**Decimal and Hex**

Decimal is what we typically thing of when we thing of numbers. Decimal is simply the numbers 0 1 2 3 4 5 6 7 8 9. Decimal is also known as base 10, because there are 10 unique numbers.

Hexadecimal contains the follow numbers and letters: 0 1 2 3 4 5 6 7 8 9 A B C D E F. Hexadecimal is also known as base 16, because there are 16 unique values.In Hexadecimal, A has a value of 10, B 11, C 12, D 13, E 14, and E 15.

The hex function can be used to convert hexadecimal to decimal. For example, the "f" character in hexadecimal is the number 15 in decimal. The following Perl script would convert f to 15.

```
#!/usr/bin/perl
print hex 'f';
```

Hexadecimal strings are often predeeded with 0x. Appending 0x before a hexadecimal string will not impact the conversion of the string to decimal.

```
#!/usr/bin/perl
print hex '0xf';
```

Hex can just as well be used when reading or writing to a file.

```
$file = "/path/to/file.txt";
open(FH, '<', $file) or die "cannot open $file $! \n";
while (<FH>) {
print hex $_;
}
close(FH);
```

**Integer overflow**

The hex function may retur "Integer overflow in hexadecimal number" when using large hexadecimal strings.

```
Integer overflow in hexadecimal number at example.pl line x.
2.95147905179353e+20
```

The Math::BigInt module may be able to convert large hexadecimal strings to decimal.

```
#!/usr/bin/perl
use Math::BigInt;
$x = Math::BigInt->new("0xffffffffffffffffffffffff");
print $x;
```