diff --git a/backend/library.c b/backend/library.c
index edec5210..2cdc57f2 100644
--- a/backend/library.c
+++ b/backend/library.c
@@ -48,7 +48,7 @@ struct zint_symbol *ZBarcode_Create()
 	symbol->width = 0;
 	strcpy(symbol->fgcolour, "000000");
 	strcpy(symbol->bgcolour, "ffffff");
-	strcpy(symbol->outfile, "out.png");
+	strcpy(symbol->outfile, "");
 	symbol->scale = 1.0;
 	symbol->option_1 = -1;
 	symbol->option_2 = 0;
@@ -590,7 +590,9 @@ int ZBarcode_Encode(struct zint_symbol *symbol, unsigned char *source, int lengt
 		return ERROR_INVALID_DATA;
 	}
 
-	
+	if(strcmp(symbol->outfile, "") == 0) {
+		strcpy(symbol->outfile, "out.png");
+	}
 #ifndef _MSC_VER
         unsigned char local_source[length + 1];
 #else
diff --git a/frontend/main.c b/frontend/main.c
index cc42a731..b0c15746 100644
--- a/frontend/main.c
+++ b/frontend/main.c
@@ -201,7 +201,7 @@ int batch_process(struct zint_symbol *symbol, char *filename)
 	
 	memset(buffer, 0, sizeof(unsigned char) * 7100);
 	if(symbol->outfile[0] == '\0') {
-		strcpy(format_string, "$$$$$.png");
+		strcpy(format_string, "~~~~~.png");
 	} else {
 		if(strlen(format_string) < 127) {
 			strcpy(format_string, symbol->outfile);
@@ -241,11 +241,11 @@ int batch_process(struct zint_symbol *symbol, char *filename)
 				local_line_count /= 10;
 				inpos++;
 			} while (local_line_count > 0);
+			number[inpos] = '\0';
 			
 			for(i = 0; i < inpos; i++) {
 				reverse_number[i] = number[inpos - i - 1];
 			}
-
 			
 			format_len = strlen(format_string);
 			for(i = format_len; i > 0; i--) {
@@ -260,7 +260,7 @@ int batch_process(struct zint_symbol *symbol, char *filename)
 							adjusted[0] = ' ';
 						}
 						break;
-					case '$':
+					case '~':
 						if (inpos > 0) {
 							adjusted[0] = reverse_number[inpos - 1];
 							inpos--;
@@ -268,7 +268,7 @@ int batch_process(struct zint_symbol *symbol, char *filename)
 							adjusted[0] = '0';
 						}
 						break;
-					case '*':
+					case '@':
 						if (inpos > 0) {
 							adjusted[0] = reverse_number[inpos - 1];
 							inpos--;