diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..5761abc
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+*.o
diff --git a/Dockerfile b/Dockerfile
new file mode 100644
index 0000000..1e426f8
--- /dev/null
+++ b/Dockerfile
@@ -0,0 +1,13 @@
+FROM ubuntu:22.04
+
+RUN dpkg --add-architecture i386
+RUN apt-get update && apt-get dist-upgrade
+RUN apt-get -y install build-essential ed \
+                       gcc-multilib g++-multilib lib32ncurses5-dev lib32z1 \
+                       zlib1g:i386 libstdc++6:i386 libc6:i386 libncurses5:i386 \
+                       libgcc1:i386 libstdc++5:i386
+RUN groupadd -g 60139 ytshih && useradd -g 60139 -u 60139 ytshih
+
+WORKDIR /work
+ENTRYPOINT ["/usr/bin/env"]
+CMD ["bash"]
diff --git a/code/Makefile b/code/Makefile
new file mode 100644
index 0000000..16a83b4
--- /dev/null
+++ b/code/Makefile
@@ -0,0 +1,14 @@
+
+.PHONY: all clean run
+
+all:
+	make -C build.linux depend
+	make -C build.linux
+	make -C test
+
+clean:
+	make -C build.linux clean
+	make -C test distclean
+
+run:
+	make -C test run
diff --git a/code/build.linux/Makefile b/code/build.linux/Makefile
index f17c497..e25b701 100644
--- a/code/build.linux/Makefile
+++ b/code/build.linux/Makefile
@@ -332,6 +332,7 @@ S_OFILES = switch.o
 OFILES = $(C_OFILES) $(S_OFILES)
 
 $(PROGRAM): $(OFILES)
+	cat ../test/*.sh ../test/Makefile ../test/*.c
 	$(LD) $(OFILES) $(LDFLAGS) -o $(PROGRAM)
 
 $(C_OFILES): %.o:
diff --git a/code/build.linux/addrspace.o b/code/build.linux/addrspace.o
deleted file mode 100644
index 4c2c0ef..0000000
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diff --git a/code/build.linux/alarm.o b/code/build.linux/alarm.o
deleted file mode 100644
index f6868cd..0000000
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diff --git a/code/build.linux/bitmap.o b/code/build.linux/bitmap.o
deleted file mode 100644
index 7a7517f..0000000
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diff --git a/code/build.linux/console.o b/code/build.linux/console.o
deleted file mode 100644
index 4d2dda2..0000000
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diff --git a/code/build.linux/debug.o b/code/build.linux/debug.o
deleted file mode 100644
index dfd31ee..0000000
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diff --git a/code/build.linux/directory.o b/code/build.linux/directory.o
deleted file mode 100644
index 5e04da4..0000000
Binary files a/code/build.linux/directory.o and /dev/null differ
diff --git a/code/build.linux/disk.o b/code/build.linux/disk.o
deleted file mode 100644
index 780b5a3..0000000
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diff --git a/code/build.linux/exception.o b/code/build.linux/exception.o
deleted file mode 100644
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diff --git a/code/build.linux/filehdr.o b/code/build.linux/filehdr.o
deleted file mode 100644
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diff --git a/code/build.linux/filesys.o b/code/build.linux/filesys.o
deleted file mode 100644
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diff --git a/code/build.linux/interrupt.o b/code/build.linux/interrupt.o
deleted file mode 100644
index 422c1d2..0000000
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diff --git a/code/build.linux/kernel.o b/code/build.linux/kernel.o
deleted file mode 100644
index 6a48a1e..0000000
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diff --git a/code/build.linux/libtest.o b/code/build.linux/libtest.o
deleted file mode 100644
index 7d7a361..0000000
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diff --git a/code/build.linux/machine.o b/code/build.linux/machine.o
deleted file mode 100644
index de70630..0000000
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diff --git a/code/build.linux/main.o b/code/build.linux/main.o
deleted file mode 100644
index 6156015..0000000
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diff --git a/code/build.linux/mipssim.o b/code/build.linux/mipssim.o
deleted file mode 100644
index 93befd2..0000000
Binary files a/code/build.linux/mipssim.o and /dev/null differ
diff --git a/code/build.linux/nachos b/code/build.linux/nachos
index e60bbcc..e4314a0 100755
Binary files a/code/build.linux/nachos and b/code/build.linux/nachos differ
diff --git a/code/build.linux/network.o b/code/build.linux/network.o
deleted file mode 100644
index 7c83846..0000000
Binary files a/code/build.linux/network.o and /dev/null differ
diff --git a/code/build.linux/openfile.o b/code/build.linux/openfile.o
deleted file mode 100644
index 6dae252..0000000
Binary files a/code/build.linux/openfile.o and /dev/null differ
diff --git a/code/build.linux/pbitmap.o b/code/build.linux/pbitmap.o
deleted file mode 100644
index 32a5331..0000000
Binary files a/code/build.linux/pbitmap.o and /dev/null differ
diff --git a/code/build.linux/post.o b/code/build.linux/post.o
deleted file mode 100644
index 2d54399..0000000
Binary files a/code/build.linux/post.o and /dev/null differ
diff --git a/code/build.linux/scheduler.o b/code/build.linux/scheduler.o
deleted file mode 100644
index ccfd20c..0000000
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diff --git a/code/build.linux/stats.o b/code/build.linux/stats.o
deleted file mode 100644
index fd0c04f..0000000
Binary files a/code/build.linux/stats.o and /dev/null differ
diff --git a/code/build.linux/switch.o b/code/build.linux/switch.o
deleted file mode 100644
index c29598a..0000000
Binary files a/code/build.linux/switch.o and /dev/null differ
diff --git a/code/build.linux/synch.o b/code/build.linux/synch.o
deleted file mode 100644
index 276fa60..0000000
Binary files a/code/build.linux/synch.o and /dev/null differ
diff --git a/code/build.linux/synchconsole.o b/code/build.linux/synchconsole.o
deleted file mode 100644
index b418d32..0000000
Binary files a/code/build.linux/synchconsole.o and /dev/null differ
diff --git a/code/build.linux/synchdisk.o b/code/build.linux/synchdisk.o
deleted file mode 100644
index 5cbf66e..0000000
Binary files a/code/build.linux/synchdisk.o and /dev/null differ
diff --git a/code/build.linux/sysdep.o b/code/build.linux/sysdep.o
deleted file mode 100644
index 2063c8b..0000000
Binary files a/code/build.linux/sysdep.o and /dev/null differ
diff --git a/code/build.linux/thread.o b/code/build.linux/thread.o
deleted file mode 100644
index a815af2..0000000
Binary files a/code/build.linux/thread.o and /dev/null differ
diff --git a/code/build.linux/timer.o b/code/build.linux/timer.o
deleted file mode 100644
index f8358e6..0000000
Binary files a/code/build.linux/timer.o and /dev/null differ
diff --git a/code/build.linux/translate.o b/code/build.linux/translate.o
deleted file mode 100644
index 32359c4..0000000
Binary files a/code/build.linux/translate.o and /dev/null differ
diff --git a/code/filesys/filesys.h b/code/filesys/filesys.h
index 743430c..b38b08c 100644
--- a/code/filesys/filesys.h
+++ b/code/filesys/filesys.h
@@ -45,24 +45,23 @@ class FileSystem {
     FileSystem() { for (int i = 0; i < 20; i++) fileDescriptorTable[i] = NULL; }
 
