Description
Objective
The purpose of this assignment is to write, load and display a grid in LC-3 assembly language. The grid
here is a 8×8 square of spaces where each space can hold Simba, a Hyena, or Simba’s Home. In this
programming assignment, you will learn to write code that interfaces with pre-written code. This
program is part of a sequence that will eventually result in a game called Save Simba. You will use both
Array and Linked-list data structures in the coding of this program.
Details
The Save Simba game involves a jungle made up of a grid of squares (aka gridblocks). For this
assignment, the jungle is a 8×8 grid. The Initial and Home locations along with locations of the Hyenas
are loaded as input to the game. The input is structured as a linked-list. Your job is to complete 3
subroutines that load the jungle information (LOAD_JUNGLE), display the Jungle (DISPLAY_JUNGLE) and
convert grid coordinates to an address (GRID_ADDRESS).
Input
The input is a linked list of records representing gridblocks with 3 fields:
● a link to the next record
● coordinates (row, col) each ranging [0, 7]
● a character indicating gridblock type
○ I (Initial)
○ H (Home)
○ # (Hyena)
Note: Each record contains a field that is the address to the next record. This field is called a link,
which gives this data structure its name, linked-list. The last record will have a link field with an
address of x0000. This is the sentinel that signals the end of the linked list.
An example input file (Jungle.asm) is provided in the starter code. In Jungle.asm, instead of scattering
the linked list all over different parts of memory, all records are stored in a single file linked using labels
instead of addresses. This is done for convenience; your code must work even if the linked list records
are scattered across memory.
Notes:
● The address of the first record in the list will be stored in x5000. (The first record is not at
x5000). This address is referred to as the head of the list.
● There is no defined order in which these records occur. For example, it is possible for the Home
record to be at the head of the linked list.
● There will only be one Initial gridblock and one Home gridblock in the list. You do not have to do
any error checking.
● There may be zero or more Hyena records. If there are no records with # in them, then that
means there are no Hyenas in the jungle.
● When processing the list you need to pay special attention to the Initial and Home records:
○ For the Initial gridblock, you need to put an * in the corresponding entry in the GRID and
set the global variables CURRENT_ROW and CURRENT_COL accordingly. (More on these
variables below.)
○ For the Home gridblock, you need to put an H in the corresponding entry in the GRID
and set the global variables HOME_ROW and HOME_COL accordingly. (More on these
variables below.)
You need to follow all these rules (listed above) for processing the input data when writing your
subroutine called LOAD_JUNGLE.
GRID
The Jungle GRID is a 4×4 grid of spaces defined initially as shown in the left figure of the following table.
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
0 | | | | | | | | |
+-+-+-+-+-+-+-+-+
1 | | | | | | | | |
+-+-+-+-+-+-+-+-+
2 | | | | | | | | |
+-+-+-+-+-+-+-+-+
3 | | | | | | | | |
+-+-+-+-+-+-+-+-+
4 | | | | | | | | |
+-+-+-+-+-+-+-+-+
5 | | | | | | | | |
+-+-+-+-+-+-+-+-+
6 | | | | | | | | |
+-+-+-+-+-+-+-+-+
7 | | | | | | | | |
+-+-+-+-+-+-+-+-+
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
0 | | | | | | | | |
+-+-+-+-+-+-+-+-+
1 | | | | | | | | |
+-+-+-+-+-+-+-+-+
2 | | | | | | | | |
+-+-+-+-+-+-+-+-+
3 | | | | | | | | |
+-+-+-+-+-+-+-+-+
4 | | | | | | | | |
+-+-+-+-+-+-+-+-+
5 | | | | | | | | |
+-+-+-+-+-+-+-+-+
6 | | | | | | | | |
+-+-+-+-+-+-+-+-+
7 | | | | | | | | |
+-+-+-+-+-+-+-+-+
Initial After Load
The GRID itself is a set of .STRINGZ declarations without the row and column numbers (numbers in pink,
above). For example, after loading an input linked list with a Initial location at (2, 1); a Home location at
(1, 2); and three Hyenas at (0, 2), (1, 1), and (3, 1); the GRID looks like the right figure above.
Pre-written Code
The main program that is the engine of your game is provided to you along with the declaration of the
GRID and several variables.
Your Task / Subroutines
Implement the following three subroutines. Two of these subroutines are called by my code, the other
(GRID_ADDRESS) is a utility routine that is called by your code. We will test it though.
