adds examples of write/tohost usage

hello-world/hello.c

@@ -1,24 +1,31 @@
 #include <stdint.h>
 #include <stdio.h>
+#include <sys/types.h>
 #include <unistd.h>
 
-#include "platform.h"
 #include "encoding.h"
+#include "platform.h"
+#include <string.h>
 
-int factorial(int i){
-
-	volatile int result = 1;
-	for (int ii = 1; ii <= i; ii++) {
-		result = result * ii;
-	}
-	return result;
+int factorial(int i) {
 
+  volatile int result = 1;
+  for (int ii = 1; ii <= i; ii++) {
+    result = result * ii;
+  }
+  return result;
 }
+extern volatile uint32_t tohost;
+extern volatile uint32_t fromhost;
+int main() {
+  volatile int result = factorial(10);
+  char string[] = "hello world with write";
 
-int main()
-{
-	volatile int result = factorial (10);
-	printf("Factorial is %d\n", result);
-	printf("End of execution");
-	return 0;
+  write(STDOUT_FILENO, string, sizeof(string));
+
+  uint64_t payload[4] = {64, 0, (uintptr_t)string, (strlen(string) + 1)};
+  // tohost = (uint32_t)payload;
+  printf("Factorial is %d", result);
+  //  printf("End of execution");
+  return 0;
 }