Question

Write an embedded (continuous input) e-LMC little man program using bubble sort. Zero to end. Constant registers ( R0 = 0, R1 = 1, R2 = 2, R3 = 999)?

Answer 1

ANS:-

Algorith for extended Little Man Computer Program (E-LMC):-

Load the three values into registers R0-R2

// loop 1 step 1
if R1-R0>0
do nothing
else // swap using a temp register
temp=R1
R1=R0
R0=temp
end if
// loop 1 step 2
if R2-R1>0
do nothing
else // swap using a temp register
temp=R2
R2=R1
R1=temp
end if
// loop 2 step 1
if R1-R0>0
do nothing
else // swap using a temp register
temp=R1
R1=R0
R0=temp
end if

Write registers in order: R0,R1,R2.

---------------------

INP //read 1st value
STA 0 // for store
INP // read 2nd value
   STA 1 // store
INP // read 3rd value
STA 2 // store
LDA 1 // LOOP 1, STEP 1:
    SUB 0 //
BRP STEP2 // if R0 and R1 are in order, don't swap them
LDA 1 // Begin swapping registers
STA 3   
LDA 0
STA 1 // R1 = R0
LDA 3
STA 0 //R0 = temp
STEP2 LDA 2 // LOOP 1, STEP 2
SUB 1
BRP STEP3 // If R1 and R2 are in order, don't swap them
LDA 2 // Begin swapping registers
STA 3 // temp =R2
LDA 1
STA 2 //R2=R1
   LDA 3
STA 1 // R1 = temp
STEP3 LDA 1 // LOOP 2, STEP 1
SUB 0
BRP STEP4 // if R0 andR1 are in order, don't swap them
LDA 1 // Begin swapping registers
STA 3 // temp = R1
LDA 0
STA 1 //R1=R0
LDA 3
STO 0 // R0 = temp

STEP4 LDA 0
OUT
   LDA 1
   OUT
LDA 2
OUT
   HLT