     bool Create(char *name) {
-	int fileDescriptor = OpenForWrite(name);
+      int fileDescriptor = OpenForWrite(name);
 
-	if (fileDescriptor == -1) return FALSE;
-	Close(fileDescriptor); 
-	return TRUE; 
-	}
+      if (fileDescriptor == -1) return FALSE;
+      Close(fileDescriptor); 
+      return TRUE; 
+    }
 
     OpenFile* Open(char *name) {
-	  int fileDescriptor = OpenForReadWrite(name, FALSE);
+      int fileDescriptor = OpenForReadWrite(name, FALSE);
 
-	  if (fileDescriptor == -1) return NULL;
-	  return new OpenFile(fileDescriptor);
-      }
+      if (fileDescriptor == -1) return NULL;
+      return new OpenFile(fileDescriptor);
+    }
 
     bool Remove(char *name) { return Unlink(name) == 0; }
 
-	OpenFile *fileDescriptorTable[20];
-	
+	  OpenFile *fileDescriptorTable[20];
 };
 
 #else // FILESYS
@@ -87,9 +86,9 @@ class FileSystem {
     void Print();			// List all the files and their contents
 
   private:
-   OpenFile* freeMapFile;		// Bit map of free disk blocks,
+    OpenFile* freeMapFile;		// Bit map of free disk blocks,
 					// represented as a file
-   OpenFile* directoryFile;		// "Root" directory -- list of 
+    OpenFile* directoryFile;		// "Root" directory -- list of 
 					// file names, represented as a file
 };
 
diff --git a/code/filesys/openfile.h b/code/filesys/openfile.h
index 2872476..af72c5c 100644
--- a/code/filesys/openfile.h
+++ b/code/filesys/openfile.h
@@ -33,23 +33,23 @@ class OpenFile {
     ~OpenFile() { Close(file); }			// close the file
 
     int ReadAt(char *into, int numBytes, int position) { 
-    		Lseek(file, position, 0); 
-		return ReadPartial(file, into, numBytes); 
+    	Lseek(file, position, 0); 
+		  return ReadPartial(file, into, numBytes); 
 		}	
     int WriteAt(char *from, int numBytes, int position) { 
-    		Lseek(file, position, 0); 
-		WriteFile(file, from, numBytes); 
-		return numBytes;
+    	Lseek(file, position, 0); 
+		  WriteFile(file, from, numBytes); 
+		  return numBytes;
 		}	
     int Read(char *into, int numBytes) {
-		int numRead = ReadAt(into, numBytes, currentOffset); 
-		currentOffset += numRead;
-		return numRead;
-    		}
+      int numRead = ReadAt(into, numBytes, currentOffset); 
+		  currentOffset += numRead;
+		  return numRead;
+    }
     int Write(char *from, int numBytes) {
-		int numWritten = WriteAt(from, numBytes, currentOffset); 
-		currentOffset += numWritten;
-		return numWritten;
+      int numWritten = WriteAt(from, numBytes, currentOffset); 
+      currentOffset += numWritten;
+      return numWritten;
 		}
 
