diff --git a/src/nachos-3.4/code/test/halt b/src/nachos-3.4/code/test/halt
index b6c7190..8d75a65 100644
Binary files a/src/nachos-3.4/code/test/halt and b/src/nachos-3.4/code/test/halt differ
diff --git a/src/nachos-3.4/code/test/matmult b/src/nachos-3.4/code/test/matmult
index 1020242..93ae4ed 100644
Binary files a/src/nachos-3.4/code/test/matmult and b/src/nachos-3.4/code/test/matmult differ
diff --git a/src/nachos-3.4/code/test/shell b/src/nachos-3.4/code/test/shell
index 1640db6..b9af934 100644
Binary files a/src/nachos-3.4/code/test/shell and b/src/nachos-3.4/code/test/shell differ
diff --git a/src/nachos-3.4/code/test/sort b/src/nachos-3.4/code/test/sort
index 4ecebb8..6c05091 100644
Binary files a/src/nachos-3.4/code/test/sort and b/src/nachos-3.4/code/test/sort differ
diff --git a/src/nachos-3.4/code/test/start.s b/src/nachos-3.4/code/test/start.s
index 71c883e..d2a8e23 100644
--- a/src/nachos-3.4/code/test/start.s
+++ b/src/nachos-3.4/code/test/start.s
@@ -130,6 +130,59 @@ Yield:
 	j	$31
 	.end Yield
 
+/************** New inserted code here ****************/
+
+	.globl	ReadInt
+	.ent	ReadInt
+ReadInt:
+	addiu $2,$0,SC_ReadInt
+	syscall
+	j	$31
+	.end ReadInt
+
+	.glob	PrintInt
+	.ent	PrintInt
+PrintInt:
+	addiu $2,$0,SC_PrintInt
+	syscall
+	j	$31
+	.end PrintInt
+
+	.glob	ReadChar
+	.ent	ReadChar
+ReadChar:
+	addiu $2,$0,SC_ReadChar
+	syscall
+	j	$31
+	.end ReadChar
+
+	.glob	PrintChar
+	.ent	PrintChar
+PrintChar:
+	addiu $2,$0,SC_PrintChar
+	syscall
+	j	$31
+	.end PrintChar
+
+	.glob	ReadString
+	.ent	ReadString
+ReadString:
+	addiu	$2,$0,SC_ReadString
+	syscall
+	j	$31
+	.end ReadString
+
+	.glob	PrintString
+	.ent	PrintString
+PrintString:
+	addiu	$2,$0,SC_PrintString
+	syscall
+	j	$31
+	.end PrintString
+
+
+/************** Break of new inserted code ************/
+
 /* dummy function to keep gcc happy */
         .globl  __main
         .ent    __main
diff --git a/src/nachos-3.4/code/userprog/.syscall.h.swp b/src/nachos-3.4/code/userprog/.syscall.h.swp
new file mode 100644
index 0000000..9d55a5a
Binary files /dev/null and b/src/nachos-3.4/code/userprog/.syscall.h.swp differ
diff --git a/src/nachos-3.4/code/userprog/exception.cc b/src/nachos-3.4/code/userprog/exception.cc
index 71773a0..f270605 100644
--- a/src/nachos-3.4/code/userprog/exception.cc
+++ b/src/nachos-3.4/code/userprog/exception.cc
@@ -92,17 +92,27 @@ ExceptionHandler(ExceptionType which)
 			case SC_Halt:
 				interrupt->Halt();
 				break;
+			case SC_ReadInt:
+				break;
+			case SC_PrintInt:
+				break;
+			case SC_ReadChar:
+				break;
+			case SC_PrintChar:
+				break;
+			case SC_ReadString:
+				break;
+			case SC_PrintString:
+				break;
 			default:
 				printf("Unexpected user mode exception %d %d\n", which, type);
 				ASSERT(FALSE);
 				break;
-
 			}
 			break;
 		default:
 			printf("Unexpected user mode exception %d %d\n", which, type);
 			ASSERT(FALSE);
 			break;
-
 	}
 }
diff --git a/src/nachos-3.4/code/userprog/syscall.h b/src/nachos-3.4/code/userprog/syscall.h
index f9d9979..b6fda0d 100644
--- a/src/nachos-3.4/code/userprog/syscall.h
+++ b/src/nachos-3.4/code/userprog/syscall.h
@@ -30,6 +30,26 @@
 #define SC_Fork		9
 #define SC_Yield	10
 
+/******************** New inserted code here *******************/
+/* Our new defined system calls, included:
+ *	SC_ReadInt: read an integer from console
+ *	SC_PrintInt: print an integer to console
+ *	SC_ReadChar: read a character from console
+ *	SC_PrintChar: print a character to console
+ *	SC_ReadString: read a string from console
+ *	SC_PrintString: write a string to console
+ */
+
+#define SC_ReadInt	11
+#define SC_PrintInt	12
+#define SC_ReadChar	13
+#define SC_PrintChar	14
+#define SC_ReadString	15
+#define SC_PrintString	16
+
+/******************* Break of new inserted code ***************/
+
+
 #ifndef IN_ASM
 
 /* The system call interface.  These are the operations the Nachos
@@ -124,6 +144,22 @@ void Fork(void (*func)());
  */
 void Yield();		
 
+/*********************** New inserted code here *****************/
+
+int ReadInt();
+
+void PrintInt();
+
+char ReadChar();
+
+void PrintChar();
+
+void ReadString(char buffer[], int length);
+
+void PrintString(char buffer[]);
+
+/*********************** Break of new inserted code *************/
+
 #endif /* IN_ASM */
 
 #endif /* SYSCALL_H */