diff --git a/hex2hcd.c b/hex2hcd.c
index 0f93937..896f79c 100644
--- a/hex2hcd.c
+++ b/hex2hcd.c
@@ -19,117 +19,132 @@
 
 #include <stdlib.h>
 #include <stdio.h>
+#include <string.h>
 #include <errno.h>
 
-#define RBUF_SIZE	640
+#define RBUF_SIZE 640
 
 static unsigned int asc_to_int(char a)
 {
-	if (a >= 'A')
-		return (a - 'A') + 10;
-	else
-		return a - '0';
+    return a >= 'A' ? (a - 'A') + 10 : a - '0';
 }
 
 static unsigned int hex_to_int(const char *h)
 {
-	return asc_to_int(*h) * 0x10 + asc_to_int(*(h + 1));
+    return asc_to_int(*h) * 0x10 + asc_to_int(*(h + 1));
 }
 
 static unsigned int lhex_to_int(const char *h)
 {
-	return hex_to_int(h) * 0x100 + hex_to_int(h + 2);
+    return hex_to_int(h) * 0x100 + hex_to_int(h + 2);
 }
 
 static int check_sum(const char *str, int len)
 {
-	unsigned int sum, cal;
-	int i;
-	sum = hex_to_int(str + len - 2);
-	for (cal = 0, i = 1; i < len - 2; i += 2)
-		cal += hex_to_int(str + i);
-	cal = 0x100 - cal & 0xFF;
-	return sum == cal;
+    unsigned int sum, cal;
+    int i;
+    sum = hex_to_int(str + len - 2);
+    for (cal = 0, i = 1; i < len - 2; i += 2)
+        cal += hex_to_int(str + i);
+    cal = 0x100 - cal & 0xFF;
+    return sum == cal;
 }
 
 static int check_hex_line(const char *str, int len)
 {
-	if ((str[0] != ':') || (len < 11) || !check_sum(str, len) ||
-		(hex_to_int(str + 1) * 2 + 11 != len))
-		return 0;
-	return 1;
+    if ((str[0] != ':') || (len < 11) || !check_sum(str, len) ||
+        (hex_to_int(str + 1) * 2 + 11 != len))
+        return 0;
+    return 1;
+}
+
+static FILE *open_file(const char *fileName, const char *mode) 
+{
+    FILE *file = fopen(fileName, mode);
+    if (!file) {
+        printf("The file '%s' could not be opened with the following reason\n", fileName);
+        puts(strerror(errno));
+        exit(-EIO);
+    }
+    return file;
 }
 
 int main(int argc, char *argv[])
 {
-	unsigned int addr = 0;
-	FILE *ifp, *ofp;
-	char *rbuf;
-	ssize_t len, i;
-	size_t buflen;
+    unsigned int addr = 0;
+    char *ifn, *ofn;
+    FILE *ifp, *ofp;
+    char *rbuf;
+    ssize_t len, i;
+    size_t buflen;
 
-	if (argc != 3) {
-		printf("Usage: %s <input hex file> <output file>\n", argv[0]);
-		return 0;
-	}
+    switch (argc) {
+        case 2:
+            ifn = ofn = argv[1];
+            break;
+        case 3:
+            ifn = argv[1];
+            ofn = argv[2];
+            break;
+        default:
+            printf("Usage: %s <input hex file> [<output file>]\n", argv[0]);
+            return 0;
+    }
 
-	ifp = fopen(argv[1], "r");
-	ofp = fopen(argv[2], "w");
-	if ((ifp == NULL) || (ofp == NULL)) {
-		puts("failed to open file.");
-		return -EIO;
-	}
+    ifp = open_file(ifn, "r");
+    ofp = open_file(ofn, "w");
+    
+    rbuf = NULL;
+    while (len = getline(&rbuf, &buflen, ifp)) {
+        int type;
+        char obuf[7];
+        unsigned int dest_addr;
 
-	rbuf = NULL;
-	while ((len = getline(&rbuf, &buflen, ifp)) > 0) {
-		int type;
-		char obuf[7];
-		unsigned int dest_addr;
-		while ((rbuf[len - 1] == '\r') || (rbuf[len - 1] == '\n'))
-			len--;
-		printf("%d, %s\n", (int)len, rbuf);
-		if (!check_hex_line(rbuf, len))
-			break;
-		type = hex_to_int(rbuf + 7);
-		switch (type) {
-			case 4:
-				addr = lhex_to_int(rbuf + 9) * 0x10000;
-				printf("bump addr to 0x%08X\n", addr);
-				break;
-			case 0:
-				dest_addr = addr + lhex_to_int(rbuf + 3);
-				obuf[0] = 0x4c;
-				obuf[1] = 0xfc;
-				obuf[2] = hex_to_int(rbuf + 1) + 4;
-				obuf[3] = dest_addr;
-				obuf[4] = dest_addr >> 8;
-				obuf[5] = dest_addr >> 16;
-				obuf[6] = dest_addr >> 24;
-				if (fwrite(obuf, 7, 1, ofp) != 1)
-					goto output_err;
-				for (i = 0; i < hex_to_int(rbuf + 1); i++) {
-					obuf[0] = hex_to_int(rbuf + 9 + i * 2);
-					if (fwrite(obuf, 1, 1, ofp) != 1)
-						goto output_err;
-				}
-				break;
-			case 1:
-				if (fwrite("\x4e\xfc\x04\xff\xff\xff\xff", 7, 1, ofp) != 1)
-					goto output_err;
-				goto end;
-			default:
-				return -EINVAL;
-		}
-	}
+        while ((rbuf[len - 1] == '\r') || (rbuf[len - 1] == '\n')) len--;
 
-	puts("hex file formatting error");
-	return -EINVAL;
+        printf("%d, %s\n", (int)len, rbuf);
 
-output_err:
-	puts("error on writing output file");
-	return -EIO;
+        if (!check_hex_line(rbuf, len)) break;
 
-end:
-	return 0;
+        type = hex_to_int(rbuf + 7);
+
+        switch (type) {
+            case 4:
+                addr = lhex_to_int(rbuf + 9) * 0x10000;
+                printf("Bump addr to 0x%08X\n", addr);
+                break;
+            case 0:
+                dest_addr = addr + lhex_to_int(rbuf + 3);
+                obuf[0] = 0x4c;
+                obuf[1] = 0xfc;
+                obuf[2] = hex_to_int(rbuf + 1) + 4;
+                obuf[3] = dest_addr;
+                obuf[4] = dest_addr >> 8;
+                obuf[5] = dest_addr >> 16;
+                obuf[6] = dest_addr >> 24;
+
+                if (fwrite(obuf, 7, 1, ofp) != 1) goto output_err;
+
+                for (i = 0; i < hex_to_int(rbuf + 1); i++) {
+                    obuf[0] = hex_to_int(rbuf + 9 + i * 2);
+                    if (fwrite(obuf, 1, 1, ofp) != 1) goto output_err;
+                }
+                break;
+            case 1:
+                if (fwrite("\x4e\xfc\x04\xff\xff\xff\xff", 7, 1, ofp) != 1) goto output_err;
+                goto end;
+            default:
+                return -EINVAL;
+        }
+    }
+
+    puts("Hex file formatting error");
+    return -EINVAL;
+
+    output_err:
+        puts("Error on writing output file");
+        return -EIO;
+
+    end: 
+        return 0;
 }
-