HELP WITH THIS LC3 PROGRAM. HOW TO DO FOLLOWING BELOW IN LC3 CODE? Read in the ‘
ID: 3795406 • Letter: H
Question
HELP WITH THIS LC3 PROGRAM. HOW TO DO FOLLOWING BELOW IN LC3 CODE?
Read in the ‘+’ or ‘-‘. If the character is a ‘-‘, remember to make the final result negative (i.e. take the 2’s complement of R5 at the end). If the result is positive then ... don’t.
Convert the string of characters input by the user into the binary number they represent (see examples). To do this, you can follow this algorithm:
Initialize R5 to 0 (DO NOT do this by LD'ing a 0 from memory! There is a much simpler & faster way!)
Convert each digit to binary as it is typed in, and add it to R5; if another digit is entered, multiply R5 by 10, and repeat. Stop when you detect the ENTER (x0A):
For example, if the user types ‘2’, then R5 will contain #2 == b0000 0000 0000 0010
If the user then types a ‘3’, making the string now read “23”, then R5 will contain 2 x 10 + 3 == #23 == b0000 0000 0001 0111
If the user then types ‘4’, making the string read “234”, then R5 will contain 23 x 10 + 4 == #234 == b0000 0000 1110 1010 You must also perform input character validation with this assignment – i.e. reject any non-numeric input character. That is, if the user enters “+23g”, your program should "choke" on the ‘g’, print an error message (see sample output), and start over at the beginning with the initial prompt. However, you do not have to detect overflow in this assignment – we will only test your code with inputs in the range [-32768, +32767].
Expected/ Sample output Output
Prompt
Input a positive or negative decimal number (max 5 digits), followed by ENTER
Newline terminated
Error Message
ERROR INVALID INPUT
Newline terminated Example If the user enters “+7246”, your program should read the ‘+’, ‘7’, ‘2’, ‘4’, ‘6’ and end up with the value b0001 1100 0100 1110 in R5 (which corresponds to the number #7246, or x1C4E). If the users enters “-14237”, your program should read the ‘-‘, ‘1’, ‘4’, ‘2’, ‘3’, ‘7’ and end up with the value #-14237 == xC863 == b11001000 01100011 in R5.
Note: You must echo the digits as they are input (no "ghost writing").
You do not have to output the converted binary number. It should “simply” be sitting happily in R5, where you can check it in simpl.
What should happen when an error occurs?
Output "ERROR INVALID INPUT" and start over, prompting the user for input
Other Errors (output "ERROR INVALID INPUT" and start over):
Nothing entered before ENTER
only sign is entered before ENTER
first character entered is neither a sign nor a digit
REMEMBER: all outputs must be newline terminated
(With postive value)
THIS IS THE GIVEN CODE TO WORK WITH -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
ORIG x3000 ; Program begins here ;------------- ;Instructions ;------------- ;------------------------------- ;INSERT CODE STARTING FROM HERE ;-------------------------------- ;Example of how to Output Intro Message ;LD R0, introMessage ;Output Intro Message ;PUTS ;Example of how to Output Error Message ;LD R0, errorMessage ;Output Error Message ;PUTS HALT ;--------------- ;Data ;--------------- introMessage .FILL x6000 errorMessage .FILL x6100 ;------------ ;Remote data ;------------ .ORIG x6000 ;--------------- ;messages ;--------------- intro .STRINGZ "Input a positive or negative decimal number (max 5 digits), followed by ENTER " ;--------------- ;error_messages ;--------------- .ORIG x6100 error_mes .STRINGZ "ERROR INVALID INPUT " ;--------------- ;END of PROGRAM ;--------------- .END ;------------------- ;PURPOSE of PROGRAM ;-------------------Explanation / Answer
Programming Assignment
Objective
The purpose of this assignment is to illustrate how the .FILL pseudo-op performs the task of translating textual numbers (such as the string “#5392”) into actual numbers (i.e. five thousand three hundred and ninety two, represented of course as a 16-bit two's complement binary value).
High Level Description
Prompt the user to enter in a signed multi-digit number (max 5 digits) from the keyboard. Convert the string of characters entered (as separate ascii codes for decimal numeric digits) into the 16-bit number they represent, and store the result in R5. The range of acceptable values is [-32768, +32767]; the absence of a sign means the number is positive.
