diff --git a/.gitignore b/.gitignore
index 58e09e4..a60c662 100644
--- a/.gitignore
+++ b/.gitignore
@@ -3,3 +3,5 @@
 *.iml
 /*.txt
 /.vscode
+*.a
+*.o
diff --git a/test/Makefile b/Makefile
similarity index 64%
rename from test/Makefile
rename to Makefile
index 2cf5313..9daf3b6 100644
--- a/test/Makefile
+++ b/Makefile
@@ -7,24 +7,25 @@ all: dumps user_lib tests
 # Main targets
 #
 
-build: user_lib
-	$(MAKE) build -C riscv_instructions/
+instruction_tests:
+	$(MAKE) build -C test/riscv_instructions/
 
 dumps:
-	$(MAKE) dumps -C riscv_instructions/
+	$(MAKE) dumps -C test/riscv_instructions/
 	mkdir -p ${TOPDIR}/target/dumps/
 	find . -path ${TOPDIR}/target -prune -o -name '*.dump' -exec mv {} ${TOPDIR}/target/dumps/ \;
 
 user_lib:
 	$(MAKE) -C userlib/
+	mv ${TOPDIR}/userlib/sys.a ${TOPDIR}/src/sys.a
 
 tests: user_lib
-	$(MAKE) tests -C riscv_instructions/
+	$(MAKE) tests -C test/riscv_instructions/
 	mkdir -p ${TOPDIR}/target/guac/
 	find . -name '*.guac' -exec mv {} ${TOPDIR}/target/guac/ \;
 
 clean:
 	$(MAKE) clean -C userlib/
-	$(MAKE) clean -C riscv_instructions/
+	$(MAKE) clean -C test/riscv_instructions/
 	$(RM) -rf $(TOPDIR)/target
 	
\ No newline at end of file
diff --git a/test/Makefile.config b/Makefile.config
similarity index 100%
rename from test/Makefile.config
rename to Makefile.config
diff --git a/test/Makefile.tests b/Makefile.rules
similarity index 93%
rename from test/Makefile.tests
rename to Makefile.rules
index 14dba3d..58fab4b 100644
--- a/test/Makefile.tests
+++ b/Makefile.rules
@@ -18,6 +18,9 @@ CFLAGS  = $(RISCV_CFLAGS) $(INCPATH)
 %.o: %.c
 	$(GCC) $(CFLAGS) -c $<
 
+%.a: %.o
+	$(AR) $(ARFLAGS) $@ $<
+
 %.dump: %.o
 	$(RISCV_OBJCOPY) -j .text -O $(DUMP_FORMAT) $< $@
 
diff --git a/Makefile.userlib b/Makefile.userlib
new file mode 100644
index 0000000..e69de29
diff --git a/build.rs b/build.rs
index 7b5ec8a..ea3850b 100644
--- a/build.rs
+++ b/build.rs
@@ -1,5 +1,2 @@
 fn main() {
-    cc::Build::new()
-        .file("test/userlib/sys.s")
-        .compile("my-asm-lib");
 }
\ No newline at end of file
diff --git a/test/userlib/syscall.rs b/src/kernel/syscall.rs
similarity index 86%
rename from test/userlib/syscall.rs
rename to src/kernel/syscall.rs
index 54b82ba..14ceeb7 100644
--- a/test/userlib/syscall.rs
+++ b/src/kernel/syscall.rs
@@ -36,7 +36,8 @@ pub struct LockId{
 pub struct CondId{
     id: u64
 }
-extern "C"{
+
+extern "C" {
 
     ///Stop Nachos, and print out performance stats
     fn Shutdown() -> ();
@@ -49,11 +50,11 @@ extern "C"{
 
     /// Run the executable, stored in the Nachos file "name", and return the
     ///  master thread identifier
-    fn Exec(name: *char) -> ThreadId;
+    fn Exec(name: *const char) -> ThreadId;
 
     /// Create a new thread in the current process
     ///  Return thread identifier
-    fn newThread(debug_name: *char, func: i32, arg: i32) -> ThreadId;
+    fn newThread(debug_name: *const char, func: i32, arg: i32) -> ThreadId;
 
     /// Only return once the the thread "id" has finished.
     fn Join (id: ThreadId) -> t_error;
@@ -63,24 +64,24 @@ extern "C"{
     fn Yield() -> ();
 
     /// Print the last error message with the personalized one "mess"
-    fn PError(mess: *char) -> ();
+    fn PError(mess: *const char) -> ();
 
