Question

Machine Language -

1. Which of the following assembly code represents the high-level Java code below?

int x;

int i = 5;

if (i < 0)

x = -1;

else

x = 1;

1. @5

D=M

@i

M=D

@BRANCH

M;JLT

@x

M=1

@END

0;JMP

(BRANCH)

@x

M=-1

(END)

@END

0;JMP

2. @5

D=M

@i

M=D

@BRANCH

M;JGE

@x

M=1

@END

0;JMP

(BRANCH)

@x

M=-1

(END)

@END

0;JMP

3. @5

D=M

@i

M=D

@BRANCH

M;JLT

@x

M=1

@END

0;JMP

(BRANCH)

@x

M=-1

(END)

@END

0;JMP

4. @x

D=M

@i

M=D

@BRANCH

M;JGE

@x

M=1

@END

0;JMP

(BRANCH)

@x

M=-1

(END)

@END

0;JMP

2. Write the assembly code that performs the following high-level Java code below:

int n = 5;

int[] arr = new int[n]; // Assume the array points to memory location 100

for (int i = 0; i < n; i++)

arr[i] = 1;

Answer 1

1. No correct answer (option a and c are same here, some mistake. 2nd line code should be D=A)

@5 //A=5

D=A // D=5

@i //A=address of i

M=D //i=5

@BRANCH

M;JLT //if i<0 gto branch

@x

M=1 //x=1

@END

0;JMP //goto END

(BRANCH) //if i<5

@x

M=-1 //x=-1

(END)

@END

0;JMP //stop

Qn2)  

@5

D=A

@n

M=D              //n=5

@i

M=0              //i=0

(LOOP)

@i

D=M

@n

D=D ‐ M            

@END

D; JGE           //if (i-n)>=0 goto end

@arr

D=M

@i

A=D+M

M= 1               //arr[i]=1

@i

M=M+1               //i=i+1

@LOOP

0; JMP               //goto (LOOP)

(END)

@END

0;JMP

Using pointer concepts , arr points to memory address

@5
D=A
@n
M=D              //n=5
@100
D=A
@arr 
M=D            //arr points to  address 100
@i 
M=0              //i=0
(LOOP) 
@i 
D=M 
@n 
D=D ‐ M             
 @END 
D; JGE           //if (i-n)>=0 goto end
@arr
A=M           //address in arr stored in A
M=1     //Mem[address in arr]=Mem[100]=1 in first iteration
@arr
M=M+1  //arr=arr+1, arr values increments to 101,102 etc in each iteration.
@i 
M=M+1               //i=i+1
 @LOOP
 0; JMP               //goto (LOOP)
(END)
@END
0;JMP