diff --git a/Implementierung/src/io.c b/Implementierung/src/io.c
index 00840d2..339bd75 100644
--- a/Implementierung/src/io.c
+++ b/Implementierung/src/io.c
@@ -3,19 +3,20 @@
 bool open_file(const char* path, FILE** file, struct stat* file_stat) {
   (*file) = fopen(path, "r");
   if ((*file) == NULL) {
-    printf("Fopen error: %d\n", errno);
+    if (errno == 0) errno = EIO;
     return false;
   }
 
   int status = fstat(fileno((*file)), file_stat);
   if (status == -1) {
-    printf("Fstat error: %d\n", errno);
+    if (errno == 0) errno = EIO;
     fclose((*file));
     return false;
   };
 
   if ((file_stat->st_mode & S_IFMT) != S_IFREG) {
     printf("File is not a regular file!\n");
+    errno = ENOENT;
     fclose((*file));
     return false;
   }
@@ -38,8 +39,8 @@ uint8_t* read_file(const char* path, size_t* size) {
       fread(data, statOfFile.st_blksize, statOfFile.st_blocks, f);
   // size_t bytesRead = fread(data, sizeof(uint8_t), statOfFile.st_size, f);
   if (bytesRead != 0 && !feof(f)) {
-    printf("Error reading file!\n");
     fclose(f);
+    if (errno == 0) errno = EIO;
     return NULL;
   }
 
diff --git a/Implementierung/src/main.c b/Implementierung/src/main.c
index 08d26de..42b8e6f 100644
--- a/Implementierung/src/main.c
+++ b/Implementierung/src/main.c
@@ -74,10 +74,11 @@ bool calculate_hash(struct configuration c, char* hash) {
   }
 
   if (data == NULL) {
-    printf("Error reading file %s!", c.filename);
+    printf("Error reading file %s!\n", c.filename);
     return false;
   }
 
+  errno = 0;
   uint8_t out[16];
   if (c.doBenchmark) {
     double duration =
@@ -88,6 +89,10 @@ bool calculate_hash(struct configuration c, char* hash) {
     md2_hash(len, data, out);
   }
 
+  if (errno != 0) {
+    return false;
+  }
+
   md2_encode_hash(out, hash);
 
   if (c.implementationToUse != 2) free(data);
@@ -120,7 +125,7 @@ int main(int argc, char** argv) {
       c.implementationToUse, c.doBenchmark, c.benchmarkingCycles);
 
   if (c.runTests && c.implementationToUse == 2) {
-    fprintf(stderr, "Cannot run tests on implementation 2!");
+    fprintf(stderr, "Cannot run tests on implementation 2!\n");
     return EXIT_FAILURE;
   }
 
@@ -132,8 +137,14 @@ int main(int argc, char** argv) {
   printf("Hashing file %s...\n\n", c.filename);
 
   char hash[32];
-  calculate_hash(c, hash);
+  if (!calculate_hash(c, hash)) {
+    if (errno != 0) {
+      fprintf(stderr, "\n\033[0;31mAn error occured: %s\033[0m\n",
+              strerror(errno));
+    }
+    return EXIT_FAILURE;
+  }
   printf("Hash: %s\n", hash);
 
-  return 0;
+  return EXIT_SUCCESS;
 }
diff --git a/Implementierung/src/md2_impls/md2_2.c b/Implementierung/src/md2_impls/md2_2.c
index b51a47a..1349c0f 100644
--- a/Implementierung/src/md2_impls/md2_2.c
+++ b/Implementierung/src/md2_impls/md2_2.c
@@ -36,8 +36,6 @@ void apply_padding(size_t len, uint8_t buf[16]) {
     buf[len - paddingNeeded] = originalPadding;
     paddingNeeded--;
   }
-  printf("buf with padding: ");
-  md2_print_buf(len, buf);
 }
 
 // unused!
@@ -47,7 +45,6 @@ void md2_hash_2(size_t len, const uint8_t buf[len], uint8_t out[16]) {
   FILE* file;
   struct stat file_stat;
   if (!open_file((char*)buf, &file, &file_stat)) {
-    fprintf(stderr, "Error opening the file!\n");
     return;
   }
 
@@ -67,7 +64,7 @@ void md2_hash_2(size_t len, const uint8_t buf[len], uint8_t out[16]) {
 
     fread(data, 1, bytes_left_to_process, file);
     if (ferror(file) || feof(file)) {
-      fprintf(stderr, "Error reading the file!");
+      if (errno == 0) errno = EIO;
       return;
     }