!Compile Me!

.vscode/settings.json

@@ -0,0 +1,6 @@
+{
+    "files.associations": {
+        "kmain.h": "c",
+        "io.h": "c"
+    }
+}

Makefile

@@ -1,4 +1,4 @@
-OBJECTS = loader.o kmain.o
+OBJECTS = io.o loader.o kmain.o 
 CC = gcc
 CFLAGS = -m32 -nostdlib -nostdinc -fno-builtin -fno-stack-protector \
 			-nostartfiles -nodefaultlibs -Wall -Wextra -Werror -c

io.c

@@ -0,0 +1,24 @@
+#include "kmain.h"
+#include "io.h"
+
+void fb_write_cell(unsigned int i, char c, unsigned char fg, unsigned char bg) {
+    char *fb = (char *) 0x000B8000;
+    fb[i] = c;
+    fb[i + 1] = ((fg & 0x0F) << 4) | (bg & 0x0F);
+}
+
+void fb_move_cursor(unsigned short pos)
+{
+    outb(FB_COMMAND_PORT, FB_HIGH_BYTE_COMMAND);
+    outb(FB_DATA_PORT, ((pos >> 8) & 0x00FF));
+    outb(FB_COMMAND_PORT, FB_LOW_BYTE_COMMAND);
+    outb(FB_DATA_PORT, pos & 0x00FF);
+}
+
+int write(char *buf, unsigned int len) {
+    for(int i = 0; i <= (int)len; i++) {
+        fb_write_cell((int)(i * 2), buf[i], 0, 15);
+        fb_move_cursor(i);
+    }
+    return 0;
+}

io.h

@@ -0,0 +1,36 @@
+#ifndef INCLUDE_IO_H
+#define INCLUDE_IO_H
+
+/* The I/O ports */
+#define FB_COMMAND_PORT 0x3D4
+#define FB_DATA_PORT 0x3D5
+
+/* The I/O port commands */
+#define FB_HIGH_BYTE_COMMAND 14
+#define FB_LOW_BYTE_COMMAND 15
+
+int write(char *buf, unsigned int len);
+
+void outb(unsigned short port, unsigned char data);
+
+/** fb_write_cell:
+    *  Writes a character with the given foreground and background to position i
+    *  in the framebuffer.
+    * 
+    *  @param i  The location in the framebuffer
+    *  @param c  The character
+    *  @param fg The foreground color
+    *  @param bg The background color
+    *
+    *  @example fb_write_cell(0, 'A', 2, 8);
+    */
+void fb_write_cell(unsigned int i, char c, unsigned char fg, unsigned char bg);
+
+/** fb_move_cursor:
+     *  Moves the cursor of the framebuffer to the given position
+     *
+     *  @param pos The new position of the cursor
+     */
+void fb_move_cursor(unsigned short pos);
+
+#endif /* INCLUDE_IO_H */

io.s

@@ -0,0 +1,11 @@
+    global outb             ; make the label outb visible outside this file
+
+    ; outb - send a byte to an I/O port
+    ; stack: [esp + 8] the data byte
+    ;        [esp + 4] the I/O port
+    ;        [esp    ] return address
+    outb:
+        mov al, [esp + 8]    ; move the data to be sent into the al register
+        mov dx, [esp + 4]    ; move the address of the I/O port into the dx register
+        out dx, al           ; send the data to the I/O port
+        ret                  ; return to the calling function

kmain.c

@@ -1,31 +1,11 @@
-void fb_write_cell(unsigned int i, char c, unsigned char fg, unsigned char bg);
-
-
-int main() {
-    fb_write_cell(0, 'A', 2, 8);
+#include "kmain.h"
+#include "io.h"
+
+int main()
+{
+    fb_write_cell(0, 'A', 0, 15);
+    fb_write_cell(2, 'B', 0, 15);
+    fb_write_cell(4, 'C', 0, 15);
+    fb_move_cursor(6);
     return 0;
-}
-
-/** fb_write_cell:
-    *  Writes a character with the given foreground and background to position i
-    *  in the framebuffer.
-
-    * 
-    *  @param i  The location in the framebuffer
-    *  @param c  The character
-    *  @param fg The foreground color
-    *  @param bg The background color
-    *
-    *  @example fb_write_cell(0, 'A', 2, 8);
-    */
-void fb_write_cell(unsigned int i, char c, unsigned char fg, unsigned char bg) {
-    char *fb = (char *) 0x000B8000;
-    fb[i] = c;
-    fb[i + 1] = ((fg & 0x0F) << 4) | (bg & 0x0F);
-}
-
-struct example {
-    unsigned char config;   /* bit 0 - 7   */
-    unsigned short address; /* bit 8 - 23  */
-    unsigned char index;    /* bit 24 - 31 */
-} __attribute__((packed));
+}

kmain.h

@@ -0,0 +1 @@
+int main();

loader.s

@@ -25,5 +25,7 @@ loader:                         ; the loader label (defined as entry point in li
     mov esp, kernel_stack + KERNEL_STACK_SIZE   ; point esp to the start of the
                                                 ; stack (end of memory area)
     call main
+    
 .loop:
+    
     jmp .loop                   ; loop forever