diff --git a/kernel/chario.asm b/kernel/chario.asm
new file mode 100644
index 0000000..8993cd1
--- /dev/null
+++ b/kernel/chario.asm
@@ -0,0 +1,18 @@
+putc:
+  pushf
+  push cs
+  call isr_putc
+  ret
+
+isr_getc:
+  xor ax, ax
+  int 0x16
+  test al, al
+  jz isr_getc
+isr_putc:
+  push bx
+  mov ah, 0x0e
+  mov bx, 0x0000
+  int 0x10
+  pop bx
+  iret
diff --git a/kernel/main.asm b/kernel/main.asm
index d5dae45..6c91443 100644
--- a/kernel/main.asm
+++ b/kernel/main.asm
@@ -52,16 +52,6 @@ optrom_init:
 
   retf
 
-putc:
-  push bx
-  push cx
-  mov ah, 0x0e
-  mov bx, 0x0000
-  int 0x10
-  pop cx
-  pop bx
-  ret
-
 announce:
   push ds
   push cs
@@ -87,16 +77,41 @@ start:
 
   call drvtab_create
 
-  int3
+  push cs
+  pop es
+  mov di, isr_dos_main
+  mov ax, 0x21
+  call intr_register
+
+.loop:
+  mov ah, 0x01
+  int 0x21
+  jmp .loop
 
   cli
 .halt:
   hlt
   jmp .halt
 
+isr_dos_main:
+  cmp ah, 0x01
+  je isr_getc
+  cmp ah, 0x02
+  je isr_putc
+isr_error:
+  push bp
+  mov bp, sp
+  ; set carry flag
+  or WORD [SS:BP+6], 1
+  pop bp
+isr_return:
+  iret
+
 %include "intr.asm"
 %include "drvtab.asm"
 
+%include "chario.asm"
+
 %include "printf.inc"
 %include "print.asm"