● DISPLAY_JUNGLE: This subroutine displays the state of the GRID to the Console.
○ Inputs: None
○ Outputs: None
The jungle GRID is located in memory at the label GRID. It is simply a set of .stringz declarations:
GRID .STRINGZ “+-+-+-+-+-+-+-+-+”
.STRINGZ “| | | | | | | | |”
.STRINGZ “+-+-+-+-+-+-+-+-+”
.STRINGZ “| | | | | | | | |”
.STRINGZ “+-+-+-+-+-+-+-+-+”
.STRINGZ “| | | | | | | | |”
.STRINGZ “+-+-+-+-+-+-+-+-+”
.STRINGZ “| | | | | | | | |”
.STRINGZ “+-+-+-+-+-+-+-+-+”
.STRINGZ “| | | | | | | | |”
.STRINGZ “+-+-+-+-+-+-+-+-+”
.STRINGZ “| | | | | | | | |”
.STRINGZ “+-+-+-+-+-+-+-+-+”
.STRINGZ “| | | | | | | | |”
.STRINGZ “+-+-+-+-+-+-+-+-+”
.STRINGZ “| | | | | | | | |”
.STRINGZ “+-+-+-+-+-+-+-+-+”
Note that each string is null-terminated. The output is not just a simple print of these strings as
can be seen in the figure above. Each column and row number are indicated (shown in pink
above) in the display of the grid on the console. You can create your own .STRINGZ for column
numbers, if you need. You are NOT allowed to modify the GRID or any code provided to you.
● LOAD_JUNGLE: This subroutine reads the input linked list and appropriately populates the
contents of the jungle GRID. See above for the description of the input format.
○ Inputs: R0 – the address of the head of the linked list of gridblock records
○ Outputs: None
○ Purpose: Populates the GRID with the appropriate characters (*, H, #)
Additionally, set the following variables:
■ CURRENT_ROW – initialize with the row of the Initial gridblock
■ CURRENT_COL – initialize with the column of the Initial gridblock
■ HOME_ROW – initialize with the row of the Home gridblock
■ HOME_COL – initialize with the column of the Home gridblock
● GRID_ADDRESS: This subroutine is a key subroutine that both your code and eventually the game
itself depends on. It translates the (row, col) logical GRID coordinates of a gridblock to the
physical address in the GRID memory.
○ Inputs: R1 – row number [0, 7]; R2 – column number [0, 7]
○ Outputs: R0 – corresponding memory address of the gridblock in the GRID
Hint: There are 17 physical rows of characters and only 8 logical rows.
Sample Run
Here is the console output of a sample run of a working solution:
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
0 | | | | | | | | |
+-+-+-+-+-+-+-+-+
1 | | | | | | | | |
+-+-+-+-+-+-+-+-+
2 | | | | | | | | |
+-+-+-+-+-+-+-+-+
3 | | | | | | | | |
+-+-+-+-+-+-+-+-+
4 | | | | | | | | |
+-+-+-+-+-+-+-+-+
5 | | | | | | | | |
+-+-+-+-+-+-+-+-+
6 | | | | | | | | |
+-+-+-+-+-+-+-+-+
7 | | | | | | | | |
+-+-+-+-+-+-+-+-+
Jungle Initial
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
0 | |#| | | | | | |
+-+-+-+-+-+-+-+-+
1 | |#| | | | | | |
+-+-+-+-+-+-+-+-+
2 | |*| | | | | | |
+-+-+-+-+-+-+-+-+
3 | | | | | |#| | |
+-+-+-+-+-+-+-+-+
4 | | | | |#| | |H|
+-+-+-+-+-+-+-+-+
5 | | | | | | |#| |
+-+-+-+-+-+-+-+-+
6 | | | |#| | | | |
+-+-+-+-+-+-+-+-+
7 | | | | | | | | |
+-+-+-+-+-+-+-+-+
Jungle Loaded
—– Halting the processor —–
The top of the output shows the console with the initial state of the jungle before it is populated. The
second part shows the console after the jungle is populated and the program halted.
Submission Instructions
● You must do the programming assignment by yourself. You are permitted to get help from ONLY
the TAs and the instructor.
● The file you submit should be a LC-3 assembly language file named Program3.asm. A starter
version of this file is provided for you. This is the only file you need to submit.
● Submit your completed Program3.asm on Canvas.
