diff --git a/examples/hello_world/LoadShaders.h b/examples/hello_world/LoadShaders.h
index e8fd9a1c1..a5da4474c 100644
--- a/examples/hello_world/LoadShaders.h
+++ b/examples/hello_world/LoadShaders.h
@@ -77,7 +77,7 @@ inline GLuint LoadShaders()
 	// Compile Vertex Shader
 	std::cout << "Compiling vertex shader" << std::endl;
 	char const * VertexSourcePointer = VertexShaderCode.c_str();
-	glShaderSource(VertexShaderID, 1, &VertexSourcePointer, NULL);
+	glShaderSource(VertexShaderID, 1, &VertexSourcePointer, nullptr);
 	glCompileShader(VertexShaderID);
 
 	// Check Vertex Shader
@@ -86,14 +86,14 @@ inline GLuint LoadShaders()
 	std::vector<char> VertexShaderErrorMessage( static_cast<std::size_t>(InfoLogLength) );
 	if(VertexShaderErrorMessage.size() > 0)
 	{
-		glGetShaderInfoLog(VertexShaderID, InfoLogLength, NULL, &VertexShaderErrorMessage[0]);
+		glGetShaderInfoLog(VertexShaderID, InfoLogLength, nullptr, &VertexShaderErrorMessage[0]);
 		std::cout << &VertexShaderErrorMessage[0] << std::endl;
 	}
 
 	// Compile Fragment Shader
 	std::cout << "Compiling fragment shader" << std::endl;
 	char const * FragmentSourcePointer = FragmentShaderCode.c_str();
-	glShaderSource(FragmentShaderID, 1, &FragmentSourcePointer, NULL);
+	glShaderSource(FragmentShaderID, 1, &FragmentSourcePointer, nullptr);
 	glCompileShader(FragmentShaderID);
 
 	// Check Fragment Shader
@@ -102,7 +102,7 @@ inline GLuint LoadShaders()
 	std::vector<char> FragmentShaderErrorMessage( static_cast<std::size_t>(InfoLogLength) );
 	if(FragmentShaderErrorMessage.size() > 0)
 	{
-		glGetShaderInfoLog(FragmentShaderID, InfoLogLength, NULL, &FragmentShaderErrorMessage[0]);
+		glGetShaderInfoLog(FragmentShaderID, InfoLogLength, nullptr, &FragmentShaderErrorMessage[0]);
 		std::cout << &FragmentShaderErrorMessage[0] << std::endl;
 	}
 
@@ -119,7 +119,7 @@ inline GLuint LoadShaders()
 	std::vector<char> ProgramErrorMessage( static_cast<std::size_t>(InfoLogLength) );
 	if(ProgramErrorMessage.size() > 0)
 	{
-		glGetProgramInfoLog(ProgramID, InfoLogLength, NULL, &ProgramErrorMessage[0]);
+		glGetProgramInfoLog(ProgramID, InfoLogLength, nullptr, &ProgramErrorMessage[0]);
 		std::cout << &ProgramErrorMessage[0] << std::endl;
 	}
 
diff --git a/vtkm/Types.h b/vtkm/Types.h
index 9190a05e6..24957e339 100644
--- a/vtkm/Types.h
+++ b/vtkm/Types.h
@@ -1062,7 +1062,7 @@ public:
 
   VTKM_EXEC_CONT
   VecC()
-    : Components(NULL), NumberOfComponents(0)
+    : Components(nullptr), NumberOfComponents(0)
   {  }
 
   VTKM_EXEC_CONT
@@ -1151,7 +1151,7 @@ public:
 
   VTKM_EXEC_CONT
   VecCConst()
-    : Components(NULL), NumberOfComponents(0)
+    : Components(nullptr), NumberOfComponents(0)
   {  }
 
