I need some help with my MARIE Program as I cannot get it to output the correct
ID: 3911695 • Letter: I
Question
I need some help with my MARIE Program as I cannot get it to output the correct output, the following are the requirements of my program:
1) First, I need to allow the program to receive input from a User, in the form of an ASCII character. And once the user inputs an ASCII character of ".", the input loop would terminate.
2) Second, the user inputted into the program and stored in memory has to be transformed via the Rotate 13 subroutine cipher. I am having an issue with how to correctly call this subroutine in my program, as it is only taking in the last known value, the period.
3) Third, once the subroutine has been called, it will take the user ASCII input and transform each letter by rotating it 13 spaces to the right. It keeps getting stuck in the loop.
4) Fourth, after the ROT13 or Rotate 13 cipher loop has completed, it will then output the transformed characters.
Here is what I have so far:
ORG 100 / Start the program at location 100 hexadecimal
Load Start / Initialize character pointer to start of block
UserI, Input
Store Ptr
Load Ptr
Subt ChPe
Skipcond 400
Jump UserI
LoadI Ptr / Put 'A' in AC
Store InVal / Store value to be transformed into InVal
Jns ROT13 / Jump to the ROT13 subroutine
/ Upon return, the transformed character is in AC
ROT13, HEX 0
Load InVal / Get character
Add Val13 / Add 13
Store Hold / Save it
Subt ChZ / Check if modulo adjust is needed (past 'Z')
Skipcond 800 / No adjust needed if past 'Z'
Jump NoAdj
Add ChA
Jump Done / Result is in AC
NoAdj, Load Hold
Store Ptr
Done, JumpI ROT13 / Return with result in AC
OCycle, LoadI Ptr
Store Ptr
Subt ChPe
Skipcond 400
Jump Cont
Halt
Cont, Load Ptr
Output
Load Ptr
Add One
Store Ptr
Jump OCycle
/ -----
/ Constants (the program should not write to these locations)
/ -----
ChA, HEX 0041 / Constant value 'A' for modulo adjust in subroutine
ChZ, HEX 005A / Constant value 'Z' for modulo check in subroutine
ChPe, HEX 2E / Constant period character that marks end of input
Val13, DEC 13 / Constant rotate value of 13 for subroutine
One, HEX 1 / Constant value 1
Start, HEX 200 / Constant address for start of character block
/ -----
/ Data area (these locations are for reading and writing)
/ -----
InVal, HEX 0 / Reserved for subroutine input value
Hold, HEX 0 / Reserved for temporary variable for subroutine
Ptr, HEX 0 / Reserved for character pointer
Explanation / Answer
/ *****
ORG 100 / Start the program at location 100 hexadecimal
/ -----
/ Input characters, transform, and store in memory until '.' is input
/ -----
Load Start / Initialize character pointer to start of block
Store Ptr
/>>>>> Add code to accomplish the input and output phases. <<<<<
Input InVal
/>>>>> Here's an example of how subroutine ROT13 is called. <<<<<
/>>>>> We'll just transform 'A' in this example then halt. <<<<<
Load ChA / Put 'A' in AC
Store InVal / Store value to be transformed into InVal
Jns ROT13 / Jump to the ROT13 subroutine
/ Upon return, the transformed character is in AC
Halt
/ -----
/ Rotate-13 subroutine: Apply ROT13 to input character in location InVal and return in AC
/ -----
/>>>>> WARNING: This subroutine *almost* works. You need to fix a bug.
ROT13, HEX 0
Load InVal / Get character
Add Val13 / Add 13
Store Hold / Save it
Subt ChZ / Check if modulo adjust is needed (past 'Z')
Skipcond 800 / No adjust needed if past 'Z'
Jump NoAdj
Add ChA / Add 'A' back to difference to perform modulo
Jump Done / Result is in AC
NoAdj, Load Hold / No adjust needed, get result
Done, JumpI ROT13 / Return with result in AC
/ -----
/ Constants (the program should not write to these locations)
/ -----
ChA, HEX 0041 / Constant value 'A' for modulo adjust in subroutine
ChZ, HEX 005A / Constant value 'Z' for modulo check in subroutine
ChPe, HEX 2E / Constant period character that marks end of input
Val13, DEC 13 / Constant rotate value of 13 for subroutine
One, HEX 1 / Constant value 1
Start, HEX 200 / Constant address for start of character block
/ -----
/ Data area (these locations are for reading and writing)
/ -----
InVal, HEX 0 / Reserved for subroutine input value
Hold, HEX 0 / Reserved for temporary variable for subroutine
Ptr, HEX 0 / Reserved for character pointer