Add bootable kernel with basic print function

1 files changed, 40 insertions, 0 deletions

diff --git a/kernel.c b/kernel.c
new file mode 100644
index 0000000..1c3a97c
--- /dev/null
+++ b/kernel.c
@@ -0,0 +1,40 @@
+
+#define FRAME_SIZE (80 * 25 * 2) // 80 cols, 25 rows, 2 bytes per char
+
+char *video_ram = (char *) 0xB8000;
+int cursor_pos = 0;
+
+void clear_screen()
+{
+  for (int i = 0; i < FRAME_SIZE; i = i + 2)
+  {
+    video_ram[i] = ' ';
+    video_ram[i + 1] = 0x07;
+  };
+  cursor_pos = 0;
+}
+
+void print(char *msg) 
+{
+  int j = 0;
+  while (msg[j] != '\0')
+  {
+    video_ram[cursor_pos++] = msg[j];
+    video_ram[cursor_pos++] = 0x07;
+    ++j;
+  }
+}
+
+
+void run_kern()
+{
+  clear_screen();
+
+  print("I am a kernel!");
+  print(" another message");
+}
+
+void kernel_entrypoint()
+{
+  run_kern();
+}