diff --git a/21st_century_c/process_dir.c b/21st_century_c/process_dir.c
new file mode 100644
index 0000000..8132eb5
--- /dev/null
+++ b/21st_century_c/process_dir.c
@@ -0,0 +1,53 @@
+#include "process_dir.h"
+#include <dirent.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+
+int process_dir_r(filestruct level) {
+  if (!level.fullname) {
+    if (level.name) {
+      level.fullname = level.name;
+    } else {
+      level.fullname = ".";
+    }
+  }
+  int errct = 0;
+
+  DIR *current = opendir(level.fullname);
+  if (!current) {
+    return 1;
+  }
+
+  struct dirent *entry;
+  while ((entry = readdir(current))) {
+
+    if (entry->d_name[0] == '.') {
+      continue;
+    }
+
+    filestruct next_level = level;
+    next_level.name = entry->d_name;
+    (void) asprintf(&next_level.fullname, "%s/%s", level.fullname, entry->d_name);
+    if (next_level.fullname == NULL) {
+      return 1;
+    }
+
+    if (entry->d_type == DT_DIR) {
+      next_level.depth++;
+      if (level.directory_action) {
+        level.directory_action(next_level);
+      }
+      errct += process_dir_r(next_level);
+    } else if (entry->d_type == DT_REG && level.file_action) {
+      level.file_action(next_level);
+      errct += next_level.error;
+    }
+
+    if (next_level.fullname) {
+      free(next_level.fullname);
+    }
+  }
+  closedir(current);
+  return errct;
+}
diff --git a/21st_century_c/process_dir.h b/21st_century_c/process_dir.h
new file mode 100644
index 0000000..2dec565
--- /dev/null
+++ b/21st_century_c/process_dir.h
@@ -0,0 +1,17 @@
+struct filestruct;
+typedef void (*level_fn)(struct filestruct path);
+
+
+typedef struct filestruct
+{
+  char *name, *fullname;
+  level_fn directory_action, file_action;
+  int depth, error;
+  void *data;
+} filestruct;
+
+
+
+#define process_dir(...) process_dir_r((filestruct){__VA_ARGS__})
+
+int process_dir_r(filestruct level);
diff --git a/21st_century_c/show_tree.c b/21st_century_c/show_tree.c
new file mode 100644
index 0000000..230e714
--- /dev/null
+++ b/21st_century_c/show_tree.c
@@ -0,0 +1,29 @@
+#include <stdio.h>
+#include "process_dir.h"
+
+
+void print_dir(filestruct in) {
+  for (size_t i = 0; i < in.depth-1; ++i) {
+    printf("    ");
+  }
+  printf("├ %s\n", in.name);
+  for (size_t i = 0; i < in.depth-1; ++i) {
+    printf("    ");
+  }
+  printf("└───┐\n");
+}
+
+
+void print_file(filestruct in) {
+  for (size_t i = 0; i < in.depth; ++i) {
+    printf("    ");
+  }
+  printf("│ %s\n", in.name);
+}
+
+
+int main (int argc, char **argv) {
+  char *start = (argc > 1) ? argv[1] : ".";
+  printf("Tree for %s:\n", start ? start : "the current directory");
+  process_dir(.name=start, .file_action=print_file, .directory_action=print_dir);
+}