   VTKM_EXEC_CONT
diff --git a/vtkm/cont/tbb/internal/parallel_sort.h b/vtkm/cont/tbb/internal/parallel_sort.h
index f45616b19..3412a58c3 100644
--- a/vtkm/cont/tbb/internal/parallel_sort.h
+++ b/vtkm/cont/tbb/internal/parallel_sort.h
@@ -86,14 +86,14 @@ public:
         size_t j=range.size;
         // Partition interval [i+1,j-1] with key *key0.
         for(;;) {
-            __TBB_ASSERT( i<j, NULL );
+            __TBB_ASSERT( i<j, nullptr );
             // Loop must terminate since array[l]==*key0.
             do {
                 --j;
                 __TBB_ASSERT( i<=j, "bad ordering relation?" );
             } while( comp( *key0, array[j] ));
             do {
-                __TBB_ASSERT( i<=j, NULL );
+                __TBB_ASSERT( i<=j, nullptr );
                 if( i==j ) goto partition;
                 ++i;
             } while( comp( array[i],*key0 ));
diff --git a/vtkm/cont/testing/UnitTestDataSetBuilderUniform.cxx b/vtkm/cont/testing/UnitTestDataSetBuilderUniform.cxx
index 58f6f5f5c..3d7d56da5 100644
--- a/vtkm/cont/testing/UnitTestDataSetBuilderUniform.cxx
+++ b/vtkm/cont/testing/UnitTestDataSetBuilderUniform.cxx
@@ -245,7 +245,7 @@ UniformTests()
 void
 TestDataSetBuilderUniform()
 {
-  vtkm::UInt32 seed = static_cast<vtkm::UInt32>(time(NULL));
+  vtkm::UInt32 seed = static_cast<vtkm::UInt32>(time(nullptr));
   std::cout << "Seed: " << seed << std::endl;
   g_RandomGenerator.seed(seed);
 
diff --git a/vtkm/exec/AtomicArray.h b/vtkm/exec/AtomicArray.h
index b5ba204ba..1ade7b20a 100644
--- a/vtkm/exec/AtomicArray.h
+++ b/vtkm/exec/AtomicArray.h
@@ -54,7 +54,7 @@ public:
 
   VTKM_CONT
   AtomicArray()
-    : AtomicImplementation(vtkm::cont::make_ArrayHandle((T*)NULL, 0))
+    : AtomicImplementation(vtkm::cont::make_ArrayHandle((T*)nullptr, 0))
   {  }
 
   template<typename StorageType>
diff --git a/vtkm/exec/internal/ErrorMessageBuffer.h b/vtkm/exec/internal/ErrorMessageBuffer.h
index 9802a5bab..b814f8d45 100644
--- a/vtkm/exec/internal/ErrorMessageBuffer.h
+++ b/vtkm/exec/internal/ErrorMessageBuffer.h
@@ -41,7 +41,7 @@ class ErrorMessageBuffer
 {
 public:
   VTKM_EXEC_CONT ErrorMessageBuffer()
-    : MessageBuffer(NULL), MessageBufferSize(0) {  }
+    : MessageBuffer(nullptr), MessageBufferSize(0) {  }
 
   VTKM_EXEC_CONT
   ErrorMessageBuffer(char *messageBuffer, vtkm::Id bufferSize)
diff --git a/vtkm/exec/internal/testing/UnitTestWorkletInvokeFunctor.cxx b/vtkm/exec/internal/testing/UnitTestWorkletInvokeFunctor.cxx
index 928a8522f..0bbe30e06 100644
--- a/vtkm/exec/internal/testing/UnitTestWorkletInvokeFunctor.cxx
+++ b/vtkm/exec/internal/testing/UnitTestWorkletInvokeFunctor.cxx
@@ -36,7 +36,7 @@ namespace {
 struct TestExecObject
 {
   VTKM_EXEC_CONT
-  TestExecObject() : Value(NULL) {  }
+  TestExecObject() : Value(nullptr) {  }
 
   VTKM_EXEC_CONT
   TestExecObject(vtkm::Id *value) : Value(value) {  }
diff --git a/vtkm/exec/testing/UnitTestCellDerivative.cxx b/vtkm/exec/testing/UnitTestCellDerivative.cxx
index bd21a4c56..257597200 100644
--- a/vtkm/exec/testing/UnitTestCellDerivative.cxx
+++ b/vtkm/exec/testing/UnitTestCellDerivative.cxx
@@ -316,7 +316,7 @@ struct TestDerivativeFunctor
 
 void TestDerivative()
 {
-  vtkm::UInt32 seed = static_cast<vtkm::UInt32>(std::time(NULL));
+  vtkm::UInt32 seed = static_cast<vtkm::UInt32>(std::time(nullptr));
   std::cout << "Seed: " << seed << std::endl;
   g_RandomGenerator.seed(seed);
 
diff --git a/vtkm/interop/BufferState.h b/vtkm/interop/BufferState.h
index 12e2abce0..65f344e7e 100644
--- a/vtkm/interop/BufferState.h
+++ b/vtkm/interop/BufferState.h
@@ -89,7 +89,7 @@ public:
   }
 
