A2	Comments
20	0010	00	00	0001 0110	0001 0011	d=>w
21	1010	00	00	0001 0010	0001 0110	w*c=>w
22	1010	11	00	0001 0000	0001 0001	b*a=>AC
23	1000	01	00	0001 0110	0000 0000	AC+w=>AC
24	1000	10	00	0001 0100	0001 0101	AC+(-f)=>y
25	0000	00	00	0000 0000	0000 0000	stop

Characteristics:

Data volume V_d =7*24 bits = 21 bytes.

Program volume V_p =6*24 bits = 18 bytes.

Time of execution T_ex =2(+/-)+2(*)+10 (access to memory)