Your Tasks
Your program can be broken down into the following tasks:
Read in the ‘+’ or ‘-‘. If the character is a ‘-‘, remember to make the final result negative (i.e. take the 2’s complement of R5 at the end). If the result is positive then ... don’t.
Convert the string of characters input by the user into the binary number they represent (see examples). To do this, you can follow this algorithm:
You must also perform input character validation with this assignment – i.e. reject any non-numeric input character.
That is, if the user enters “+23g”, your program should "choke" on the ‘g’, print an error message (see sample output), and start over at the beginning with the initial prompt.
However, you do not have to detect overflow in this assignment – we will only test your code with inputs in the range [-32768, +32767].
Expected/ Sample output
Output
Example
If the user enters “+7246”, your program should read the ‘+’, ‘7’, ‘2’, ‘4’, ‘6’ and end up with the value b0001 1100 0100 1110 in R5 (which corresponds to the number #7246, or x1C4E).
If the users enters “-14237”, your program should read the ‘-‘, ‘1’, ‘4’, ‘2’, ‘3’, ‘7’ and end up with the value #-14237 == xC863 == b11001000 01100011 in R5.
NOTE: In the following examples, the final result is shown in R2.
This is NOT the register you will be using in your code - use the register specified above!!
(Valid input with a negative sign)
(Valid input with a positive sign)
(Valid input with No sign)
(Invalid input)
Note:
Your code will obviously be tested with a range of different values: Make sure you test your code likewise!
Uh…help?
Try to write this program out in C++/pseudocode before directly tackling it in LC3. Doing so often helps to simplify the process and usually only takes a few minutes to do if you think it through carefully.
To mark the distinction between a positive number and a negative one, set a “flag” (say… R5). If the first character is a ‘-‘, then put a negative number (like #-1) into R5. Otherwise, set R5 to #0 (i.e. non-negative). That way, after you translate the rest of the input characters into the number they represent, you can use a quick IF-statement (like BRn MAKE_NEGATIVE) to toss in the two lines of code it takes to take the 2’s complement of the result.
Submission Instructions
Submit to iLearn for testing, feedback and grading. Some feedback will be sent via E-mail.
Comments/Feedback
In the diff files sent to you in the feedback email, there will be two columns: the left column is the output from your program, and the right is the expected output. Any line that has a | on it means your output did not match the solution. The only line numbers of interest are 13 - 17. You can ignore the rest, even if they have a '|'.
Comment
Meaning
Invalid prompt [1]
Means that your first prompt is wrong. Likely do to not using the provided template.
Tsk Tsk
Did not echo input/incorrect echoing of input [1]
Means that you did not echo the first number entered correctly.
Most common cause is not ending the output with a newline
Invalid Error Message
Means that your error message is wrong. Likely do to not using the provided template.
Tsk Tsk
Invalid prompt [2]
Means that your second prompt is wrong. Likely do to not using the provided template.
Tsk Tsk
Did not echo input/incorrect echoing of input [2]
Means that you did not echo the second number entered correctly.
Most common cause is not ending the output with a newline
Wrong Register Value
The value in Register R5 is not correct. Something is wrong with your algorithm
Did not have ending NEWLINE
Program did not end with a NEWLINE
Rubric
Comics?!Sweet!!
Comment
Meaning
Invalid prompt [1]
Means that your first prompt is wrong. Likely do to not using the provided template.
Tsk Tsk
Did not echo input/incorrect echoing of input [1]
Means that you did not echo the first number entered correctly.
Most common cause is not ending the output with a newline
Invalid Error Message
Means that your error message is wrong. Likely do to not using the provided template.
Tsk Tsk
Invalid prompt [2]
Means that your second prompt is wrong. Likely do to not using the provided template.
Tsk Tsk
Did not echo input/incorrect echoing of input [2]
Means that you did not echo the second number entered correctly.
Most common cause is not ending the output with a newline
Wrong Register Value
The value in Register R5 is not correct. Something is wrong with your algorithm
Did not have ending NEWLINE
Program did not end with a NEWLINE
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