Initial programs from intro chapter

intro/cpu.c

@@ -0,0 +1,19 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include "common.h"
+
+int main(int argc, char *argv[])
+{
+    if (argc != 2) {
+	fprintf(stderr, "usage: cpu <string>\n");
+	exit(1);
+    }
+    char *str = argv[1];
+
+    while (1) {
+	printf("%s\n", str);
+	Spin(1);
+    }
+    return 0;
+}
+