diff --git a/Makefile b/Makefile
index bfbfb93..31c58b1 100644
--- a/Makefile
+++ b/Makefile
@@ -43,8 +43,8 @@ SRC_SRCS_1 = nese.c ines.c
 SRC_SRCS_1 += nes.c ppu.c input.c
 SRC_SRCS_1 += cart.c mapper.c
 SRC_SRCS_1 += apu.c audio.c
-SRC_SRCS_1 += sdl_render.c sdl_input.c sdl_audio.c
-SRC_SRCS_1 += sdl_timer.c
+SRC_SRCS_1 += file.c save.c
+SRC_SRCS_1 += sdl_render.c sdl_input.c sdl_audio.c sdl_timer.c
 
 PLAT_SRCS_1 = filemap.c
 
diff --git a/src/cart.c b/src/cart.c
index e422b6f..043f937 100644
--- a/src/cart.c
+++ b/src/cart.c
@@ -57,6 +57,10 @@ int nes_cart_init_mem(nes_cart* cart, void* mem, int len) {
             cart->flags &= ~Cart_Flag_Horizontal;
         }
 
+        if (hdr->flags_6 & ines_Flag_Battery) {
+            cart->flags |= Cart_Flag_Battery;
+        }
+
         // Don't initialize the mapper until all flags are set!
         status = nes_map_init(cart->mapper, cart);
     }
diff --git a/src/cart.h b/src/cart.h
index 868a75f..eaa61c5 100644
--- a/src/cart.h
+++ b/src/cart.h
@@ -6,8 +6,9 @@
 
 
 typedef enum {
-    Cart_Flag_Vertical   = 0b0,
-    Cart_Flag_Horizontal = 0b1,
+    Cart_Flag_Vertical   = 0b00000000,
+    Cart_Flag_Horizontal = 0b00000001,
+    Cart_Flag_Battery    = 0b00000010,
 } nes_Cart_Flags;
 
 typedef struct nes_cart_t {
diff --git a/src/file.c b/src/file.c
new file mode 100644
index 0000000..77e4a27
--- /dev/null
+++ b/src/file.c
@@ -0,0 +1,69 @@
+#include <stdio.h>
+#include <string.h>
+
+#include "file.h"
+
+
+const char* basename(const char* filename) {
+    const char* slash = filename;
+    for ( ; *slash && *slash != '\\' && *slash != '/'; ++slash);
+    return (*slash ? (&slash[1]) : filename);
+}
+
+int replace_extension(char* filename, int max_len,
+                      const char* orig_name, const char* ext) {
+    int status = 0;
+    int remain = max_len;
+
+    const char* orig_base = basename(orig_name);
+    const char* orig_dot = strrchr(orig_base, '.');
+
+    int orig_base_len = (NULL == orig_dot) ?
+                        strlen(orig_name) :
+                        (orig_dot - orig_name);
+
+    if (orig_base_len <= remain) {
+        strncpy(filename, orig_name, orig_base_len);
+        remain -= orig_base_len;
+        filename += orig_base_len;
+    } else {
+        status = -1;
+    }
+
+    if (0 == status && NULL != ext) {
+        int ext_len = strlen(ext);
+        if ((ext_len + 1) <= remain) {
+            *filename++ = '.';
+            strncpy(filename, ext, ext_len);
+            remain -= (ext_len + 1);
+        } else {
+            status = -1;
+        }
+    }
+
+    return (status < 0 ? status : (max_len - remain));
+}
+
+
+int write_file(const char* filename, const void* data, int len) {
+    int status = -1;
+
+    FILE* file = fopen(filename, "wb");
+    if (NULL != file && 1 == fwrite(data, len, 1, file)) {
+        status = 0;
+    }
+
+    return status;
+}
+
+
+int read_file(const char* filename, void* data, int len) {
+    int status = -1;
+
+    FILE* file = fopen(filename, "rb");
+    if (NULL != file && 1 == fread(data, len, 1, file)) {
+        status = 0;
+    }
+
+    return status;
+}
diff --git a/src/file.h b/src/file.h
new file mode 100644
index 0000000..f7125fa
--- /dev/null
+++ b/src/file.h
@@ -0,0 +1,14 @@
+#ifndef NESE_FILE_H_
+#define NESE_FILE_H_
+
+
+// Return pointer to filename omitting path
+const char* basename(const char* filename);
+
+int replace_extension(char* filename, int max_len,
+                      const char* orig_name, const char* ext);
+
+int write_file(const char* filename, const void* data, int len);
+int read_file(const char* filename, void* data, int len);
+
+#endif // NESE_FILE_H_
diff --git a/src/map/mmc1.c b/src/map/mmc1.c
index 6fea88e..8c9ee14 100644
--- a/src/map/mmc1.c
+++ b/src/map/mmc1.c
@@ -9,6 +9,8 @@ typedef struct {
     uint8_t* chr_rom;
     int chr_rom_banks;
 