   BufferState():
-    OpenGLHandle(NULL),
+    OpenGLHandle(nullptr),
     BufferType(GL_INVALID_VALUE),
      SizeOfActiveSection(0),
      CapacityOfBuffer(0),
diff --git a/vtkm/rendering/CanvasEGL.cxx b/vtkm/rendering/CanvasEGL.cxx
index 7e379ef64..94d572670 100644
--- a/vtkm/rendering/CanvasEGL.cxx
+++ b/vtkm/rendering/CanvasEGL.cxx
@@ -102,7 +102,7 @@ void CanvasEGL::Initialize()
   }
   eglBindAPI(EGL_OPENGL_API);
   this->Internals->Context =
-      eglCreateContext(this->Internals->Display, cfg, EGL_NO_CONTEXT, NULL);
+      eglCreateContext(this->Internals->Display, cfg, EGL_NO_CONTEXT, nullptr);
   if (!this->Internals->Context)
   {
     throw vtkm::cont::ErrorBadValue("Failed to create EGL context");
diff --git a/vtkm/rendering/CanvasOSMesa.cxx b/vtkm/rendering/CanvasOSMesa.cxx
index 626c9dc43..e448c388e 100644
--- a/vtkm/rendering/CanvasOSMesa.cxx
+++ b/vtkm/rendering/CanvasOSMesa.cxx
@@ -64,7 +64,7 @@ CanvasOSMesa::~CanvasOSMesa()
 void CanvasOSMesa::Initialize()
 {
   this->Internals->Context =
-      OSMesaCreateContextExt(OSMESA_RGBA, 32, 0, 0, NULL);
+      OSMesaCreateContextExt(OSMESA_RGBA, 32, 0, 0, nullptr);
 
   if (!this->Internals->Context)
   {
diff --git a/vtkm/rendering/MapperGL.cxx b/vtkm/rendering/MapperGL.cxx
index e919b875d..8411465fb 100644
--- a/vtkm/rendering/MapperGL.cxx
+++ b/vtkm/rendering/MapperGL.cxx
@@ -270,9 +270,9 @@ void RenderTriangles(MapperGL &mapper,
     glGenVertexArrays(1, &mapper.vao);
     glBindVertexArray(mapper.vao);
     glBindBuffer(GL_ARRAY_BUFFER, points_vbo);
-    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, NULL);
+    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, nullptr);
     glBindBuffer(GL_ARRAY_BUFFER, colours_vbo);
-    glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 0, NULL);
+    glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 0, nullptr);
 
     glEnableVertexAttribArray(0);
     glEnableVertexAttribArray(1);
@@ -297,7 +297,7 @@ void RenderTriangles(MapperGL &mapper,
         "}";
 
     GLuint vs = glCreateShader(GL_VERTEX_SHADER);
-    glShaderSource(vs, 1, &vertex_shader, NULL);
+    glShaderSource(vs, 1, &vertex_shader, nullptr);
     glCompileShader(vs);
     GLint isCompiled = 0;
     glGetShaderiv(vs, GL_COMPILE_STATUS, &isCompiled);
@@ -311,7 +311,7 @@ void RenderTriangles(MapperGL &mapper,
         msg = "No error message";
       else
       {
-        // The maxLength includes the NULL character
+        // The maxLength includes the nullptr character
         GLchar *strInfoLog = new GLchar[maxLength + 1];
         glGetShaderInfoLog(vs, maxLength, &maxLength, strInfoLog);
         msg = std::string(strInfoLog);
@@ -321,7 +321,7 @@ void RenderTriangles(MapperGL &mapper,
     }
 
     GLuint fs = glCreateShader(GL_FRAGMENT_SHADER);
-    glShaderSource(fs, 1, &fragment_shader, NULL);
+    glShaderSource(fs, 1, &fragment_shader, nullptr);
     glCompileShader(fs);
     glGetShaderiv(fs, GL_COMPILE_STATUS, &isCompiled);
     if(isCompiled == GL_FALSE)
@@ -334,7 +334,7 @@ void RenderTriangles(MapperGL &mapper,
           msg = "No error message";
       else
       {
-        // The maxLength includes the NULL character
+        // The maxLength includes the nullptr character
         GLchar *strInfoLog = new GLchar[maxLength + 1];
         glGetShaderInfoLog(vs, maxLength, &maxLength, strInfoLog);
         msg = std::string(strInfoLog);
@@ -388,7 +388,7 @@ void RenderTriangles(MapperGL &mapper,
 
