Add Syscall: Exit, PutChar, GetCar, PutString, GetString

code/test/start.S

@@ -146,6 +146,43 @@ Yield:
 	j	$31
 	.end Yield
 
+#ifdef CHANGED
+    .globl PutChar
+    .ent    PutChar
+PutChar:
+    addiu $2,$0,SC_PutChar
+	syscall
+	j	$31
+	.end PutChar
+
+    
+    .globl PutString
+    .ent    PutString
+PutString:
+    addiu $2,$0,SC_PutString
+	syscall
+	j	$31
+	.end PutString
+
+    .globl GetChar
+    .ent    GetChar
+
+GetChar:
+    addiu $2,$0,SC_GetChar
+	syscall
+	j	$31
+	.end PutChar
+
+    
+    .globl GetString
+    .ent    GetString
+GetString:
+    addiu $2,$0,SC_GetString
+	syscall
+	j	$31
+	.end GetString
+#endif
+
 /* dummy function to keep gcc happy */
         .globl  __main
         .ent    __main