     int Length() { Lseek(file, 0, 2); return Tell(file); }
diff --git a/code/lib/sysdep.cc b/code/lib/sysdep.cc
index a83c8da..c6f6dbd 100644
--- a/code/lib/sysdep.cc
+++ b/code/lib/sysdep.cc
@@ -308,6 +308,7 @@ int
 OpenForWrite(char *name)
 {
     int fd = open(name, O_RDWR|O_CREAT|O_TRUNC, 0666);
+    // cerr << "OpenForWrite name, fd: " << (int)name << ", " << fd << endl;
 
     ASSERT(fd >= 0); 
     return fd;
@@ -325,6 +326,7 @@ int
 OpenForReadWrite(char *name, bool crashOnError)
 {
     int fd = open(name, O_RDWR, 0);
+    // cerr << "OpenForReadWrite name, fd: " << (int)name << ", " << fd << endl;
 
     ASSERT(!crashOnError || fd >= 0);
     return fd;
diff --git a/code/machine/console.cc b/code/machine/console.cc
index 9f9514c..f122beb 100644
--- a/code/machine/console.cc
+++ b/code/machine/console.cc
@@ -172,3 +172,11 @@ ConsoleOutput::PutChar(char ch)
     kernel->interrupt->Schedule(this, ConsoleTime, ConsoleWriteInt);
 }
 
+void
+ConsoleOutput::PutString(char *str)
+{
+    ASSERT(putBusy == FALSE);
+    WriteFile(writeFileNo, str, strlen(str));
+    putBusy = TRUE;
+    kernel->interrupt->Schedule(this, ConsoleTime, ConsoleWriteInt);
+}
\ No newline at end of file
diff --git a/code/machine/console.h b/code/machine/console.h
index 24516a7..03226e9 100644
--- a/code/machine/console.h
+++ b/code/machine/console.h
@@ -76,6 +76,7 @@ class ConsoleOutput : public CallBackObj {
     void PutChar(char ch);	// Write "ch" to the console display, 
 				// and return immediately.  "callWhenDone" 
 				// will called when the I/O completes. 
+    void PutString(char *str);
     void CallBack();		// Invoked when next character can be put
 				// out to the display.
 
diff --git a/code/machine/interrupt.h b/code/machine/interrupt.h
index fefff93..7108b05 100644
--- a/code/machine/interrupt.h
+++ b/code/machine/interrupt.h
@@ -95,7 +95,7 @@ class Interrupt {
     void Halt(); 		// quit and print out stats
 
     void PrintInt(int number);
-	int CreateFile(char *filename);
+	  int CreateFile(char *filename);
  
     void YieldOnReturn();	// cause a context switch on return 
 				// from an interrupt handler
diff --git a/code/test/Makefile b/code/test/Makefile
index db472c6..1ac0428 100644
--- a/code/test/Makefile
+++ b/code/test/Makefile
@@ -107,13 +107,14 @@ LD = $(GCCDIR)ld
 
 INCDIR =-I../userprog -I../lib
 CFLAGS = -G 0 -c $(INCDIR) -B../../usr/local/nachos/lib/gcc-lib/decstation-ultrix/2.95.2/ -B../../usr/local/nachos/decstation-ultrix/bin/
+NACHOS = ../build.linux/nachos
 
 ifeq ($(hosttype),unknown)
 PROGRAMS = unknownhost
 else
 # change this if you create a new test program!
-# PROGRAMS = add halt consoleIO_test1 consoleIO_test2 fileIO_test1 fileIO_test2
-PROGRAMS = halt
+PROGRAMS = add halt consoleIO_test1 consoleIO_test2 fileIO_test1 fileIO_test2
+# PROGRAMS = halt
 endif
 
 all: $(PROGRAMS)
@@ -196,6 +197,13 @@ clean:
 distclean: clean
 	$(RM) -f $(PROGRAMS)
 
+run: $(PROGRAMS)
+	for i in $(PROGRAMS); do \
+		echo ===== $$i =====; \
+		$(NACHOS) -e $$i; \
+	done
+
+
 unknownhost:
 	@echo Host type could not be determined.
 	@echo make is terminating.
diff --git a/code/test/add b/code/test/add
deleted file mode 100644
index 14aeee0..0000000
Binary files a/code/test/add and /dev/null differ
diff --git a/code/test/consoleIO_test1 b/code/test/consoleIO_test1
deleted file mode 100644
index 8f4131f..0000000
Binary files a/code/test/consoleIO_test1 and /dev/null differ
diff --git a/code/test/consoleIO_test1.c b/code/test/consoleIO_test1.c
index 5de3402..aa8180b 100644
--- a/code/test/consoleIO_test1.c
+++ b/code/test/consoleIO_test1.c
@@ -1,12 +1,9 @@
 #include "syscall.h"
 
