diff --git a/imageInput.c b/imageInput.c
index 791a49b..3d06060 100644
--- a/imageInput.c
+++ b/imageInput.c
@@ -12,9 +12,11 @@ static void einzelBild(unsigned char *px_ls, FILE *file, GrayScaleImageSeries *s
     bild.height = hoehe;
     bild.width = breite;
     bild.buffer = malloc(sizeof(GrayScalePixelType)*hoehe*breite);
+    if(bild.buffer == NULL){
+        return;
+    }
 
     int anz = fread(px_ls,sizeof(unsigned char), hoehe*breite +1, file);
-    //printf("Test\n%d\n%d\n",anz, (breite*hoehe + 1));
 
     if(anz == (breite*hoehe + 1)){
         series->labels[bildnummer] = px_ls[breite*hoehe];
@@ -42,16 +44,29 @@ GrayScaleImageSeries *readImages(const char *path)
 
 
     ausgelesen = malloc(sizeof(char)*BUFFER_SIZE);
+
+    if(anzahl_ls == NULL || breite_ls == NULL ||hoehe_ls == NULL || ausgelesen == NULL){
+        return series;
+    }
+
     file = fopen(path,"rb");
     if(file==NULL){                                         //Fehlerbehandlung
         printf("Fehler bei File-Suche\n");
+        free(anzahl_ls);
+        free(breite_ls);
+        free(hoehe_ls);
+        free(ausgelesen);
         fclose(file);
         return series;
     }
-    fread(ausgelesen,sizeof(char), strlen(FILE_HEADER_STRING), file);
+    fread(ausgelesen,sizeof(unsigned char), strlen(FILE_HEADER_STRING), file);
 
-    if(strcmp(ausgelesen,FILE_HEADER_STRING)!=0){
+    if(memcmp(ausgelesen,FILE_HEADER_STRING,strlen(FILE_HEADER_STRING))!=0){
         printf("Kein richtiger File-Header vorhanden\n");
+        free(anzahl_ls);
+        free(breite_ls);
+        free(hoehe_ls);
+        free(ausgelesen);
         fclose(file);
         return series;
     }
@@ -64,16 +79,35 @@ GrayScaleImageSeries *readImages(const char *path)
                 breite = breite_ls[0];
                 hoehe = hoehe_ls[0];
                 series = malloc(sizeof(GrayScaleImageSeries)*(1+anzahl_ls[0]+anzahl_ls[0]*breite*hoehe));
+                if(series == NULL){
+                    return series;
+                }
                 series->count = anzahl_ls[0];
                 
-                //printf("%d\n%d\n%d\n",series->count, breite, hoehe);
                 series->images = malloc(sizeof(GrayScaleImage)*series->count);
                 series->labels = malloc(sizeof(unsigned char)*series->count);
+                if (series->images == NULL || series->labels == NULL){
+                    free(anzahl_ls);
+                    free(breite_ls);
+                    free(hoehe_ls);
+                    free(ausgelesen);
+                    fclose(file);
+                    return series;
+                }
             }
         }
     }
 
     px_ls = malloc(sizeof(GrayScalePixelType)*hoehe*breite +1);                         //Speicheranpassung für Einlese-Buffer
+    if(px_ls == NULL){
+        free(anzahl_ls);
+        free(breite_ls);
+        free(hoehe_ls);
+        free(px_ls);
+        free(ausgelesen);
+        fclose(file);
+        return series;
+    }
 
     for(int bildnummer=0; bildnummer <series->count;bildnummer++){
         einzelBild(px_ls, file, series, breite, hoehe, bildnummer);
@@ -100,7 +134,6 @@ void clearSeries(GrayScaleImageSeries *series)
                 free(series->images[i].buffer);
             }
         }
-        printf("Test\n");
         free(series->labels);
         free(series->images);
         free(series);
diff --git a/imageInputTests.c b/imageInputTests.c
index 03240ab..b92a58a 100644
--- a/imageInputTests.c
+++ b/imageInputTests.c
@@ -13,11 +13,11 @@ static void prepareImageFile(const char *path, unsigned short int width, unsigne
     if(file != NULL)
     {
         const char *fileTag = "__info2_image_file_format__";
-        GrayScalePixelType *zeroBuffer = (GrayScalePixelType *)calloc(numberOfImages * width * height, sizeof(GrayScalePixelType));
+        GrayScalePixelType *zeroBuffer = calloc(width * height, sizeof(GrayScalePixelType));
 
