You are to design, write, test, and debug a MARIE assembly language program that inputs a
sequence of characters from the set A-Z (capital letters only), stores each character in
memory after it is transformed by the trivial ROT13 cipher, and then, after character input
completes, outputs the transformed characters.
A template source code file ([login to view URL]) is provided with this assignment. Edit this
file to create a program that meets the program specifications. Note that the template
includes instructions to initialize some working values that your program can use. The
template also defines memory locations. You may add data memory locations. The program
can be designed without additional data locations, but it may be necessary to do so for your
For full credit, your solution must perform the functions and satisfy the requirements
a) The first instruction of the program must be placed at location (address) 0x100 (100
hexadecimal) in MARIE’s memory. This is accomplished by following the program
template that is provided.
b) The constant data values (One, ChA, ChZ, ChPer, Val13, Start) should not be
changed by the program. The program can load from these memory locations, but
should not store to them.
c) Transformed input characters must be stored in successive memory locations beginning
at location 0x200 (200 hexadecimal) as indicated in the program template. The
program should store all transformed input characters before any characters are
d) The program should always initialize the values for Ptr in the working data memory
and not rely on the values for these locations that are defined in the assembly source
file. This initialization is done by the provided template file.
e) The program should work for any inputs ‘A’ through ‘Z’ and ‘.’ (a period terminates
input). In the interest of keeping the program simple, the program does not need to
f) When transformed characters are stored and when transformed characters are output,
the program must use a loop and indirect addressing to access the values in the array
of words. Note that variable Ptr is initialized in the template code and should be
used in the loop. You may also define a Count variable to count the number of
characters, but there are also correct designs that do not require a Count variable.
g) The program should operate as follows.
1. A character (A-Z or ‘.’) is input. MarieSim allows the user to input a single
character that is read into the accumulator (AC) with an Input instruction.
2. If character ‘.’ (period) is input, then the input phase ends and the output
phase begins (step 5 below). (The period may be stored in memory to mark the
end of the characters or the characters can be counted to determine how many
transformed characters to output during the output phase.)
4. The character that is input is transformed using the trivial ROT13 cipher (see
5. The transformed character is stored in the next location in the block of
memory beginning at location Start. (Variable Ptr must be updated and
indirect memory addressing must be used.)
6. All transformed characters are output, beginning with the first character that
was transformed. The ‘.’ character is not to be output. (This will require a
loop using variable Ptr and indirect addressing. Note that the number of
characters to output will vary and the program must know when to stop the
output by relying on a ‘.’ or other special character in memory, counting the
number of input characters during the input phase, or some other method.)
7. After all characters are output, the program halts by executing the HALT