How to get multiple inputs from the emulator

Description

Currently, I'm creating a project where you would have to guess a letter the from the emulator, and I would need the user to enter a random character and the application will let the user know whether they entered a correct character or not. This is what I learnt about how to get an input from a user

Get an input and print it out

In our emulator, if we click the note button, we can see these definitions, we’ll focus on CHRIN and CHROUT today.

 

; ROM routines

define         SCINIT         $ff81 ; initialize/clear screen

define         CHRIN          $ffcf ; input character from keyboard

define         CHROUT         $ffd2 ; output character to screen

define         SCREEN         $ffed ; get screen size

define         PLOT           $fff0 ; get/set cursor coordinates

 

CHRIN will get an input, and CHROUT will print out whatever character currently stored in the accumulator

Basic input/output

If so then if we need an input, we just need to enter this, right?

JSR CHRIN

Well, this will not work because the program will not wait for your input and it will keep running. As the result, your program will stop even before you can press any button.

To deal with this, we would need to create a for/while loop that keeps running , we can do that by:

LOOP: 
        JSR CHRIN
        JMP LOOP

This will make sure that the program will keep checking whether we have an input or not and it will not stop. If we want to print out all the character we enter, we just need to add JSR CHROUT

LOOP: 
        JSR CHRIN
        JSR CHROUT
        JMP LOOP

Now if you run the program, you notice that every time you enter a character, it would appear randomly instead of next to each other. This is because if we don’t enter anything, the compiler will fill that with blank space instead. That’s why we have characters all over the place. Here is how you can make sure that you only enter uppercase letters:

LOOP: 
        JSR CHRIN
        CMP #65 
        BCC LOOP
 
        CMP #91 
        BCS LOOP 
 
        JSR CHROUT
        JMP LOOP

What’s I’m doing here is that I’ll make sure the program will not print out anything if my input is not in the range of 65 to 91, which is A-Z in ASCII table.

 

 

 

 

 

 

 


Comments

Post a Comment

Popular posts from this blog

Project update 1.2

 As the semester coming to an end today, I decided to show what I find and my potential solution for this issue. I wish I was a bit smarter and had more time to work on this issue as it's very interesting to me. Anyways, here are what I found so far that could potentially be beneficial in the future. All the files I mention below will be located in gcc/gcc/config/aarch64. What I found in the GCC repo that may be useful in the future: I believe I located the file that store all the values for the target_versions, it's a file called:  aarch64-option-extensions.def . There is another file called  aarch64-cores.def which included all the aarch64 architectures (in this file, they call those options "core options", if I understand correctly then they are the same). If this is the case, then the update process seems to be a bit easier as we already have the implementation to design for a specific architecture when we use target_version. Last but not least, in aarch64.cc , t...
Read more

Lab 2 - Letter guessing game

Image
 In this lab, I decided to mimic something professor has taught in his recording, which shows how to get input, print output and jump to different branches based on conditions. Assembly is supper difficult for me as I'm really not familiar with the language. As a result, I decide to combine my lab 1 and his instructions to create a letter guessing game. This program will randomly select a letter from A to Z, store it in the memory. The user will guess the letter. If they guess it correctly, a prompt will appear and the screen will become green, else there will be an error prompt followed by an input prompt for retry, and the screen will turn red. Here is the code: ; ROM routines define SCINIT $ff81 ; initialize/clear screen define CHRIN $ffcf ; input character from keyboard define CHROUT $ffd2 ; output character to screen define SCREEN $ffed ; get screen size define PLOT $fff0 ; get/set cursor coordinates define GENERATED_LETTER $0040 define IN...
Read more