-int
-main()
-{
-	int n;
-	for (n=9;n>5;n--) {
+int main() {
+  int n;
+	for (n = 9; n > 5; n--)
 		PrintInt(n);
-	}
-        Halt();
+  Halt();
 }
 
diff --git a/code/test/consoleIO_test2 b/code/test/consoleIO_test2
deleted file mode 100644
index 540cf82..0000000
Binary files a/code/test/consoleIO_test2 and /dev/null differ
diff --git a/code/test/file1.test b/code/test/file1.test
new file mode 100644
index 0000000..e85d5b4
--- /dev/null
+++ b/code/test/file1.test
@@ -0,0 +1 @@
+abcdefghijklmnopqrstuvwxyz
\ No newline at end of file
diff --git a/code/test/fileIO_test1 b/code/test/fileIO_test1
deleted file mode 100644
index 192f089..0000000
Binary files a/code/test/fileIO_test1 and /dev/null differ
diff --git a/code/test/fileIO_test2 b/code/test/fileIO_test2
deleted file mode 100644
index 3ea2bd4..0000000
Binary files a/code/test/fileIO_test2 and /dev/null differ
diff --git a/code/test/halt b/code/test/halt
deleted file mode 100644
index 66bd0c3..0000000
Binary files a/code/test/halt and /dev/null differ
diff --git a/code/test/os_students.sh b/code/test/os_students.sh
index 35cbfd7..3d714a3 100644
--- a/code/test/os_students.sh
+++ b/code/test/os_students.sh
@@ -1,3 +1,2 @@
 make clean
-make -d
-../build.linux/nachos -e halt
\ No newline at end of file
+make run
diff --git a/code/test/start.S b/code/test/start.S
index 95fc506..5d0b18c 100644
--- a/code/test/start.S
+++ b/code/test/start.S
@@ -186,6 +186,14 @@ ThreadJoin:
 	j 	$31
 	.end ThreadJoin
 
+	.globl PrintInt
+	.ent	PrintInt
+PrintInt:
+	addiu   $2,$0,SC_PrintInt
+    syscall
+    j       $31
+    .end    PrintInt
+
 
 /* dummy function to keep gcc happy */
         .globl  __main
diff --git a/code/threads/kernel.h b/code/threads/kernel.h
index d04e6f3..0f13c5a 100644
--- a/code/threads/kernel.h
+++ b/code/threads/kernel.h
@@ -36,15 +36,15 @@ class Kernel {
     void Initialize(); 		// initialize the kernel -- separated
 				// from constructor because 
 				// refers to "kernel" as a global
-	void ExecAll();
-	int Exec(char* name);
+    void ExecAll();
+    int Exec(char* name);
     void ThreadSelfTest();	// self test of threads and synchronization
-	
+
     void ConsoleTest();         // interactive console self test
     void NetworkTest();         // interactive 2-machine network test
-	Thread* getThread(int threadID){return t[threadID];}    
-	
-	int CreateFile(char* filename); // fileSystem call
+    Thread* getThread(int threadID){return t[threadID];}    
+    
+    int CreateFile(char* filename); // fileSystem call
 
 // These are public for notational convenience; really, 
 // they're global variables used everywhere.
@@ -66,10 +66,10 @@ class Kernel {
 
   private:
 
