Module 6
Dan Works
7-25-1999

a. At what address is the MUL X instruction stored? How is that address
   represented in binary? 

Address 4          00000100


b. What is the binary operation code that corresponds to the symbolic
   instruction LOD? 

   00010100

c. How is the number 2 represented in binary? 

   00000010

d. At what address is variable Y stored, and how is that address
   represented in binary?
 
    10000010

e. Answer question d, this time for variable X. 

   10000001

f. Answer question d, this time for variable W. 

   10000000

g. What are the binary operation codes corresponding to the symbolic
   PIPPIN instructions:

   ADD?   00000000           
   MUL?   00000010
   STO?   00000101


4. Let's reverse the process now to test your understanding. See if you
 can determine the symbolic PIPPIN program that corresponds to the 
 following sequence of binary codes as they would appear in the first
 8 locations of RAM. Use PIPPIN to check your answer.

 
	00010100	00000101       LOD 5
	00000000	10000000       ADD 128
	00000001	10000011       SUB 131
	00000011	10000001       DIV 129
	00000101	10000010       DIV 130
	11111110	00000000       Doesn't appear to be a valid code.
	11111110	00000000       Doesn't appear to be a valid code.
	11111110	00000000       Doesn't appear to be a valid code.


 Now, let's try to parse a few expressions by hand. For each of the 
 statements below, draw its parse tree on a sheet of paper. Then, use
 Rosetta to see if you tree is correct. 

 a. Y = 5 - Z + X        Done -DW
 b. Y = 5 - (Z + X)      Done -DW
 c. Y = 5 - ((Z + X)/2)  Done -DW


 Let's reverse the process again and see if you can match parse trees 
 with their corresponding statements.  For each of the parse trees 
 below, write the statement that it represents. Use Rosetta to confirm
 your answers. 


 A. Y = X - 3 * 2
 B. Y = 2 + (X - 3)
 C:     Y = X - 3 * 2


 For each of the following statements, determine - without using Rosetta!
 - the PIPPIN code that would be generated for it. Then, use Rosetta to
 verify your answers. 

 a. Y = Z * 3 - X 

 LOD Z
 MUL # 3
 SUB X
 STO Y

 b. X = (Y + 5) /2 

 LOD Y
 ADD # 5
 DIV # 2
 STO X

 c. Z = (W * W) + (X * X) 

 LOD W
 MUL W
 STO T1
 LOD X
 MUL X
 ADD T1
 STO Z


 For each of the PIPPIN code segments below, find a statement that
 corresponds to it. Use Rosetta to confirm your suspicions. 

 a.    LOD Z             ANSWER:  X = Z / 2
       DVI #2
       STO X

 b.    LOD Z             ANSWER:  X = (Z / 2) * Y
       DVI #2
       MUL Y
       STO X

 c.    LDI #2            ANSWER:  X = Z / (2 * Y)
       MUL Y
       STO T1
       LOD Z
       DIV T1
       STO X


 8.

 Finally, write and test a PIPPIN program that calculates the average
 of the values in memory locations X, Y, and Z, and stores the result in W. 


 ANSWER:   The equation is:   W = (X + Y + Z) / 3

 The Code is:     LOD X
                  ADD Y
                  ADD Z
                  DIV # 3
                  STO W
___________________________________________________________________



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On page # 3.