     /// Create a BurritOS file, with "name"
-    fn Create(name: *char, size: i32) -> t_error;
+    fn Create(name: *const char, size: i32) -> t_error;
 
     /// Open the Nachos file "name", and return an "OpenFileId" that can
     ///  be used to read and write to the file.
-    fn Open(name: *char) -> OpenFiledId;
+    fn Open(name: *const char) -> OpenFiledId;
 
     /// Write "size" bytes from "buffer" to the open file.
-    fn Write(buffer: *char, size: i32, id: OpenFiledId) -> t_error;
+    fn Write(buffer: *const char, size: i32, id: OpenFiledId) -> t_error;
 
     /// Read "size" bytes from the open file into "buffer".
     ///  Return the number of bytes actually read -- if the open file isn't
     ///  long enough, or if it is an I/O device, and there aren't enough
     ///  characters to read, return whatever is available (for I/O devices,
     ///  you should always wait until you can return at least one character).
-    fn Read(buffer: *char, size: i32, id:OpenFiledId) -> t_error;
+    fn Read(buffer: *const char, size: i32, id:OpenFiledId) -> t_error;
 
     /// Seek to a specified offset into an opened file
     fn Seek(offset: i32, id: OpenFiledId) -> t_error;
@@ -89,7 +90,7 @@ extern "C"{
     fn Close(id: OpenFiledId) -> t_error;
 
     /// Remove the file
-    fn Remove(name: *char) -> t_error;
+    fn Remove(name: *const char) -> t_error;
 
     ////////////////////////////////////////////////////
     /// system calls concerning directory management ///
@@ -97,11 +98,11 @@ extern "C"{
 
     /// Create a new repertory
     /// Return a negative number if an error ocurred.
-    fn mkdir(name: *char) -> t_length;
+    fn mkdir(name: *const char) -> t_length;
 
     /// Destroy a repertory, which must be empty.
     /// Return a negative number if an error ocurred.
-    fn Rmdir(name: *char) -> t_error;
+    fn Rmdir(name: *const char) -> t_error;
 
     /// List the content of BurritOS FileSystem
     fn FSList() -> t_error;
@@ -109,7 +110,7 @@ extern "C"{
     /// Create a semaphore, initialising it at count.
     /// Return a Semid, which will enable to do operations on this
     /// semaphore
-    fn SemCreate(debug_name: *char, count: i32) -> SemId;
+    fn SemCreate(debug_name: *const char, count: i32) -> SemId;
 
     /// Destroy a semaphore identified by sema.
     /// Return a negative number if an error occured during the destruction
@@ -123,7 +124,7 @@ extern "C"{
 
     /// Create a lock.
     /// Return an identifier
-    fn LockCreate(debug_name: *char) -> LockId;
+    fn LockCreate(debug_name: *const char) -> LockId;
 
     /// Destroy a lock.
     /// Return a negative number if an error ocurred
@@ -139,7 +140,7 @@ extern "C"{
     fn LockRelease(id: LockId) -> t_error;
 
     /// Create a new condition variable
-    fn CondCreate(debug_name: *char) -> CondId;
+    fn CondCreate(debug_name: *const char) -> CondId;
 
     /// Destroy a condition variable.
     /// Return a negative number if an error ocurred.
@@ -163,12 +164,12 @@ extern "C"{
 
     ///Send the message on the serial communication link.
     /// Returns the number of bytes successfully sent.
-    fn TtySend(mess: *char) -> i32;
+    fn TtySend(mess: *const char) -> i32;
 
     /// Wait for a message comming from the serial communication link.
     /// The length of the buffer where the bytes will be copied is given as a parameter.
     /// Returns the number of characters actually received.
-    fn TtyReceive(mess: *char, length: i32) -> i32;
+    fn TtyReceive(mess: *const char, length: i32) -> i32;
 