 } // anonymous namespace
 
-MapperGL::MapperGL() : Canvas(NULL), loaded(false)
+MapperGL::MapperGL() : Canvas(nullptr), loaded(false)
 {
 }
 
@@ -474,10 +474,10 @@ void MapperGL::EndScene()
 
 void MapperGL::SetCanvas(vtkm::rendering::Canvas *c)
 {
-  if (c != NULL)
+  if (c != nullptr)
   {
     this->Canvas = dynamic_cast<vtkm::rendering::CanvasGL*>(c);
-    if (this->Canvas == NULL)
+    if (this->Canvas == nullptr)
       throw vtkm::cont::ErrorBadValue("Bad canvas type for MapperGL. Must be CanvasGL");
   }
 }
diff --git a/vtkm/rendering/MapperRayTracer.cxx b/vtkm/rendering/MapperRayTracer.cxx
index bd41c1c8a..5e16d485c 100644
--- a/vtkm/rendering/MapperRayTracer.cxx
+++ b/vtkm/rendering/MapperRayTracer.cxx
@@ -51,7 +51,7 @@ struct MapperRayTracer::InternalsType
     typedef vtkm::rendering::raytracing::RayTracer<Device> RayTracerType;
     typedef vtkm::cont::internal::SimplePolymorphicContainer<RayTracerType>
         ContainerType;
-    RayTracerType *tracer = NULL;
+    RayTracerType *tracer = nullptr;
     if (this->RayTracerContainer)
     {
       ContainerType *container =
@@ -62,7 +62,7 @@ struct MapperRayTracer::InternalsType
       }
     }
 
-    if (tracer == NULL)
+    if (tracer == nullptr)
     {
       ContainerType *container
           = new vtkm::cont::internal::SimplePolymorphicContainer<RayTracerType>;
diff --git a/vtkm/rendering/MapperVolume.cxx b/vtkm/rendering/MapperVolume.cxx
index 9692af0d7..be9194564 100644
--- a/vtkm/rendering/MapperVolume.cxx
+++ b/vtkm/rendering/MapperVolume.cxx
@@ -65,7 +65,7 @@ struct MapperVolume::InternalsType
         RayTracerType;
     typedef vtkm::cont::internal::SimplePolymorphicContainer<RayTracerType>
         ContainerType;
-    RayTracerType *tracer = NULL;
+    RayTracerType *tracer = nullptr;
     if (this->RayTracerContainer)
     {
       ContainerType *container =
@@ -76,7 +76,7 @@ struct MapperVolume::InternalsType
       }
     }
 
-    if (tracer == NULL)
+    if (tracer == nullptr)
     {
       ContainerType *container
           = new vtkm::cont::internal::SimplePolymorphicContainer<RayTracerType>;
@@ -156,8 +156,8 @@ struct MapperVolume::RenderFunctor
     if(this->Self->Internals->SampleDistance != DEFAULT_SAMPLE_DISTANCE)
     {
       tracer->SetSampleDistance(this->Self->Internals->SampleDistance);
-    } 
-      
+    }
+
     tracer->SetCompositeBackground(this->Self->Internals->CompositeBackground);
     vtkm::Bounds dataBounds = this->Coordinates.GetBounds();
 
diff --git a/vtkm/rendering/testing/glfw/UnitTestMapperGLFW.cxx b/vtkm/rendering/testing/glfw/UnitTestMapperGLFW.cxx
index cb413ed2f..72b5d34dc 100644
--- a/vtkm/rendering/testing/glfw/UnitTestMapperGLFW.cxx
+++ b/vtkm/rendering/testing/glfw/UnitTestMapperGLFW.cxx
@@ -47,7 +47,7 @@ keyCallback(GLFWwindow* vtkmNotUsed(window), int key,
       done = true;
   if (action == 1)
     which = (which+1) % NUM_DATASETS;
-}   
+}
 