+    uint8_t battery;
+
     uint8_t reg_shift;
     uint8_t reg_n_shift;
     uint8_t reg_control;
@@ -117,6 +119,8 @@ static int mmc1_init(nes_mapper* nes_map, nes_cart* cart) {
             map->chr = map->chr_ram;
         }
 
+        map->battery = !!(cart->flags & Cart_Flag_Battery);
+
         mmc1_reset(nes_map);
     }
     return (NULL == map ? -1 : 0);
@@ -220,6 +224,17 @@ static uint8_t* mmc1_vram_addr(nes_mapper* nes_map,
 }
 
 
+static void* mmc1_sram(nes_mapper* nes_map) {
+    mmc1_mapper* map = (mmc1_mapper*)nes_map->data;
+    return (map->battery ? map->wram : NULL);
+}
+
+static int mmc1_sram_size(nes_mapper* nes_map) {
+    mmc1_mapper* map = (mmc1_mapper*)nes_map->data;
+    return (map->battery ? sizeof(map->wram) : 0);
+}
+
+
 nes_mapper mapper_mmc1 = {
     .name = "MMC1",
     .init = mmc1_init,
@@ -230,4 +245,7 @@ nes_mapper mapper_mmc1 = {
     .chr_addr = mmc1_chr_addr,
     .vram_addr = mmc1_vram_addr,
     .chr_write = mmc1_chr_write,
+
+    .sram_size = mmc1_sram_size,
+    .sram = mmc1_sram,
 };
diff --git a/src/map/mmc3.c b/src/map/mmc3.c
index 329e098..397276d 100644
--- a/src/map/mmc3.c
+++ b/src/map/mmc3.c
@@ -7,6 +7,7 @@ typedef enum {
     mmc3_Flag_IRQ_Enabled  = 0b00000010,
     mmc3_Flag_IRQ_Reload   = 0b00000100,
     mmc3_Flag_CHR_RAM      = 0b00001000,
+    mmc3_Flag_Battery      = 0b00100000,
     mmc3_Flag_WRAM_Protect = 0b01000000,
     mmc3_Flag_WRAM_Enabled = 0b10000000,
 } mmc3_Flag;
@@ -170,8 +171,14 @@ static int mmc3_init(nes_mapper* nes_map, nes_cart* cart) {
             map->chr_rom       = cart->chr_rom;
             map->chr_rom_banks = cart->chr_rom_banks * 4;
         }
+
+        if (cart->flags & Cart_Flag_Battery) {
+            map->flags |= mmc3_Flag_Battery;
+        }
+
         map->bank_select = mmc3_Bank_Select_PRG |
                            mmc3_Bank_Select_CHR;
+
         mmc3_reset(nes_map);
     }
     return (NULL == map ? -1 : 0);
@@ -323,6 +330,20 @@ static void mmc3_chr_write(nes_mapper* nes_map,
 //    MAP_LOG("CHR ROM Write: $%04x < %02x\n", addr, val);
 }
 
+
+static void* mmc3_sram(nes_mapper* nes_map) {
+    mmc3_mapper* map = (mmc3_mapper*)nes_map->data;
+    return (    (map->flags & mmc3_Flag_Battery) ?
+                map->wram : NULL);
+}
+
+static int mmc3_sram_size(nes_mapper* nes_map) {
+    mmc3_mapper* map = (mmc3_mapper*)nes_map->data;
+    return (    (map->flags & mmc3_Flag_Battery) ?
+                sizeof(map->wram) : 0);
+}
+
+
 nes_mapper mapper_mmc3 = {
     .name = "MMC3",
     .init = mmc3_init,
@@ -334,4 +355,7 @@ nes_mapper mapper_mmc3 = {
     .vram_addr = mmc3_vram_addr,
     .chr_write = mmc3_chr_write,
     .scanline = mmc3_scanline,
+
+    .sram_size = mmc3_sram_size,
+    .sram = mmc3_sram,
 };
diff --git a/src/mapper.h b/src/mapper.h
index 2e66892..deef8e5 100644
--- a/src/mapper.h
+++ b/src/mapper.h
@@ -31,6 +31,12 @@ typedef struct nes_mapper_t {
     void (*irq_callback)(void*, int);
     void* irq_arg;
 
+    void* (*sram)(struct nes_mapper_t*);
+    int (*sram_size)(struct nes_mapper_t*);
+
+    void (*save)(struct nes_mapper_t**);
+    int (*save_size)(struct nes_mapper_t*);
+
 } nes_mapper;
 
 static inline int nes_map_init(nes_mapper* map,
diff --git a/src/nese.c b/src/nese.c
index 1afa7e2..d221352 100644
--- a/src/nese.c
+++ b/src/nese.c
@@ -7,6 +7,8 @@
 #include "render.h"
 #include "input.h"
 #include "audio.h"
+#include "mapper.h"
+#include "save.h"
 
