Added very basic interactive shell.

src/shell.c

@@ -0,0 +1,39 @@
+#include "../include/shell.h"
+#include "../include/scrn.h"
+#include "../include/system.h"
+
+unsigned char* commandbuffer;
+
+void run_shell()
+{
+	puts("Starting interactive shell...\n");
+	commandbuffer[0] = '\0';
+	puts("#>");
+	for(;;);
+}
+
+void key_pressed(unsigned char* character)
+{
+	int len = strlen(commandbuffer);
+	commandbuffer[len] = character;
+	commandbuffer[len + 1] = '\0';
+	putch(character);
+}
+
+void execmd()
+{
+	if(strcmp(commandbuffer, "version"))
+	{
+		puts("\nInteractive Shell Version 0.0.0.1\n");
+	}
+	else if(strcmp(commandbuffer,"cls"))
+	{
+		cls();
+	}
+	else
+	{
+		puts("\nUnknown command\n");
+	}
+	puts("#>");
+	commandbuffer[0] = '\0';
+}