 void RenderTests()
 {
@@ -57,12 +57,12 @@ void RenderTests()
     typedef vtkm::rendering::CanvasGL CanvasType;
     typedef vtkm::rendering::View3D View3DType;
     typedef vtkm::rendering::View2D View2DType;
-    
+
     vtkm::cont::testing::MakeTestDataSet maker;
     vtkm::rendering::ColorTable colorTable("thermal");
-    
+
     glfwInit();
-    GLFWwindow *window = glfwCreateWindow(WIDTH, HEIGHT, "GLFW Test", NULL, NULL);
+    GLFWwindow *window = glfwCreateWindow(WIDTH, HEIGHT, "GLFW Test", nullptr, nullptr);
     glfwMakeContextCurrent(window);
     glfwSetKeyCallback(window, keyCallback);
 
diff --git a/vtkm/rendering/testing/glut/UnitTestMapperGLUT.cxx b/vtkm/rendering/testing/glut/UnitTestMapperGLUT.cxx
index 15e7269f1..2cb216267 100644
--- a/vtkm/rendering/testing/glut/UnitTestMapperGLUT.cxx
+++ b/vtkm/rendering/testing/glut/UnitTestMapperGLUT.cxx
@@ -58,7 +58,7 @@ displayCall()
 {
   vtkm::cont::testing::MakeTestDataSet maker;
   vtkm::rendering::ColorTable colorTable("thermal");
-  
+
   typedef vtkm::rendering::MapperGL<VTKM_DEFAULT_DEVICE_ADAPTER_TAG> M;
   typedef vtkm::rendering::CanvasGL C;
   typedef vtkm::rendering::View3D V3;
@@ -94,7 +94,7 @@ void RenderTests()
     std::cout<<"Press any key to cycle through datasets. ESC to quit."<<std::endl;
 
   int argc = 0;
-  char *argv = NULL;
+  char *argv = nullptr;
   glutInit(&argc, &argv);
   glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
   glutInitWindowSize(WIDTH,HEIGHT);
@@ -103,10 +103,10 @@ void RenderTests()
   glutKeyboardFunc(keyboardCall);
   if (batch)
     glutIdleFunc(batchIdle);
-  
+
   glutMainLoop();
 }
-    
+
 } //namespace
 
 int UnitTestMapperGLUT(int argc, char *argv[])
@@ -117,6 +117,6 @@ int UnitTestMapperGLUT(int argc, char *argv[])
     {
       batch = true;
     }
-  }    
+  }
   return vtkm::cont::testing::Testing::Run(RenderTests);
 }
diff --git a/vtkm/testing/OptionParser.h b/vtkm/testing/OptionParser.h
index 06682080f..31d69fb5e 100644
--- a/vtkm/testing/OptionParser.h
+++ b/vtkm/testing/OptionParser.h
@@ -274,7 +274,7 @@ enum ArgStatus
  * @code ArgStatus CheckArg(const Option& option, bool msg); @endcode
  *
  * It is used to check if a potential argument would be acceptable for the option.
- * It will even be called if there is no argument. In that case @c option.arg will be @c NULL.
+ * It will even be called if there is no argument. In that case @c option.arg will be @c nullptr.
  *
  * If @c msg is @c true and the function determines that an argument is not acceptable and
  * that this is a fatal error, it should output a message to the user before
@@ -353,7 +353,7 @@ struct Descriptor
    * behaviour.
    *
    * If this Descriptor should not have short option characters, use the empty
-   * string "". NULL is not permitted here!
+   * string "". nullptr is not permitted here!
    *
    * See @ref longopt for more information.
    */
@@ -363,7 +363,7 @@ struct Descriptor
    * @brief The long option name (without the leading @c -- ).
    *
    * If this Descriptor should not have a long option name, use the empty
-   * string "". NULL is not permitted here!
+   * string "". nullptr is not permitted here!
    *
    * While @ref shortopt allows multiple short option characters, each
    * Descriptor can have only a single long option name. If you have multiple
@@ -399,7 +399,7 @@ struct Descriptor
    * will be called to check a potential argument to the option.
    *
    * This function will be called even if there is no potential argument. In that case
-   * it will be passed @c NULL as @c arg parameter. Do not confuse this with the empty
+   * it will be passed @c nullptr as @c arg parameter. Do not confuse this with the empty
    * string.
    *
    * See @ref CheckArg for more information.
@@ -453,7 +453,7 @@ public:
    * for unknown options.
    *
    * @attention
-   * @c desc==NULL signals that this Option is unused. This is the default state of
+   * @c desc==nullptr signals that this Option is unused. This is the default state of
    * elements in the result array. You don't need to test @c desc explicitly. You
    * can simply write something like this:
    * @code
@@ -485,7 +485,7 @@ public:
   /**
    * @brief Pointer to this Option's argument (if any).
    *
-   * NULL if this option has no argument. Do not confuse this with the empty string which
+   * nullptr if this option has no argument. Do not confuse this with the empty string which
    * is a valid argument.
    */
   const char* arg;
@@ -637,10 +637,10 @@ public:
   }
 
