This is my first question. The essence of the program is to read the line character by character and prohibit extraneous characters, such as F1, F2, Insert keys etc. or combinations with CTRL (Ctrl+c => heart symbol)
Part of my code below:
main:
mov si, 0
mov ax,@data
mov ds, ax
lea dx,message
mov ah, 09h ;print message
int 21h
mov ax, 40h ; load segment into AX
mov es, ax
read_loop:
mov ah, 00h
test byte ptr es:[17h], 04h ; is CTRL pressed?
jnz read_loop
int 16h
cmp al, 0 ;check ASCII
jne ASCII
mov ah, 00h
int 16h
jmp read_loop
ASCII:
cmp ah, 14
je read_loop
cmp al, 13 ; ENTER?
je next
test byte ptr es:[17h], 04h ; is CTRL pressed?
jnz read_loop
mov str_record[si], al
mov ah, 02h ; display
mov dl, al
int 21h
inc si
cmp si, 40 ;check max_len
je next
jmp read_loop
next:
cmp str_record[0], '$'
je quit
mov al, 3
int 10h
mov di, 0
mov ax, 3
int 10h
mov ah, 02h
mov dh, 2
mov dl, 15
int 10h
I am trying to check ctrl is pressed with Keyboard Shift Status Flags but when I release the key, then all the buttons that I pressed along with CTRL are printed
cmp al, 0 ;check ASCII jne ASCII mov ah, 00h int 16h
Asking a second time after receiving 0 would be typical for how certain DOS keyboard related functions operate. The BIOS keyboard functions don't work that way!
The more practical solution to not allow special keys disturb your results, is to only accept keys that have an ASCII code of 32 or more. The one exception being Enter of course.
read_loop:
mov ah, 00h
int 16h
cmp al, 13 ; ENTER?
je next
cmp al, 32 ;check ASCII
jb read_loop
mov str_record[si], al
mov ah, 02h ; display
mov dl, al
int 21h
inc si
cmp si, 40 ;check max_len
jne read_loop
next: