diff --git a/code/machine/machine.h b/code/machine/machine.h
index 5422e22..f58b667 100644
--- a/code/machine/machine.h
+++ b/code/machine/machine.h
@@ -36,7 +36,7 @@
 					// the disk sector size, for
 					// simplicity
 
-#define NumPhysPages    64		// Increase this as necessary!
+#define NumPhysPages    128		// Increase this as necessary!
 #define MemorySize 	(NumPhysPages * PageSize)
 #define TLBSize		4		// if there is a TLB, make it small
 
diff --git a/code/test/start.S b/code/test/start.S
index d79b2f4..353097d 100644
--- a/code/test/start.S
+++ b/code/test/start.S
@@ -213,7 +213,15 @@ ThreadExit:
 	syscall
 	j	$31
 	.end ThreadExit
-    
+ 
+
+    .globl ForkExec
+    .ent   ForkExec
+ForkExec:
+    addiu $2,$0,SC_ForkExec
+	syscall
+	j	$31
+	.end ForkExec
 #endif
 
 /* dummy function to keep gcc happy */
diff --git a/code/test/userpages0 b/code/test/userpages0
index b624377..ce0fec1 100644
Binary files a/code/test/userpages0 and b/code/test/userpages0 differ
diff --git a/code/threads/system.h b/code/threads/system.h
index 2461e18..c0d2dda 100644
--- a/code/threads/system.h
+++ b/code/threads/system.h
@@ -34,7 +34,7 @@ extern Timer *timer;		// the hardware alarm clock
 extern Machine *machine;	// user program memory and registers
 
 #ifdef CHANGED
-#define MAX_STRING_SIZE 8
+#define MAX_STRING_SIZE 64
 #include "consoledriver.h"
 extern ConsoleDriver *consoledriver; // add console driver
 #include "pageprovider.h"
diff --git a/code/userprog/exception.cc b/code/userprog/exception.cc
index c8c0a83..88d244a 100644
--- a/code/userprog/exception.cc
+++ b/code/userprog/exception.cc
@@ -226,6 +226,14 @@ ExceptionHandler (ExceptionType which)
             do_ThreadExit();
             break;
           }
+        case SC_ForkExec:
+          {
+            int s = machine->ReadRegister(4);
+            char * command = new char[MAX_STRING_SIZE];
+            int size = copyStringFromMachine(s, command, MAX_STRING_SIZE);
+            do_ForkExec(command);
+            break;
+          }
         #endif
 		default:
 		  {
diff --git a/code/userprog/syscall.h b/code/userprog/syscall.h
index 94c598a..3b930b3 100644
--- a/code/userprog/syscall.h
+++ b/code/userprog/syscall.h
@@ -40,6 +40,7 @@
 #define SC_GetInt       16
 #define SC_ThreadCreate 17
 #define SC_ThreadExit   18
+#define SC_ForkExec     19
 #endif
 #ifdef IN_USER_MODE
 
@@ -148,6 +149,7 @@ void PutInt(int n);
 void GetInt( int * n);
 int ThreadCreate(void f(void * args), void * args);
 void ThreadExit(void);
+int ForkExec ( const char * s);
 
 #endif // CHANGED
 
diff --git a/code/userprog/userthread.cc b/code/userprog/userthread.cc
index 9267df8..f93039e 100644
--- a/code/userprog/userthread.cc
+++ b/code/userprog/userthread.cc
@@ -88,8 +88,46 @@ void do_ThreadExit(){
     if ( currentThread->space->threads == 0 ){
         // No threads remains, desallocate addrspace
         delete currentThread->space;
-        Exit(0);
+        currentThread->space = NULL;
     }
     currentThread->Finish();
 }
+
+void StartUserProc( void * args ){
+    currentThread->space->InitRegisters();
+    currentThread->space->RestoreState(); 
+    machine->DumpMem("memory.svg");
+    machine->Run();
+}
+
+int do_ForkExec( const char * c){
+    DEBUG('x', "Enter ForkExec\n");
+    AddrSpace * space;
+	Thread * fork;
+	OpenFile * file;            
+
+	file = fileSystem->Open(c);
+
+	if (file == NULL) {
+		printf("Unable to open file %s\n", file);	
+		return -1;
+	}
+		
+    try { 
+    	space = new AddrSpace(file);
+    }catch(const std::bad_alloc& e) {
+    	printf("==> BAD ALLOC ERROR: no empty space\n");
+    	delete space;
+    	ASSERT(false);
+    }
+    
+	fork = new Thread("forkThread");	
+	fork->space = space;
+	fork->Start(StartUserProc, NULL);
+
+	delete file;
+
+	return 0;
+}
+
 #endif
diff --git a/code/userprog/userthread.h b/code/userprog/userthread.h
index e49b51b..42028f8 100644
--- a/code/userprog/userthread.h
+++ b/code/userprog/userthread.h
@@ -11,4 +11,5 @@ typedef struct {
 
 extern int do_ThreadCreate(int f, int arg);
 extern void do_ThreadExit();
+extern int do_ForkExec( const char * s);
 #endif