TASM, Assembly, can't change string, offset

Question

I try to change the string to the other one, but the output I get is broken.

How do I change string to the other one so it doesn't do this:

Intended output:

in rect
under line
out circ

Also, I do not know the purpose of "offset" in the code so it also can be the problem.

Also, I get some warnings when trying to assemble it and I don't know they mean:

The code:

.model small

.data
X    db 0
Y    db 0
var0 db 0

rect        db "out rect",13,10,"$"
rect_plus   db "in rect",13,10,"$"
line        db "under line",13,10,"$"
line_plus   db "above line",13,10,"$"
circ        db "out circ",13,10,"$"
circ_plus   db "in circ",13,10,"$"

.code
main:
    mov ax, @data
    mov ds, ax

    jmp input

    input:
        ...        
        jmp rect_check1

    rect_check1:
        ...        
        jb  rect_check2
        jmp rect_print
    
    rect_check2:
        ...
        jb rect_change
        jmp rect_print
    
    rect_change:
        lea bx, rect;               <============== SOMETHING WRONG HERE
        mov [bx], offset rect_plus; <=========================== OR HERE
    
        jmp rect_print

    rect_print:
        mov dx, offset rect;        <=========================== OR HERE
        mov ah, 09h
        int 21h
    
        jmp line_check
    
    line_check:
        ...
        jb  line_change
        jmp line_print

    line_change:
        lea bx, line;               <=========================== OR HERE
        mov [bx], offset line_plus; <=========================== OR HERE
    
        jmp line_print

    line_print:
        mov dx, offset line;        <=========================== OR HERE
        mov ah, 09h
        int 21h
    
        jmp circ_check
    
    circ_check:
        ...        
        jb  circ_change
        jmp circ_print

    circ_change:
        lea bx, circ;               <=========================== OR HERE
        mov [bx], offset circ_plus; <=========================== OR HERE

        jmp circ_print

    circ_print:
        mov dx, offset circ;        <=========================== OR HERE
        mov ah, 09h
        int 21h

        jmp quit

    quit:
        mov ax, 4c00h
        int 21h
end main

Answer 1

  rect_change:
        lea bx, rect;               <============== SOMETHING WRONG HERE
        mov [bx], offset rect_plus; <=========================== OR HERE
        jmp rect_print

Your logic is wrong here. lea bx, rect loads the offset of string "out rect",13,10,"$" to register bx. The offset in bx is then 0003h. The next instruction tries to overwrite one or two bytes of memory at ds:bx (the letters "o" or "ou") with offset of another string "in rect",13,10,"$" (with binary number 000Eh) which makes no sense. As you didn't specify how many bytes you're going to overwrite, TASM gives you the Warning.

Restructuralize your spaghetti code and make your subprocedures callable (ending with ret), for instance

line_print PROC ; Display the $-terminated string addressed with DS:DX.
        mov ah, 09h
        int 21h
        ret
line_print ENDP

Then, whenever you want to display a string, load its offset to dx and call the subprocedure:

    mov dx,offset rect
    call line_print
    ; check the rectangle
    mov dx,offset rect_plus
    call line_print