## With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

No credit card required

# Converting Between ASCII Characters and Values

## Problem

You want to print out the number represented by a given ASCII character, or you want to print out an ASCII character given a number.

## Solution

Use `ord` to convert a character to a number, or use `chr` to convert a number to a character:

```\$num  = ord(\$char);
\$char = chr(\$num);```

The `%c` format used in `printf` and `sprintf` also converts a number to a character:

```\$char = sprintf("%c", \$num);                # slower than chr(\$num)
printf("Number %d is character %c\n", \$num, \$num);

`Number 101 is character e````

A `C*` template used with `pack` and `unpack` can quickly convert many characters.

```@ASCII = unpack("C*", \$string);
\$STRING = pack("C*", @ascii);```

## Discussion

Unlike low-level, typeless languages like assembler, Perl doesn’t treat characters and numbers interchangeably; it treats strings and numbers interchangeably. That means you can’t just assign characters and numbers back and forth. Perl provides Pascal’s `chr` and `ord` to convert between a character and its corresponding ordinal value:

```\$ascii_value = ord("e");    # now 101
\$character   = chr(101);    # now "e"```

If you already have a character, it’s really represented as a string of length one, so just print it out directly using `print` or the `%s` format in `printf` and `sprintf`. The `%c` format forces `printf` or `sprintf` to convert a number into a character; it’s not used for printing a character that’s already in character format (that is, a string).

`printf("Number %d is character %c\n", 101, 101);`

The `pack` , `unpack`, `chr`, and `ord` functions are all faster than `sprintf`. Here are `pack` and `unpack` in action:

```@ascii_character_numbers = unpack("C*", "sample");
print "@ascii_character_numbers\n";

`115 97 109 112 108 101`

\$word = pack("C*", @ascii_character_numbers);
\$word = pack("C*", 115, 97, 109, 112, 108, 101);   # same
print "\$word\n";

`sample````

Here’s how to convert from HAL to IBM:

```\$hal = "HAL";
@ascii = unpack("C*", \$hal);
foreach \$val (@ascii) {
\$val++;                 # add one to each ASCII value
}
\$ibm = pack("C*", @ascii);
print "\$ibm\n";             # prints "IBM"```

The `ord` function can return numbers from to 255. These correspond to C’s `unsigned` `char` data type.

The `chr`, `ord`, `printf`, `sprintf`, `pack`, and `unpack` functions in perlfunc(1) and Chapter 3 of Programming Perl