         if(zeroBuffer != NULL)
         {
-            fwrite(fileTag, sizeof(fileTag[0]), strlen(fileTag), file);
+            fwrite(fileTag, sizeof(const char), strlen(fileTag), file);
             fwrite(&numberOfImages, sizeof(numberOfImages), 1, file);
             fwrite(&width, sizeof(width), 1, file);
             fwrite(&height, sizeof(height), 1, file);
diff --git a/matrix.c b/matrix.c
index 29bdc8f..b996cb0 100644
--- a/matrix.c
+++ b/matrix.c
@@ -18,8 +18,9 @@ Matrix createMatrix(unsigned int rows, unsigned int cols) {
         }
         matrix.rows = rows;
         matrix.cols = cols;
-        memset(matrix.buffer, UNDEFINED_MATRIX_VALUE, rows*cols);
-
+        for (unsigned int i=0;i<rows*cols;i++){
+            matrix.buffer[i] = UNDEFINED_MATRIX_VALUE;
+        }
     }
 
     return matrix;
@@ -27,17 +28,21 @@ Matrix createMatrix(unsigned int rows, unsigned int cols) {
 
 void clearMatrix(Matrix *matrix)
 {
-    free(matrix->buffer);
-    matrix->rows = 0;
-    matrix->cols = 0;
-    matrix->buffer = NULL;
-    free(matrix->buffer);
+    if(matrix != NULL){
+        if(matrix->buffer != NULL)
+            free(matrix->buffer);
+        matrix->rows = 0;
+        matrix->cols = 0;
+        matrix->buffer = NULL;
+    }
 }
 
 void setMatrixAt(MatrixType value, Matrix matrix, unsigned int rowIdx, unsigned int colIdx)
 {
-    if(rowIdx<(matrix.rows) && colIdx<(matrix.cols)){
-        matrix.buffer[matrix.cols*rowIdx + colIdx]=value;
+    if(matrix.buffer != NULL){
+        if(rowIdx<(matrix.rows) && colIdx<(matrix.cols)){
+            matrix.buffer[matrix.cols*rowIdx + colIdx]=value;
+        }
     }
 }
 
@@ -59,6 +64,9 @@ Matrix add(const Matrix matrix1, const Matrix matrix2)
         output.rows = matrix1.rows;
         output.cols = matrix1.cols;
         output.buffer = malloc(sizeof(MatrixType)*output.rows*output.cols);
+        if(output.buffer == NULL){
+            return output;
+        }
         for (int i=0;i<matrix1.rows*matrix1.cols;i++){
             output.buffer[i]= matrix1.buffer[i]+matrix2.buffer[i];
         }
@@ -67,6 +75,9 @@ Matrix add(const Matrix matrix1, const Matrix matrix2)
         output.rows = matrix1.rows;
         output.cols = matrix1.cols;
         output.buffer = malloc(sizeof(MatrixType)*output.rows*output.cols);
+        if(output.buffer == NULL){
+            return output;
+        }
         for (int i=0;i<matrix2.rows;i++){
             for (int ii=0;ii<matrix1.cols;ii++){
                 output.buffer[(i*matrix1.cols)+ii]= matrix1.buffer[(i*matrix1.cols)+ii]+matrix2.buffer[i];
@@ -77,6 +88,9 @@ Matrix add(const Matrix matrix1, const Matrix matrix2)
         output.rows = matrix2.rows;
         output.cols = matrix2.cols;
         output.buffer = malloc(sizeof(MatrixType)*output.rows*output.cols);
+        if(output.buffer == NULL){
+            return output;
+        }
         for (int i=0;i<matrix1.rows;i++){
             for (int ii=0;ii<matrix2.cols;ii++){
                 output.buffer[(i*matrix2.cols)+ii]= matrix2.buffer[(i*matrix2.cols)+ii]+matrix1.buffer[i];
@@ -93,6 +107,9 @@ Matrix multiply(const Matrix matrix1, const Matrix matrix2)
         output.rows = matrix1.rows;
         output.cols = matrix2.cols;
         output.buffer = malloc(sizeof(MatrixType)*output.rows*output.cols);
+        if(output.buffer == NULL){
+            return output;
+        }
         for (int spalte2=0;spalte2<output.cols;spalte2++){
             for (int zeile1=0;zeile1<matrix1.rows;zeile1++){
                 for (int zeile2=0;zeile2<matrix2.rows;zeile2++){