     /// Map an opened file in memory. Size is the size to be mapped in bytes.
     fn Mmap(id: OpenFiledId, size: i32) -> *mut ();
diff --git a/test/riscv_instructions/boolean_logic/Makefile b/test/riscv_instructions/boolean_logic/Makefile
index e9b0a52..b0d2554 100644
--- a/test/riscv_instructions/boolean_logic/Makefile
+++ b/test/riscv_instructions/boolean_logic/Makefile
@@ -7,8 +7,8 @@ dumps: comparisons.dump if.dump switch.dump
 
 tests: comparisons.guac if.guac switch.guac
 
-TOPDIR = ../..
-include $(TOPDIR)/Makefile.tests
+TOPDIR = ../../..
+include $(TOPDIR)/Makefile.rules
 
 clean:
 	$(RM) comparisons comparisons.o if if.o
diff --git a/test/riscv_instructions/jump_instructions/Makefile b/test/riscv_instructions/jump_instructions/Makefile
index 71ce3c0..72523a3 100644
--- a/test/riscv_instructions/jump_instructions/Makefile
+++ b/test/riscv_instructions/jump_instructions/Makefile
@@ -9,7 +9,7 @@ tests: jump.guac ret.guac
 clean:
 	$(RM) jump jump.o ret ret.o
 
-TOPDIR = ../..
-include $(TOPDIR)/Makefile.tests
+TOPDIR = ../../..
+include $(TOPDIR)/Makefile.rules
 
 $(PROGRAMS): % : $(USERLIB)/sys.o $(USERLIB)/libnachos.o %.o
\ No newline at end of file
diff --git a/test/riscv_instructions/simple_arithmetics/Makefile b/test/riscv_instructions/simple_arithmetics/Makefile
index 9b42a4b..1d3dcf2 100644
--- a/test/riscv_instructions/simple_arithmetics/Makefile
+++ b/test/riscv_instructions/simple_arithmetics/Makefile
@@ -10,7 +10,7 @@ tests: unsigned_addition.guac unsigned_division.guac unsigned_multiplication.gua
 clean:
 	$(RM) unsigned_addition unsigned_addition.o unsigned_division unsigned_division.o unsigned_multiplication unsigned_multiplication.o unsigned_substraction unsigned_substraction.o
 
-TOPDIR = ../..
-include $(TOPDIR)/Makefile.tests
+TOPDIR = ../../..
+include $(TOPDIR)/Makefile.rules
 
 $(PROGRAMS): % : $(USERLIB)/sys.o $(USERLIB)/libnachos.o %.o
\ No newline at end of file
diff --git a/test/riscv_instructions/syscall_tests/Makefile b/test/riscv_instructions/syscall_tests/Makefile
index 62b3741..e528387 100644
--- a/test/riscv_instructions/syscall_tests/Makefile
+++ b/test/riscv_instructions/syscall_tests/Makefile
@@ -10,7 +10,7 @@ tests: halt.guac prints.guac
 clean:
 	$(RM) halt.o halt prints prints.o 
 
-TOPDIR = ../..
-include $(TOPDIR)/Makefile.tests
+TOPDIR = ../../..
+include $(TOPDIR)/Makefile.rules
 
 $(PROGRAMS): % : $(USERLIB)/sys.o $(USERLIB)/libnachos.o %.o
\ No newline at end of file
diff --git a/test/userlib/Makefile b/test/userlib/Makefile
deleted file mode 100644
index 6a5c70f..0000000
--- a/test/userlib/Makefile
+++ /dev/null
@@ -1,7 +0,0 @@
-TOPDIR = ../
-include $(TOPDIR)/Makefile.tests
-
-default: sys.o libnachos.o
-
-clean:
-	$(RM) libnachos.o sys.o
\ No newline at end of file
diff --git a/userlib/Makefile b/userlib/Makefile
new file mode 100644
index 0000000..79d7bd9
--- /dev/null
+++ b/userlib/Makefile
@@ -0,0 +1,7 @@
+TOPDIR = ../
+include $(TOPDIR)/Makefile.rules
+
+default: sys.a libnachos.a
+
+clean:
+	$(RM) libnachos.a sys.a libnachos.o sys.o
\ No newline at end of file
diff --git a/test/userlib/ldscript.lds b/userlib/ldscript.lds
similarity index 100%
rename from test/userlib/ldscript.lds
rename to userlib/ldscript.lds
diff --git a/test/userlib/libnachos.c b/userlib/libnachos.c
similarity index 100%
rename from test/userlib/libnachos.c
rename to userlib/libnachos.c
diff --git a/test/userlib/libnachos.h b/userlib/libnachos.h
similarity index 100%
rename from test/userlib/libnachos.h
rename to userlib/libnachos.h
diff --git a/test/userlib/sys.s b/userlib/sys.s
similarity index 100%
rename from test/userlib/sys.s
rename to userlib/sys.s
diff --git a/test/userlib/syscall.h b/userlib/syscall.h
similarity index 100%
rename from test/userlib/syscall.h
rename to userlib/syscall.h