diff --git a/Makefile b/Makefile
index e30beb3..c68511f 100644
--- a/Makefile
+++ b/Makefile
@@ -1,12 +1,12 @@
 CC=bcc
 CFLAGS=-Md -W
 
-all: brmbar.c
+all: brmbar.c defines.h
 	gcc -Wall brmbar.c -o brmbar
 	bcc -Md -W brmbar.c -o brmbar.com
 
 clean:
-	rm -f brmbar.com
+	rm -f brmbar.com brmbar
 
 dos:
 	dosbox brmbar.com
diff --git a/dataio.c b/dataio.c
new file mode 100644
index 0000000..4dd42f8
--- /dev/null
+++ b/dataio.c
@@ -0,0 +1,39 @@
+#include <stdio.h>
+#include <string.h>
+#include "dataio.h"
+
+int modify_credit(name, price)
+    const char* name;
+    int price;
+{
+    char filename[13];
+    int i;
+    int credit;
+    FILE* person_data;
+
+    strncpy(filename, name, 8);
+    i = strlen(name);
+    if (i > 8) i = 8;
+    strcpy(&filename[i], ".txt");
+    person_data = fopen(filename, "r");
+
+    if (person_data == NULL) {
+        printf("Warning: Filename %s does not exist! Creating...\n", filename);
+        credit = 0;
+    } else {
+        fscanf(person_data, "%i", &credit);
+        fclose(person_data);
+    }
+
+    credit += price;
+    person_data = fopen(filename, "w");
+    if (person_data == NULL) {
+        printf("ERROR: Filename %s could not be created or overwritten!\nCheck system integrity!\n", filename);
+    } else {
+        fprintf(person_data, "%i", credit);
+        fclose(person_data);
+    }
+
+    return credit;
+}
+
diff --git a/dataio.h b/dataio.h
new file mode 100644
index 0000000..3e7d340
--- /dev/null
+++ b/dataio.h
@@ -0,0 +1,7 @@
+#ifndef _BRMBAR_DATAIO_H_
+#define _BRMBAR_DATAIO_H_
+
+extern int modify_credit(name, price);
+
+#endif
+