Marie Simulator- How to use MarieSim?

Question

I am very new to using Marie simulator, and if anyone could help, it would be great.

the following program:
ORG 200
If, Load X
Subt Y
Skipcond 400
Jump Else
Then, Load Y
Store X
Jump Endif
Else, Load Y
add X
Store Y
Endif, Output
Halt
Two, Dec 2
X, Dec 10
Y, Dec 10
END

From this code, what does this particular part mean? And how do I input a new value to Y? Also, what does first load instruction mean?

Two, Dec 2
X, Dec 10
Y, Dec 10

I am trying to figure this MarieSim out, I would really appreciate it if anyone could help out. thank u.

score 0 · Answer 1 · answered Jun 13 '23 at 08:21

From this code, what does this particular part mean?
Two, Dec 2
X, Dec 10
Y, Dec 10

It declares 3 variables Two, X, Y and set their initial values to 2, 10, 10 respectively. The Dec means that the numbers specified are in Decimal (base 10). These variables can be used anywhere in the program.

And how do I input a new value to Y?

If you want to change the initial value of Y to 50, simply change the number after Dec on this line:

Y, Dec 50

If you want to input the value of Y during execution of program, you must use the Input and Store commands at the start of the program:

ORG 200
Input /take user input
Store Y /store in Y

/ rest of program, including declarations, are unchanged
/ ...

Also, what does first load instruction mean?

Load X means load the value stored in variable X to accumulator. If X contains 10, the value 10 is loaded to accumulator.

For future reference, use the official MARIE instruction set:

 Mnemonic   | Hex | Description
 -----------+-----+-----------------------------------------------
 Add X      |  3  | Add the contents of address X to AC     
 AddI X     |  B  | Add indirect: Use the value at X as the actual 
            |     |   address of the data operand to add to AC
 Clear      |  A  | Put all zeros in AC
 Input      |  5  | Input a value from the keyboard into AC
 Halt       |  7  | Terminate program
 Jump X     |  9  | Load the value of X into PC
 JumpI X    |  C  | Use the value at X as the address to jump to
 JnS X      |  0  | Store the PC at address X and jump to X+1
 Load X     |  1  | Load contents of address X into AC
 LoadI X    |  D  | Load indirect: Use the value at X as the  
            |     |    address of the value to load.
 Output     |  6  | Output the value in AC to the display
 Skipcond X |  8  | Skip next instruction on condition 
            |     | (See note below.)
 Store X    |  2  | Store the contents of AC at address X
 StoreI X   |  E  | Store indirect: Use X the value at X as the 
            |     |    address of where to store the value.
 Subt X     |  4  | Subtract the contents of address X from AC
 -----------------------------------------------------------------
 Note regarding use of SKIPCOND:
   The two address bits closest to the opcode field, bits 10 and 
   11 specify the condition to be tested. If the two address bits 
   are 00, this translates to "skip if the AC is negative". If the 
   two address bits are 01, this translates to "skip if the AC is 
   equal to 0". Finally, if the two address bits are 10 (or 2), 
   this translates to "skip if the AC is greater than 0".       

   Example: the instruction Skipcond 800 will skip the 
            instruction that follows if the AC is 
            greater than 0.
 -----------------------------------------------------------------

Marie Simulator- How to use MarieSim?

1 Answers1