Allow controlling (no) newline when printing and listen to keystrokes

diff --git a/boot.s b/boot.s
index eb115d0324dd6a2e8e83d94aee9d197d71299392..51be5d92dd8ee19426be4092d2aaed2c1e96f46d 100644 (file)
--- a/boot.s
+++ b/boot.s
@@ -1,21 +1,69 @@
        bits 16 ; boot sectors run in real mode
        org 7c00h ; boot sector is loaded at 0x7c00
 
+_start
        mov di, printing_numbers
        call print
 
+       or bl, 1
        mov dx, 0DEADh ; number to print
        call print_word
+       
+       mov di, space
+       call print
+       
+       xor bl, bl
        mov dx, 0BEEFh
        call print_word
 
-       mov di, goodbye
+       mov di, waiting
        call print
 
-       jmp $
+       mov di, keystroke
+       mov bl, 1
+
+.loop
+       mov ah, 0
+       int 16h
+       cmp ah, 1Ch
+       je .enterpressed
+       jmp .continue
+       cmp ah, 0Eh
+       je .backspace
+       jmp .continue
+.enterpressed
+       pusha
+       mov ah, 0Eh
+       mov al, 0Dh
+       int 10h
+       mov al, 0Ah
+       int 10h
+       popa
+       jmp .loop
+.backspace
+       pusha
+       mov ah, 03h
+       mov bh, 0
+       int 10h
+       dec dl
+       mov ah, 02h
+       int 10h
+       mov ah, 0Eh
+       mov al, ' '
+       int 10h
+       mov ah, 02h
+       int 10h
+       popa
+       jmp .loop
+.continue
+       mov [keystroke], al
+       call print
+       jmp .loop
 
-printing_numbers: db "Printing some random hex numbers", 0
-goodbye: db "Thank you for your attention", 0
+printing_numbers db "Printing some random hex numbers", 0
+waiting db "I await keystrokes", 0
+keystroke db "$", 0
+space db " ", 0
 
 %include "print.s"
 

diff --git a/print.s b/print.s
index e1d9bc69d4e1d0cd4341b11213b6ccb8b130d087..3a46c724efa996310ab365d46c3c6f5330e47fb2 100644 (file)
--- a/print.s
+++ b/print.s
@@ -3,28 +3,33 @@
 ; Prints a null terminated string of your choice.
 ; Arguments:
 ;     CS:DI - pointer to the string you want to print
-print:
+;     BL - 0 prints newline, otherwise no
+print
        pusha
        mov ah, 0Eh ; teletype print
-.write2:
+.write2
        mov al, [CURRENT_ADDR] ; get current char and put it in al
        cmp al, 0 ; check if al is null (string terminator)
-       je .done ; if it is, start a new line
+       je .newline ; if it is, start a new line
        int 10h ; otherwise write the char
        inc di ; increment pointer to string
        jmp .write2 ; jump back to this section
-.done:
+.newline
+       cmp bl, 1
+       je .done
        mov al, 0Dh ; carriage return
        int 10h
        mov al, 0Ah ; line feed
        int 10h
+.done
        popa
        ret ; return
 
 ; Prints a word (16-bit value) in hex format.
 ; Arguments:
 ;     DX - word to print
-print_word:
+;     BL - 0 will print a newline, 1 won't
+print_word
        pusha ; push all regs to stack
        mov di, HEX_OUT+5 ; set destination index to last char in HEX_OUT
        mov ax, dx ; copy argument to accumulator
@@ -49,83 +54,83 @@ print_word:
        popa
        ret
 
-.compare:
+.compare
        cmp al, 0 ; compare al with 0
        jne .one ; if not equal, compare with 1
        mov byte [CURRENT_ADDR], '0' ; set character to ASCII 0
        ret ; return
-.one:
+.one
        cmp al, 1
        jne .two
        mov byte [CURRENT_ADDR], '1'
        ret
-.two:
+.two
        cmp al, 2
        jne .three
        mov byte [CURRENT_ADDR], '2'
        ret
-.three:
+.three
        cmp al, 3
        jne .four
        mov byte [CURRENT_ADDR], '3'
        ret
-.four:
+.four
        cmp al, 4
        jne .five
        mov byte [CURRENT_ADDR], '4'
        ret
-.five:
+.five
        cmp al, 5
        jne .six
        mov byte [CURRENT_ADDR], '5'
        ret
-.six:
+.six
        cmp al, 6
        jne .seven
        mov byte [CURRENT_ADDR], '6'
        ret
-.seven:
+.seven
        cmp al, 7
        jne .eight
        mov byte [CURRENT_ADDR], '7'
        ret
-.eight:
+.eight
        cmp al, 8
        jne .nine
        mov byte [CURRENT_ADDR], '8'
        ret
-.nine:
+.nine
        cmp al, 9
        jne .ten
        mov byte [CURRENT_ADDR], '9'
        ret
-.ten:
+.ten
        cmp al, 0Ah
        jne .eleven
        mov byte [CURRENT_ADDR], 'A'
        ret
-.eleven:
+.eleven
        cmp al, 0Bh
        jne .twelve
        mov byte [CURRENT_ADDR], 'B'
        ret
-.twelve:
+.twelve
        cmp al, 0Ch
        jne .thirteen
        mov byte [CURRENT_ADDR], 'C'
        ret
-.thirteen:
+.thirteen
        cmp al, 0Dh
        jne .fourteen
        mov byte [CURRENT_ADDR], 'D'
        ret
-.fourteen:
+.fourteen
        cmp al, 0Eh
        jne .fifteen
        mov byte [CURRENT_ADDR], 'E'
        ret
-.fifteen:
+.fifteen
        mov byte [CURRENT_ADDR], 'F'
        ret
 
-HEX_OUT: db "0x0000", 0
+HEX_OUT db "0x0000", 0