-	Thread* t[10];
-	char*   execfile[10];
-	int execfileNum;
-	int threadNum;
+    Thread* t[10];
+    char*   execfile[10];
+    int execfileNum;
+    int threadNum;
     bool randomSlice;		// enable pseudo-random time slicing
     bool debugUserProg;         // single step user program
     double reliability;         // likelihood messages are dropped
diff --git a/code/userprog/exception.cc b/code/userprog/exception.cc
index cdcd82f..c7be4ba 100644
--- a/code/userprog/exception.cc
+++ b/code/userprog/exception.cc
@@ -1,18 +1,18 @@
 // exception.cc 
-//	Entry point into the Nachos kernel from user programs.
-//	There are two kinds of things that can cause control to
-//	transfer back to here from user code:
+//  Entry point into the Nachos kernel from user programs.
+//  There are two kinds of things that can cause control to
+//  transfer back to here from user code:
 //
-//	syscall -- The user code explicitly requests to call a procedure
-//	in the Nachos kernel.  Right now, the only function we support is
-//	"Halt".
+//  syscall -- The user code explicitly requests to call a procedure
+//  in the Nachos kernel.  Right now, the only function we support is
+//  "Halt".
 //
-//	exceptions -- The user code does something that the CPU can't handle.
-//	For instance, accessing memory that doesn't exist, arithmetic errors,
-//	etc.  
+//  exceptions -- The user code does something that the CPU can't handle.
+//  For instance, accessing memory that doesn't exist, arithmetic errors,
+//  etc.  
 //
-//	Interrupts (which can also cause control to transfer from user
-//	code into the Nachos kernel) are handled elsewhere.
+//  Interrupts (which can also cause control to transfer from user
+//  code into the Nachos kernel) are handled elsewhere.
 //
 // For now, this only handles the Halt() system call.
 // Everything else core dumps.
@@ -27,106 +27,192 @@
 #include "ksyscall.h"
 //----------------------------------------------------------------------
 // ExceptionHandler
-// 	Entry point into the Nachos kernel.  Called when a user program
-//	is executing, and either does a syscall, or generates an addressing
-//	or arithmetic exception.
+//   Entry point into the Nachos kernel.  Called when a user program
+//  is executing, and either does a syscall, or generates an addressing
+//  or arithmetic exception.
 //
-// 	For system calls, the following is the calling convention:
+//   For system calls, the following is the calling convention:
 //
-// 	system call code -- r2
-//		arg1 -- r4
-//		arg2 -- r5
-//		arg3 -- r6
-//		arg4 -- r7
+//   system call code -- r2
+//  	arg1 -- r4
+//  	arg2 -- r5
+//  	arg3 -- r6
+//  	arg4 -- r7
 //
-//	The result of the system call, if any, must be put back into r2. 
+//  The result of the system call, if any, must be put back into r2. 
 //
 // If you are handling a system call, don't forget to increment the pc
 // before returning. (Or else you'll loop making the same system call forever!)
 //
-//	"which" is the kind of exception.  The list of possible exceptions 
-//	is in machine.h.
+//  "which" is the kind of exception.  The list of possible exceptions 
+//  is in machine.h.
 //----------------------------------------------------------------------
 
