显示单个字符的API（1）

20_day/bootpack.h

@@ -30,6 +30,7 @@ void asm_inthandler27(void);
 void asm_inthandler2c(void);
 unsigned int memtest_sub(unsigned int start, unsigned int end);
 void farjmp(int eip, int cs);
+void asm_cons_putchar(void);
 
 /* fifo.c */
 struct FIFO32 {

20_day/console.c

@@ -16,6 +16,7 @@ void console_task(struct SHEET *sheet, unsigned int memtotal)
 	cons.cur_x = 8;
 	cons.cur_y = 28;
 	cons.cur_c = -1;
+	*((int *) 0x0fec) = (int) &cons;
 
 	fifo32_init(&task->fifo, 128, fifobuf, task);
 	timer = timer_alloc();

20_day/hlt.nas

@@ -1,5 +1,6 @@
 [BITS 32]
-		CLI
+		MOV		AL,'A'
+		CALL	0xbe3
 fin:
 		HLT
 		JMP		fin

20_day/naskfunc.nas

@@ -17,8 +17,10 @@
 		GLOBAL	_asm_inthandler27, _asm_inthandler2c
 		GLOBAL	_memtest_sub
 		GLOBAL	_farjmp
+		GLOBAL	_asm_cons_putchar
 		EXTERN	_inthandler20, _inthandler21
 		EXTERN	_inthandler27, _inthandler2c
+		EXTERN	_cons_putchar
 
 [SECTION .text]
 
@@ -209,4 +211,13 @@ mts_fin:
 
 _farjmp:		; void farjmp(int eip, int cs);
 		JMP    FAR [ESP+4]    ; eip, cs
-		RET
+		RET
+
+_asm_cons_putchar:
+		PUSH		1
+		AND			EAX,0xff ; 将AH和EAX的高位置0，将EAX置为已存入字符编码的状态
+		PUSH    EAX
+		PUSH		DWORD [0x0fec] ; 读取内存并PUSH该值
+		CALL		_cons_putchar
+		ADD			ESP,12   ; 将栈中的数据丢弃
+		RET