diff --git a/crater.c b/crater.c
index 716259a..d26442b 100644
--- a/crater.c
+++ b/crater.c
@@ -16,7 +16,7 @@
 #define ROMS_DIR "roms"
 
 /* Print command-line help/usage. */
-static void print_help(char *arg1)
+static void print_help(const char *arg1)
 {
     printf("%s [--help|-h] [--version|-v] [rom_path]\n", arg1);
 }
@@ -54,7 +54,7 @@ static void parse_args(int argc, char *argv[])
 }
 
 /* Return whether the given string ends with the given suffix. */
-static bool ends_with(char *input, char *suffix)
+static bool ends_with(const char *input, const char *suffix)
 {
     size_t ilen = strlen(input), slen = strlen(suffix);
 
@@ -156,9 +156,11 @@ int main(int argc, char *argv[])
         else
             FATAL_ERRNO("couldn't load ROM image '%s'", rom_path)
     }
-    printf("Loaded ROM image: %s.\n", rom_path);
     if (argc <= 1)
         free(rom_path);
+    printf("Loaded ROM image: %s.\n", rom->name);
+
+    // TODO: start from here
 
     close_rom(rom);
     return 0;
diff --git a/src/rom.c b/src/rom.c
index f62e426..2621d29 100644
--- a/src/rom.c
+++ b/src/rom.c
@@ -3,12 +3,13 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 
 #include "rom.h"
 
 /* Create and return a ROM object located at the given path. Return NULL if
    there was an error; errno will be set appropriately. */
-rom_type* open_rom(char *path)
+rom_type* open_rom(const char *path)
 {
     rom_type *rom;
     FILE* fp;
@@ -17,9 +18,12 @@ rom_type* open_rom(char *path)
         return NULL;
     if (!(rom = malloc(sizeof(rom_type))))
         return NULL;
+    rom->name = malloc(sizeof(char) * (strlen(path) + 1));
+    strcpy(rom->name, path);
 
     // load data from file into a buffer
 
+    fclose(fp);
     return rom;
 }
 
diff --git a/src/rom.h b/src/rom.h
index 63288a1..a28f9c4 100644
--- a/src/rom.h
+++ b/src/rom.h
@@ -12,5 +12,5 @@ typedef struct {
 
 /* Functions */
 
-rom_type* open_rom(char*);
+rom_type* open_rom(const char*);
 void close_rom(rom_type*);
diff --git a/src/z80.h b/src/z80.h
index afae3a2..020cf1f 100644
--- a/src/z80.h
+++ b/src/z80.h
@@ -3,6 +3,11 @@
 
 #pragma once
 
+/* Clock speed in Hz was taken from the official Sega GG documentation */
+#define CLOCK_SPEED 3579545
+
+/* Structs */
+
 typedef struct {
     int pc;
-} register_type;
+} z80_type;