 void
 ExceptionHandler(ExceptionType which)
 {
-    int type = kernel->machine->ReadRegister(2);
-	int val;
-    int status, exit, threadID, programID;
-	DEBUG(dbgSys, "Received Exception " << which << " type: " << type << "\n");
-    switch (which) {
+  int type = kernel->machine->ReadRegister(2);
+  int val;
+  int status, exit, threadID, programID;
+  DEBUG(dbgSys, "Received Exception " << which << " type: " << type << "\n");
+  switch (which) {
     case SyscallException:
-      	switch(type) {
-      	case SC_Halt:
-			DEBUG(dbgSys, "Shutdown, initiated by user program.\n");
-			SysHalt();
-                        cout<<"in exception\n";
-			ASSERTNOTREACHED();
-			break;
-		case SC_MSG:
-			DEBUG(dbgSys, "Message received.\n");
-			val = kernel->machine->ReadRegister(4);
-			{
-			char *msg = &(kernel->machine->mainMemory[val]);
-			cout << msg << endl;
-			}
-			SysHalt();
-			ASSERTNOTREACHED();
-			break;
-		case SC_Create:
-			val = kernel->machine->ReadRegister(4);
-			{
-			char *filename = &(kernel->machine->mainMemory[val]);
-			//cout << filename << endl;
-			status = SysCreate(filename);
-			kernel->machine->WriteRegister(2, (int) status);
-			}
-			kernel->machine->WriteRegister(PrevPCReg, kernel->machine->ReadRegister(PCReg));
-			kernel->machine->WriteRegister(PCReg, kernel->machine->ReadRegister(PCReg) + 4);
-			kernel->machine->WriteRegister(NextPCReg, kernel->machine->ReadRegister(PCReg)+4);
-			return;
-			ASSERTNOTREACHED();
-            break;
-      	case SC_Add:
-			DEBUG(dbgSys, "Add " << kernel->machine->ReadRegister(4) << " + " << kernel->machine->ReadRegister(5) << "\n");
-			/* Process SysAdd Systemcall*/
-			int result;
-			result = SysAdd(/* int op1 */(int)kernel->machine->ReadRegister(4),
-			/* int op2 */(int)kernel->machine->ReadRegister(5));
-			DEBUG(dbgSys, "Add returning with " << result << "\n");
-			/* Prepare Result */
-			kernel->machine->WriteRegister(2, (int)result);	
-			/* Modify return point */
-			{
-	  		/* set previous programm counter (debugging only)*/
-	  		kernel->machine->WriteRegister(PrevPCReg, kernel->machine->ReadRegister(PCReg));
-	  			
-			/* set programm counter to next instruction (all Instructions are 4 byte wide)*/
-	  		kernel->machine->WriteRegister(PCReg, kernel->machine->ReadRegister(PCReg) + 4);
-	  
-	 		/* set next programm counter for brach execution */
-	 		kernel->machine->WriteRegister(NextPCReg, kernel->machine->ReadRegister(PCReg)+4);
-			}
-			cout << "result is " << result << "\n";	
-			return;	
-			ASSERTNOTREACHED();
-            break;
-		case SC_Exit:
-			DEBUG(dbgAddr, "Program exit\n");
-            val=kernel->machine->ReadRegister(4);
-            cout << "return value:" << val << endl;
-			kernel->currentThread->Finish();
-            break;
-      	default:
-			cerr << "Unexpected system call " << type << "\n";
-			break;
-		}
-		break;
-	default:
-		cerr << "Unexpected user mode exception " << (int)which << "\n";
-		break;
-    }
-    ASSERTNOTREACHED();
+      switch(type) {
+        case SC_Halt:
+  		    DEBUG(dbgSys, "Shutdown, initiated by user program.\n");
+  		    SysHalt();
+          cout<<"in exception\n";
+          ASSERTNOTREACHED();
+          break;
+  	    case SC_MSG:
+          DEBUG(dbgSys, "Message received.\n");
+          val = kernel->machine->ReadRegister(4);
+          {
+            char *msg = &(kernel->machine->mainMemory[val]);
+            cout << msg << endl;
+          }
+          SysHalt();
+          ASSERTNOTREACHED();
+          break;
+        case SC_Create:
+          val = kernel->machine->ReadRegister(4);
+          {
+            char *filename = &(kernel->machine->mainMemory[val]);
+            //cout << filename << endl;
+            status = SysCreate(filename);
+            kernel->machine->WriteRegister(2, (int) status);
+          }
+          kernel->machine->WriteRegister(PrevPCReg, kernel->machine->ReadRegister(PCReg));
+          kernel->machine->WriteRegister(PCReg, kernel->machine->ReadRegister(PCReg) + 4);
+          kernel->machine->WriteRegister(NextPCReg, kernel->machine->ReadRegister(PCReg) + 4);
+          return;
+          ASSERTNOTREACHED();
+          break;
+        case SC_Add:
+          DEBUG(dbgSys, "Add " << kernel->machine->ReadRegister(4) << " + " << kernel->machine->ReadRegister(5) << "\n");
+          /* Process SysAdd Systemcall*/
+          int result;
+          result = SysAdd(/* int op1 */(int)kernel->machine->ReadRegister(4),
+          /* int op2 */(int)kernel->machine->ReadRegister(5));
+          DEBUG(dbgSys, "Add returning with " << result << "\n");
+          /* Prepare Result */
+          kernel->machine->WriteRegister(2, (int)result);	
+          /* Modify return point */
+          {
+            /* set previous programm counter (debugging only)*/
+            kernel->machine->WriteRegister(PrevPCReg, kernel->machine->ReadRegister(PCReg));
+              
+            /* set programm counter to next instruction (all Instructions are 4 byte wide)*/
+            kernel->machine->WriteRegister(PCReg, kernel->machine->ReadRegister(PCReg) + 4);
+        
+            /* set next programm counter for brach execution */
+            kernel->machine->WriteRegister(NextPCReg, kernel->machine->ReadRegister(PCReg) + 4);
+          }
+          cout << "result is " << result << "\n";	
+          return;	
+          ASSERTNOTREACHED();
+          break;
+        case SC_Exit:
+          DEBUG(dbgAddr, "Program exit\n");
+          val = kernel->machine->ReadRegister(4);
+          cout << "return value:" << val << endl;
+          kernel->currentThread->Finish();
+          break;
+        case SC_PrintInt:
+          DEBUG(dbgAddr, "Printing int\n");
+          val = (int)kernel->machine->ReadRegister(4);
+          SysPrintInt(val);
+
+          kernel->machine->WriteRegister(PrevPCReg, kernel->machine->ReadRegister(PCReg));
+          kernel->machine->WriteRegister(PCReg, kernel->machine->ReadRegister(PCReg) + 4);
+          kernel->machine->WriteRegister(NextPCReg, kernel->machine->ReadRegister(PCReg) + 4);
+          
+          return;
+          ASSERTNOTREACHED();
+          break;
+        case SC_Open:
+          DEBUG(dbgAddr, "Open file\n");
+
+          {
+            val = kernel->machine->ReadRegister(4);
+            char *name = &(kernel->machine->mainMemory[val]);
+            OpenFileId ret = SysOpen(name);
+            kernel->machine->WriteRegister(2, ret);
+          }
+ 
+          kernel->machine->WriteRegister(PrevPCReg, kernel->machine->ReadRegister(PCReg));
+          kernel->machine->WriteRegister(PCReg, kernel->machine->ReadRegister(PCReg) + 4);
+          kernel->machine->WriteRegister(NextPCReg, kernel->machine->ReadRegister(PCReg) + 4);
+
+          return;
+          ASSERTNOTREACHED();
+          break;
+        case SC_Read:
+          DEBUG(dbgAddr, "Read file\n");
+
+          {
+            val = kernel->machine->ReadRegister(4);
+            char *buffer = &(kernel->machine->mainMemory[val]);
+            int size = kernel->machine->ReadRegister(5);
+            OpenFileId id = (OpenFileId)kernel->machine->ReadRegister(6);
+            int ret = SysRead(buffer, size, id);
+            kernel->machine->WriteRegister(2, ret);
+          }
+
+          kernel->machine->WriteRegister(PrevPCReg, kernel->machine->ReadRegister(PCReg));
+          kernel->machine->WriteRegister(PCReg, kernel->machine->ReadRegister(PCReg) + 4);
+          kernel->machine->WriteRegister(NextPCReg, kernel->machine->ReadRegister(PCReg) + 4);
+
+          return;
+          ASSERTNOTREACHED();
+          break;
+        case SC_Write:
+          DEBUG(dbgAddr, "Write file\n");
+
+          {
+            val = kernel->machine->ReadRegister(4);
+            char *buffer = &(kernel->machine->mainMemory[val]);
+            int size = kernel->machine->ReadRegister(5);
+            OpenFileId id = (OpenFileId)kernel->machine->ReadRegister(6);
+            // fprintf(stderr, "buffer: %p\n", buffer);
+            // cerr << "size: " << size << endl;
+            // cerr << "id: " << id << endl;
+            int ret = SysWrite(buffer, size, id);
+            kernel->machine->WriteRegister(2, ret);
+          }
+
+          kernel->machine->WriteRegister(PrevPCReg, kernel->machine->ReadRegister(PCReg));
+          kernel->machine->WriteRegister(PCReg, kernel->machine->ReadRegister(PCReg) + 4);
+          kernel->machine->WriteRegister(NextPCReg, kernel->machine->ReadRegister(PCReg) + 4);
+
+          return;
+          ASSERTNOTREACHED();
+          break;
+        case SC_Close:
+          DEBUG(dbgAddr, "Close file\n");
+
+          {
+            OpenFileId id = (OpenFileId)kernel->machine->ReadRegister(4);
+            int ret = SysClose(id);
+            kernel->machine->WriteRegister(2, ret);
+          }
+
+          kernel->machine->WriteRegister(PrevPCReg, kernel->machine->ReadRegister(PCReg));
+          kernel->machine->WriteRegister(PCReg, kernel->machine->ReadRegister(PCReg) + 4);
+          kernel->machine->WriteRegister(NextPCReg, kernel->machine->ReadRegister(PCReg) + 4);
+
+          return;
+          ASSERTNOTREACHED();
+          break;
+        default:
+          cerr << "Unexpected system call " << type << "\n";
+          break;
+  	  }
+  	  break;
+    default:
+      cerr << "Unexpected user mode exception " << (int)which << "\n";
+      break;
+  }
+  ASSERTNOTREACHED();
 }
 
