add decent method to get the programs return to interpreter

only had such methods in tests, but they really belong in code
also adding fake values to true ,false and nil

lib/risc/interpreter.rb

@@ -266,7 +266,7 @@ module Risc
         set_instruction(nil)
         return false
       when :died
-        raise "Method #{@registers[:r1].to_string} not found for #{@registers[std_reg(:syscall_1)]}"
+        raise "Method #{@registers[:r1]} not found for #{@registers[std_reg(:syscall_1)]}"
       else
         raise "un-implemented syscall #{name}"
       end
@@ -274,6 +274,15 @@ module Risc
       true
     end
 
+    def get_sys_return
+      val = get_register( std_reg(:syscall_1) ) # syscalls return into syscall_1
+    end
+
+    def run_all
+      tick while(@instruction)
+      clock
+    end
+
     def handle_putstring
       # should test length, syscall_3  (syscall_1 is file_descriptor, ie stdout)
       str = get_register( std_reg(:syscall_2) )