Minor code clean up, and added some convenience to the draw_string function.

kernel/idt.c

@@ -8,7 +8,16 @@ void idt_install()
 {
     idt.size = (sizeof (struct idt_entry) * 256) - 1;
     idt.idt_entries_start = (struct idt_entry *) &idt_entries;
-    
+    // IDT Selector value:
+    // 		0x08 is the code segement we want, which, as defined by the GDT, is the kernel code segment entry in the GDT.
+    //
+    // IDT Flags value:
+    //
+    // Bit: 7 6-5 4-0
+    // 		P DPL Always 01110 (14)
+    // For the kernel ring 8E is chosen
+    // 100 for bits 7-5. 1 (present) 00 (the level in this case ring zero)
+    // 01110 for bits 4-0. This is always set to 14.
     idt_set_gate(&idt_entries[0], (unsigned int) isr0, 0x08, 0x8E);
     idt_set_gate(&idt_entries[1], (unsigned int) isr1, 0x08, 0x8E);
     idt_set_gate(&idt_entries[2], (unsigned int) isr2, 0x08, 0x8E);
@@ -41,7 +50,7 @@ void idt_install()
     idt_set_gate(&idt_entries[29], (unsigned int) isr29, 0x08, 0x8E);
     idt_set_gate(&idt_entries[30], (unsigned int) isr30, 0x08, 0x8E);
     idt_set_gate(&idt_entries[31], (unsigned int) isr31, 0x08, 0x8E);
-    //asm("xchg %bx, %bx");
+    
     load_idt(&idt);
 }
 

kernel/interrupt_handler.c

@@ -3,5 +3,8 @@
 
 void interrupt_handler(struct isr_state stack)
 {
-	write_to_com(COM1_PORT, "Interrupt detected!\n");
+	write_to_com(COM1_PORT, "Divide by zero detected!\n");
+	write_to_com(COM1_PORT, "Halting system!\n");
+	asm("cli");
+	asm("hlt");
 }

kernel/kmain.c

@@ -11,47 +11,28 @@ void kmain()
 {
 	set_serial_baud_rate(COM1_PORT, 0x03);
 	configure_serial_line(COM1_PORT);
+	
 	write_to_com(COM1_PORT, "Set up COM1 for messaging.\n");
 	clear_screen();
 	write_to_com(COM1_PORT, "Clearing screen.\n");
 	print_banner();
-	write_to_com(COM1_PORT, "Displaying OS banner.\n");
-	//draw_rect(20, 5, 50, 7, 0x4, 0xF);
-	draw_rect(0, 5, 5, 13, 0xF, 0x4);
-	draw_rect(5, 8, 10, 10, 0x4, 0xF);
-	draw_rect(10, 5, 15, 13, 0x8, 0x6);
-	draw_rect(20, 5, 25, 7, 0xF, 0x1);
-	draw_rect(20, 8, 25, 13, 0x5, 0x3);
-	set_cursor(0, 14);
-	move_cursor(0, 14);
-	move_cursor(0, 15);
-	draw_string("Test print", 0x8, 0xF);
-	move_cursor(0, 16);
-	draw_string("And now the cursor has been moved to y = 16.", 0x1, 0xF);
-	move_cursor(5, 20);
-	draw_string("Cursor moved over 5 cells and down 4 cells.", 0xF, 0x0);
-	draw_string("And the cursor moves to the end of the string", 0x1, 0xF);
-	draw_string("Now this string should have a newline now:\nAnd now a new line is here.\n", 0xF, 0x0);
-	//draw_rect(20, 5, 50, 7, 0x4, 0xF);
-	//draw_rect(20, 5, 50, 7, 0x4, 0xF);
-	//draw_rect(20, 5, 50, 7, 0x4, 0xF);
-	//draw_s("Hello, World!", 2, 9);
-	//row = 2;
-	///column = 80;
-	//draw_s("And 2nd Row. Now the 3rd row.", 2, 9);
-	move_cursor(0, 3);
-	draw_string("Installing GDT...\n", 0xF, 0x0);
-	write_to_com(COM1_PORT, "Installing the GDT.\n");
+	print_message("Displaying OS banner.\n", 0xF, 0x0);
+	
+	print_message("Installing GDT...\n", 0xF, 0x0);
 	gdt_install();
-
-	//move_cursor(0, 4);
-	//asm("xchg %bx, %bx");	
-	//write_to_com(COM1_PORT, "GDT installed.\n");
+	print_message("GDT installed!\n", 0xF, 0x0);
+	
 	//asm("xchg %bx, %bx"); // Boch's break point
-	//draw_string("Installed GDT\n", 0xf, 0x0);
-	//asm("xchg %bx, %bx");
+	print_message("Installing IDT...\n", 0xF, 0x0);
 	idt_install();
-	write_to_com(COM1_PORT, "IDT installed.\n");
+	print_message("IDT installed.\n", 0xF, 0x0);
+	
 	int i = 5 / 0;
 	asm("hlt");
 }
+
+void print_message(unsigned char* msg, unsigned char fg, unsigned char bg)
+{
+	write_to_com(COM1_PORT, msg);
+	draw_string(msg, fg, bg);
+}

kernel/screen.c

@@ -46,6 +46,8 @@ void print_banner(){
 			}			
 		}
 	}
+	
+	cursor_y = 3;
 }
 //index = (y_value * width_of_screen) + x_value;
 void draw_rect(int start_x, int start_y, int end_x, int end_y, unsigned char fg, unsigned char bg){
@@ -74,13 +76,14 @@ void draw_string(char* string, unsigned char fg, unsigned char bg)
 		
 		if(current_char == '\n'){
 			cursor_y++;
+			cursor_x = 0;
 			continue;
 		}
 		
 		*where = string[i] | attr << 8;
 	}
 	
-	cursor_x = cursor_x + length + 1;
+	if(cursor_x != 0) cursor_x = cursor_x + length + 1;
 }
 
 void set_cursor(unsigned char x, unsigned char y){