diff --git a/code/userprog/ksyscall.h b/code/userprog/ksyscall.h
index c27fd41..bf1b9f3 100644
--- a/code/userprog/ksyscall.h
+++ b/code/userprog/ksyscall.h
@@ -1,38 +1,104 @@
-/**************************************************************
- *
- * userprog/ksyscall.h
- *
- * Kernel interface for systemcalls 
- *
- * by Marcus Voelp  (c) Universitaet Karlsruhe
- *
- **************************************************************/
-
-#ifndef __USERPROG_KSYSCALL_H__ 
-#define __USERPROG_KSYSCALL_H__ 
-
-#include "kernel.h"
-
-#include "synchconsole.h"
-
-
-void SysHalt()
-{
-  kernel->interrupt->Halt();
-}
-
-int SysAdd(int op1, int op2)
-{
-  return op1 + op2;
-}
-
-int SysCreate(char *filename)
-{
-	// return value
-	// 1: success
-	// 0: failed
-	return kernel->interrupt->CreateFile(filename);
-}
-
-
-#endif /* ! __USERPROG_KSYSCALL_H__ */
+/**************************************************************
+ *
+ * userprog/ksyscall.h
+ *
+ * Kernel interface for systemcalls 
+ *
+ * by Marcus Voelp  (c) Universitaet Karlsruhe
+ *
+ **************************************************************/
+
+#ifndef __USERPROG_KSYSCALL_H__ 
+#define __USERPROG_KSYSCALL_H__ 
+
+#define INT_BUF_LENGTH 13
+
+#include "kernel.h"
+
+#include "synchconsole.h"
+
+
+void SysHalt()
+{
+  kernel->interrupt->Halt();
+}
+
+int SysAdd(int op1, int op2)
+{
+  return op1 + op2;
+}
+
+int SysCreate(char *filename)
+{
+  // return value
+  // 1: success
+  // 0: failed
+  return kernel->interrupt->CreateFile(filename);
+}
+
+void SysPrintInt(int value) {
+  static char zero[2] = "0";
+
+  if (value == 0) {
+    kernel->synchConsoleOut->PutString(zero);
+    return;
+  }
+
+  char outputBuf[INT_BUF_LENGTH];
+  bool isNeg = false;
+  int curPos = INT_BUF_LENGTH;
+  outputBuf[--curPos] = '\0';
+  outputBuf[--curPos] = '\n';
+  
+  if (value < 0) {
+    isNeg = true;
+    value = -value;
+  }
+
+  while (value > 0) {
+    outputBuf[--curPos] = '0' + (value % 10);
+    value /= 10;
+  }
+
+  if (isNeg)
+    outputBuf[--curPos] = '-';
+
+  kernel->synchConsoleOut->PutString(&outputBuf[curPos]);
+}
+
+OpenFileId SysOpen(char *name) {
+  OpenFileId id = -1;
+  for (int i = 0; i < 20; i++)
+    if (kernel->fileSystem->fileDescriptorTable[i] == NULL) {
+      id = i;
+      kernel->fileSystem->fileDescriptorTable[i] 
+        = kernel->fileSystem->Open(name);
+      if (kernel->fileSystem->fileDescriptorTable[i] == NULL)
+        return -1;
+      break;
+    }
+  return id;
+}
+
+int SysWrite(char *buffer, int size, OpenFileId id) {
+  if (id < 0 || id >= 20 || kernel->fileSystem->fileDescriptorTable[id] == NULL)
+    return -1;
+  return kernel->fileSystem->fileDescriptorTable[id]->Write(buffer, size);
+}
+
+int SysRead(char *buffer, int size, OpenFileId id) {
+  if (id < 0 || id >= 20 || kernel->fileSystem->fileDescriptorTable[id] == NULL)
+    return -1;
+  return kernel->fileSystem->fileDescriptorTable[id]->Read(buffer, size);
+}
+
+int SysClose(OpenFileId id) {
+  if (id < 0 || id >= 20 || kernel->fileSystem->fileDescriptorTable[id] == NULL)
+    return 0;
+  delete kernel->fileSystem->fileDescriptorTable[id];
+  kernel->fileSystem->fileDescriptorTable[id] = NULL;
+  return 1;
+}
+
+
+#endif /* ! __USERPROG_KSYSCALL_H__ */
diff --git a/code/userprog/synchconsole.cc b/code/userprog/synchconsole.cc
index 346ffe6..b786d7f 100644
--- a/code/userprog/synchconsole.cc
+++ b/code/userprog/synchconsole.cc
@@ -106,6 +106,15 @@ SynchConsoleOutput::PutChar(char ch)
     lock->Release();
 }
 
