diff --git a/MString.cpp b/MString.cpp
index 4b48dd5..d645ccd 100644
--- a/MString.cpp
+++ b/MString.cpp
@@ -38,12 +38,18 @@ namespace coreutils {
       cursor = this->data;
    }
 
-   MString::MString(ZString zstring) {
+   MString::MString(const ZString &zstring) {
       setSize(zstring.getLength());
       memcpy(data, zstring.getData(), zstring.getLength());
       cursor = data;      
    }   
-   
+
+   MString::MString(ZString &zstring) {
+      setSize(zstring.getLength());
+      memcpy(data, zstring.getData(), zstring.getLength());
+      cursor = data;
+   }
+  
    MString::MString(const MString &mstring) {
       setSize(mstring.length);
       memcpy(data, mstring.data, mstring.length);
diff --git a/MString.h b/MString.h
index 7413744..70b8cdb 100644
--- a/MString.h
+++ b/MString.h
@@ -6,8 +6,7 @@
 #include <sstream>
 #include <ostream>
 
-namespace coreutils
-{
+namespace coreutils {
    
    ///
    /// Use the MString object when you need a permanent backing store on the heap
@@ -42,12 +41,15 @@ namespace coreutils
       
       MString(const unsigned char *data, size_t length);
 
-      MString (ZString zstring);
+//      MString (ZString zstring);
       
       ///
       /// Consructor providing a copy of a ZString.
       ///
       
+      MString (ZString &zstring);
+      MString (const ZString &zstring);
+
       ///
       /// Consructor providing a copy of a ZString.
       ///
diff --git a/ZString.cpp b/ZString.cpp
index 355b87f..c17c812 100644
--- a/ZString.cpp
+++ b/ZString.cpp
@@ -68,6 +68,8 @@ namespace coreutils {
    }
 
    bool ZString::operator==(const ZString &valuex) {
+      if((valuex.getLength() == 0) && (length != 0))
+	return false;
       return (strncmp(data, valuex.data, valuex.length <= length ? valuex.length : length) == 0);
    }
 
@@ -348,11 +350,11 @@ namespace coreutils {
       return ZString(temp, size);
    }
    
-   char *ZString::getData() {
+   char *ZString::getData() const {
       return data;
    }
    
-   char *ZString::getCursor() {
+   char *ZString::getCursor() const {
       return cursor;
    }
 
@@ -362,7 +364,7 @@ namespace coreutils {
       this->cursor = cursor;
    }
    
-   size_t ZString::getLength() {
+   size_t ZString::getLength() const {
       return length - (cursor - data);
    }
    
diff --git a/ZString.h b/ZString.h
index 62abfa5..830674f 100644
--- a/ZString.h
+++ b/ZString.h
@@ -311,13 +311,13 @@ namespace coreutils {
       /// the number of bytes specified by size.
       ///
       
-      char *getData();
+      char *getData() const;
       
       ///
       ///
       ///
       
-      char *getCursor();
+      char *getCursor() const;
       
       ///
       ///
@@ -329,7 +329,7 @@ namespace coreutils {
       /// Return the length of the ZString.
       ///
       
-      size_t getLength();
+      size_t getLength() const;
       
       ///
       /// Set this ZString to have the same data space as the ZString pointer
diff --git a/testing/compile b/testing/compile
index af391cf..12cdd09 100755
--- a/testing/compile
+++ b/testing/compile
@@ -1,4 +1,4 @@
 #!/bin/bash
-g++ -o zstring_test zstring_test.cpp -I.. -L.. -lCoreUtils
-g++ -o mstring_test mstring_test.cpp -I.. -L.. -lCoreUtils
+g++ -g -o zstring_test zstring_test.cpp -I.. -L.. -lCoreUtils
+g++ -g -o mstring_test mstring_test.cpp -I.. -L.. -lCoreUtils
 #g++ -o jstring_test jstring_test.cpp -I.. -L.. -lCoreUtils
diff --git a/testing/mstring_test b/testing/mstring_test
index 4a1eda2..abdf6a1 100755
Binary files a/testing/mstring_test and b/testing/mstring_test differ
diff --git a/testing/zstring_test b/testing/zstring_test
index 7d95339..065d9ae 100755
Binary files a/testing/zstring_test and b/testing/zstring_test differ
diff --git a/testing/zstring_test.cpp b/testing/zstring_test.cpp
index 56ac33a..c075315 100644
--- a/testing/zstring_test.cpp
+++ b/testing/zstring_test.cpp
@@ -6,8 +6,9 @@ int main(int argc, char **argv) {
 
    // Test comparison operations.
 
-   coreutils::ZString test1("");
+   coreutils::ZString test1("else");
    std::cout << (test1 != ".") << std::endl;
+   std::cout << (test1 == "") << std::endl;
 
    // Test constructors.