   /**
-   * @brief Returns a pointer to the previous element of the linked list or NULL if
+   * @brief Returns a pointer to the previous element of the linked list or nullptr if
    * called on first().
    *
-   * If called on first() this method returns NULL. Otherwise it will return the
+   * If called on first() this method returns nullptr. Otherwise it will return the
    * option with the same Descriptor::index that precedes this option on the command
    * line.
    */
@@ -663,10 +663,10 @@ public:
   }
 
   /**
-   * @brief Returns a pointer to the next element of the linked list or NULL if called
+   * @brief Returns a pointer to the next element of the linked list or nullptr if called
    * on last().
    *
-   * If called on last() this method returns NULL. Otherwise it will return the
+   * If called on last() this method returns nullptr. Otherwise it will return the
    * option with the same Descriptor::index that follows this option on the command
    * line.
    */
@@ -711,8 +711,8 @@ public:
   /**
    * @brief Casts from Option to const Option* but only if this Option is valid.
    *
-   * If this Option is valid (i.e. @c desc!=NULL), returns this.
-   * Otherwise returns NULL. This allows testing an Option directly
+   * If this Option is valid (i.e. @c desc!=nullptr), returns this.
+   * Otherwise returns nullptr. This allows testing an Option directly
    * in an if-clause to see if it is used:
    * @code
    * if (options[CREATE])
@@ -732,8 +732,8 @@ public:
   /**
    * @brief Casts from Option to Option* but only if this Option is valid.
    *
-   * If this Option is valid (i.e. @c desc!=NULL), returns this.
-   * Otherwise returns NULL. This allows testing an Option directly
+   * If this Option is valid (i.e. @c desc!=nullptr), returns this.
+   * Otherwise returns nullptr. This allows testing an Option directly
    * in an if-clause to see if it is used:
    * @code
    * if (options[CREATE])
@@ -751,7 +751,7 @@ public:
   }
 
   /**
-   * @brief Creates a new Option that is a one-element linked list and has NULL
+   * @brief Creates a new Option that is a one-element linked list and has nullptr
    * @ref desc, @ref name, @ref arg and @ref namelen.
    */
   Option() :
@@ -1110,10 +1110,10 @@ public:
    * @param usage Array of Descriptor objects that describe the options to support. The last entry
    *              of this array must have 0 in all fields.
    * @param argc The number of elements from @c argv that are to be parsed. If you pass -1, the number
-   *             will be determined automatically. In that case the @c argv list must end with a NULL
+   *             will be determined automatically. In that case the @c argv list must end with a nullptr
    *             pointer.
    * @param argv The arguments to be parsed. If you pass -1 as @c argc the last pointer in the @c argv
-   *             list must be NULL to mark the end.
+   *             list must be nullptr to mark the end.
    * @param options Each entry is the first element of a linked list of Options. Each new option
    *                that is parsed will be appended to the list specified by that Option's
    *                Descriptor::index. If an entry is not yet used (i.e. the Option is invalid),
@@ -1515,7 +1515,7 @@ inline void Stats::add(bool gnu, const Descriptor usage[], int argc, const char*
 inline bool Parser::workhorse(bool gnu, const Descriptor usage[], int numargs, const char** args, Action& action,
                               bool single_minus_longopt, bool print_errors, int min_abbr_len)
 {
-  // protect against NULL pointer
+  // protect against nullptr pointer
   if (args == 0)
   { numargs = 0; }
 
@@ -1896,8 +1896,8 @@ struct PrintUsageImplementation
    * iterates over these components.
    *
    * The top-level organizational unit is the @e table.
-   * A table begins at a Descriptor with @c help!=NULL and extends up to
-   * a Descriptor with @c help==NULL.
+   * A table begins at a Descriptor with @c help!=nullptr and extends up to
+   * a Descriptor with @c help==nullptr.
    *
    * A table consists of @e rows. Due to line-wrapping and explicit breaks
    * a row may take multiple lines on screen. Rows within the table are separated