Your program must:
1. Prompt the user for the Course Number (refer to course number description in point 5) by printing on the monitor the string “Type Course Number and press Enter: ” and wait for the user to input a string followed by
2. Your program must then search the list of courses to find a match for the entered course number. The list stores the course number for each course being offered. You will find a match only if the course is in the list. It is possible to not find a match in the list.
3. If your program finds a match, then it must print out “
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4. If your program does not find a match, then it must print out “
5. Unique course numbers are a maximum of 7 characters long and contains only uppercase alphabets and numbers. For example, EE306. Refer to UT’s official course numbering system for more information. The important information related to the specifications of your program is also summarized below.
a. A course can have a one, two, or three letter abbreviations (e.g., M, EE, PHY, etc)
b. Each course is identified by a number made up of three digits, which may be
followed by a letter (e.g., EE307E).
6. Head pointer for the course list is at x4000. In other words, the address of the first node
of the list is at x4000.
The Linked-List
A linked-list is a set of nodes connected to each other via pointers. Each node in the linked-list contains a pointer to (the address of) the next node in the linked-list. This pointer is commonly known as the next-pointer. If the last node contains x0000 as its next pointer, it implies that there is no “next node.” That is, this is the last node. We call x0000 in this context a NULL pointer.
Each node in a linked-list is comprised of k+1 words: one word containing the next-pointer (the pointer to the next node) and k words of data which are being stored by the node. In our case, the
database of courses is implemented as a linked-list with k+1=2. Each node consists of two words in the following order:
1. The next-pointer.
2. A pointer to an ASCII string representing the course number (maximum of 7 Characters long+ NULL).
Recall that a string consists of ASCII codes stored in consecutive memory locations, one ASCII code per location. The string is null-terminated, i.e., the end of a string is signified by the NULL character which is ASCII code 0.
Below is an example database implemented as a linked-list. When you test your program, you can use a database with a similar structure. The test cases that we will use to test your program will be similar to this example.
Figure 1: Example Linked List Structure – Course Offering List
M[Address]
(Next pointer)
(Pointer to Course Number) X4006
X4805 X0000
X480B X0000
X4813 X0000
Figure 2: Contents of Memory
If the input were:
Type Course Number and press Enter: EE307E Then the output message would be: EE307E is not offered this semester.
If the input were:
Type Course Number and press Enter: M308C Then the output message would be: M308C is offered this semester!
Input/Output Requirements
Described below are detailed requirements about the Inputs and Outputs of your program. You should adhere to these guidelines to receive full credit for this assignment.
Input: Your program should prompt the user for the last name from the keyboard, as follows: Print a string EXACTLY “Type Course Number and press Enter: ”. Then wait for the user to input a string followed by
Hint: To continually read from the keyboard without first printing a prompt on the screen, use TRAP x20 (assembler name GETC). That is, for each key you wish to read, the LC-3 operating
system must execute the TRAP x20 service routine. If you follow TRAP x20 with the instruction TRAP x21 (assembler name OUT), the character the user types will be displayed on the screen.
Output: Your program should output one of two strings depending on the outcome of the linked list lookup.
(i) If the course number entered by the user is found in the course listing, print out “
(ii) If the course number entered by the user is not found in the course listing, print out “
Hint: To output a string to the console display, use TRAP x22 (assembler name PUTS). What needs to go into R0 to use this TRAP instruction?
A sample of what your program will produce, when supplied with the input from the user trying to add the course:
EXAMPLE 1:
Type Course Number and press Enter: EE307E EE307E is not offered this semester.
—– Halting the processor —–
EXAMPLE 2:
Type Course Number and press Enter: EE306 EE306 is offered this semester!
—– Halting the processor —-
EXAMPLE 3:
Type Course Number and press Enter: PHY105M PHY105M is offered this semester!
—– Halting the processor —–
Notes & Hints:
1. Your program must start at location x3000.
2. The linked lists is an input to your program. The list is loaded in memory before your program begins to run. Your program will search the list.
3. The pointer to the first node to the list of courses is stored in memory location x4000 before the program execution begins. Further, assume that all the nodes are stored between memory locations x4002 and xFDFF. Make no other assumptions about the location of the nodes. Note that the pointer to the first node may be set to NULL (i.e., 0), indicating that there are no nodes in the list.
4. Your program should NOT make any assumptions about the number of nodes in the list.
5. You may assume that every course in the list have a unique Course Number.
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