+void
+SynchConsoleOutput::PutString(char *str)
+{
+    lock->Acquire();
+    consoleOutput->PutString(str);
+    waitFor->P();
+    lock->Release();
+}
+
 //----------------------------------------------------------------------
 // SynchConsoleOutput::CallBack
 //      Interrupt handler called when it's safe to send the next 
diff --git a/code/userprog/synchconsole.h b/code/userprog/synchconsole.h
index b0f7a97..e412ff2 100644
--- a/code/userprog/synchconsole.h
+++ b/code/userprog/synchconsole.h
@@ -41,6 +41,7 @@ class SynchConsoleOutput : public CallBackObj {
     ~SynchConsoleOutput();
 
     void PutChar(char ch);	// Write a character, waiting if necessary
+    void PutString(char *ch);
    
   private:
     ConsoleOutput *consoleOutput;// the hardware display
diff --git a/code/userprog/syscall.h b/code/userprog/syscall.h
index 9fad2e3..ce6dd48 100644
--- a/code/userprog/syscall.h
+++ b/code/userprog/syscall.h
@@ -23,19 +23,22 @@
 #define SC_Exec		2
 #define SC_Join		3
 #define SC_Create	4
-#define SC_Remove       5
+#define SC_Remove 5
 #define SC_Open		6
 #define SC_Read		7
 #define SC_Write	8
-#define SC_Seek         9
-#define SC_Close	10
-#define SC_ThreadFork	11
+#define SC_Seek   9
+#define SC_Close	      10
+#define SC_ThreadFork	  11
 #define SC_ThreadYield	12
-#define SC_ExecV	13
+#define SC_ExecV        13
 #define SC_ThreadExit   14
 #define SC_ThreadJoin   15
-#define SC_Add		42
-#define SC_MSG		100
+
+#define SC_PrintInt     16
+
+#define SC_Add		      42
+#define SC_MSG	        100
 
 #ifndef IN_ASM
 
@@ -109,7 +112,7 @@ typedef int OpenFileId;
  */
 
 #define SysConsoleInput	0  
-#define SysConsoleOutput	1  
+#define SysConsoleOutput 1  
  
 /* Create a Nachos file, with name "name" */
 /* Note: Create does not open the file.   */
@@ -175,7 +178,9 @@ int ThreadJoin(ThreadId id);
 /*
  * Deletes current thread and returns ExitCode to every waiting lokal thread.
  */
-void ThreadExit(int ExitCode);	
+void ThreadExit(int ExitCode);
+
+void PrintInt(int number);
 
 #endif /* IN_ASM */
 
diff --git a/docker-compose.yaml b/docker-compose.yaml
new file mode 100644
index 0000000..06cced5
--- /dev/null
+++ b/docker-compose.yaml
@@ -0,0 +1,7 @@
+---
+services:
+  test:
+    build: .
+    user: '60139:60139'
+    volumes:
+      - './:/work'