 
 #define audio_freq  (44100U)
@@ -25,17 +27,29 @@ static nes sys = {0};
 int main(int argc, char* argv[]) {
     int status = 0;
 
-    FILE* cart_file = stdin;
-    if (argc > 1) cart_file = fopen(argv[1], "rb");
-    if (NULL == cart_file) {
+    FILE* cart_file = NULL;
+    const char* cart_filename = NULL;
+    if (argc > 1) {
+        cart_filename = argv[1];
+        cart_file = fopen(argv[1], "rb");
+        if (NULL == cart_file) {
+            status = -1;
+            fprintf(stderr, "Could not open %s\n", argv[1]);
+        }
+    } else {
         status = -1;
-        fprintf(stderr, "Could not open %s\n", argv[1]);
+        fprintf(stderr, "Missing cartridge file\n");
     }
 
     if (status == 0) {
         status = nes_cart_init_file(&sys.cart, cart_file);
     }
 
+    if (status == 0) {
+        // Failure might mean there's nothing to load
+        load_sram(&sys.cart, cart_filename);
+    }
+
     nes_Renderer* rend = &sdl_renderer;
     if (status == 0) {
         status = nes_render_init(rend);
@@ -113,6 +127,13 @@ int main(int argc, char* argv[]) {
         fprintf(stdout, "Ran %f ms, %"PRIu64" master cycles (%s)\n",
                         ms_run, total_cycles,
                         status == 0 ? "OK" : "Halted");
+
+        // Failure might mean there's nothing to save
+        save_sram(&sys.cart, cart_filename);
+    }
+
+    if (cart_file != NULL) {
+        fclose(cart_file);
     }
 
     return status;
diff --git a/src/save.c b/src/save.c
new file mode 100644
index 0000000..9670d08
--- /dev/null
+++ b/src/save.c
@@ -0,0 +1,46 @@
+#include "save.h"
+#include "file.h"
+#include "mapper.h"
+
+
+static int make_sram_filename(char* sram_filename, int max_len,
+                              const char* cart_filename) {
+    return replace_extension(  sram_filename, max_len,
+                               basename(cart_filename), "sram");
+}
+
+int load_sram(nes_cart* cart, const char* cart_filename) {
+    int status = -1;
+
+    int sram_size = cart->mapper->sram_size ?
+            cart->mapper->sram_size(cart->mapper) : 0;
+    void* sram = cart->mapper->sram ?
+            cart->mapper->sram(cart->mapper) : NULL;
+
+    if (sram_size > 0 && NULL != sram) {
+        char sram_filename[FILENAME_MAX] = {0};
+        make_sram_filename(sram_filename, FILENAME_MAX - 1,
+                           cart_filename);
+        status = read_file(sram_filename, sram, sram_size);
+    }
+
+    return status;
+}
+
+int save_sram(const nes_cart* cart, const char* cart_filename) {
+    int status = -1;
+
+    int sram_size = cart->mapper->sram_size ?
+            cart->mapper->sram_size(cart->mapper) : 0;
+    const void* sram = cart->mapper->sram ?
+            cart->mapper->sram(cart->mapper) : NULL;
+
+    if (sram_size > 0 && NULL != sram) {
+        char sram_filename[FILENAME_MAX] = {0};
+        make_sram_filename(sram_filename, FILENAME_MAX - 1,
+                           cart_filename);
+        status = write_file(sram_filename, sram, sram_size);
+    }
+
+    return status;
+}
diff --git a/src/save.h b/src/save.h
new file mode 100644
index 0000000..7f5b310
--- /dev/null
+++ b/src/save.h
@@ -0,0 +1,11 @@
+#ifndef NESE_SAVE_H_
+#define NESE_SAVE_H_
+
+#include "cart.h"
+
+
+int load_sram(nes_cart* cart, const char* filename);
+int save_sram(const nes_cart* cart, const char* filename);
+
+
+#endif // NESE_SAVE_H_
diff --git a/src/sdl_input.c b/src/sdl_input.c
index 7c3a857..53eb4b5 100644
--- a/src/sdl_input.c
+++ b/src/sdl_input.c
@@ -39,6 +39,9 @@ static int sdl_input_init(nes_Input_Reader* reader) {
     if (status == 0) {
         reader->data = sdl_find_gamepad();
 //        SDL_SetEventFilter(sdl_event_filter, NULL);
+        if (NULL != reader->data) {
+            printf("Gamepad found\n");
+        }
     }
 
     return status;