Answer to Question #242963 in Assembler for Israel

Question

Show [x + y/(rs/t) - u] in 3 address, 2 address and 1 address instruction format.

Answer 1

1.One Address Instructions

This uses an implied ACCUMULATOR register for data manipulation. One operand is in the accumulator and the other is in the register or memory location.

 

Expression: x + y/(rs/t) - u

AC       is accumulator

M[]     is any memory location

M[T]   is temporary location

 

LOAD  rs        AC = M[rs]                 ; AC = rs

DIV     t          AC = AC/t                   ; AC = rs/t

STORE T         M[T] = AC                  ; T = rs/t

LOAD  y         AC = M[y]                   ; AC = y

DIV     T         AC = AC/T                  ; AC = y/(rs/t)

ADD    x         AC = AC + M[x]          ; AC = x+ (y/(rs/t))

SUB    u         AC = AC + M[u]          ; AC = x+ y/(rs/t) –u

 

2.Two Address Instructions

Here two addresses can be specified in the instruction. Unlike earlier in one address instruction, the result was stored in the accumulator, here the result can be stored at different locations rather than just accumulators, but require more number of bit to represent address.

 

Expression: x + y/(rs/t) - u

R1, R2 are registers

M[] is any memory location

 

MOV  R1, rs               R1 = M[rs]                ; R1 = rs

DIV     R1, t                 R1 = R1/M[t]            ; R1 = rs/t

MOV  R2, y                R2 = M[y]                 ; R2 = y

DIV     R2, R1              R2 = R2/R1               ; R2 = y/(rs/t)

ADD    R2, M[x]           R2 = R2+M[x]           ; R2 = y/(rs/t) + x

SUB    R2, M[u]           R2 = R2 – M[u]         ; R2 =  x + y/(rs/t) – u

 

3. Three Address Instructions

This has three address field to specify a register or a memory location.

 

Expression: x+(x/(rs/t))-x

R1, R2 are registers

M[] is any memory location

 

SUB    R1, x, y           R1 = M[x] – M[y]       ; R1 = x - u

DIV     R2, rs, t           R2 = M[rs]/M[t]         ; R2 = rs/t

DIV     R2, y, R2         R2 = y/R2                   ; R2 = y/(rs/t)

ADD    R1, R1, R2      R1 = R1 + R2              ; R1 = x + y/(rs/t) – u