# Character Combinations in The Alphabet

How to calculate the number of permutations in the alphabet. Also include a short table over permutations.

**64**views

By. Jacob

Edited: 2020-06-06 02:34

Sometimes it may be useful to know the number of character combinations in the alphabet for a given string length. We can calculate it by knowing the number of letters in the alphabet; since the English alphabet has 26 letters, we multiply *26*26=676* to find the number of letter combinations for a 2-character string.

**Note.** If you are trying to generate permutations of the alphabet progrematically, then beware that the total possible combinations will increase exponentially, and potentially exhaust system resources rather quickly. I have personally crashed my computer and lost work from fooling around with this stuff.

You probably should not generate permutations dynamically in programs. It may be better to keep a database or file with pre-generated permutations.

Here is table containing the number of possible letter combinations:

Length | Formula | Combinations | File? | Size |
---|---|---|---|---|

2 | 26*26 or 26^3 | 676 | alphabet-two-letter-combinations.txt | 2.1 kb |

3 | 26*26*26 or 26^3 | 17.576 | alphabet-three-letter-combinations.txt | 70.4 kb |

4 | 26*26*26*26 or 26^4 | 456.976 | alphabet-four-letter-combinations.txt | 2.3 mb |

5 | 26*26*26*26*26 or 26^5 | 11.881.376 | alphabet-five-letter-combinations.txt | 71.3 mb |

6 | 26*26*26*26*26*26 or 26^6 | 308.915.776 | Nope... Not doing it.. Do it yourself! |

**Note.** Each permutation in the files above is followed by a single line break (\n).

## Generate permutations from terminal

We do not necessarily need to create an algorithm for generating permutations. In Linux, it is also possible to generate permutations from a terminal with this very simple syntax: *{a..z}*.

To output all possible permutations of a two-letter string using the 26 letters of the alphabet:

```
echo {a..z}{a..z}
```

If you want to handle this in another programming language, such as PHP, you can create bash script and place it in *usr/local/bin/permutations_2x.sh*:

```
#!/bin/bash
echo {a..z}{a..z}
```

This can then be called from PHP with **shell_exec**:

```
echo shell_exec('permutations_2x.sh');
```

Since I use PHP a lot, I find *shell_exec* to be useful for interacting with other programs at times.

## Why are permutations interesting?

I have no idea. But, I personally had a need to generate all possible permutations of a two-letter string consisting of the 26 letters of the alphabet.

A two-letter string gives me 676 possible combinations, which should be more than enough to satisfy my needs. I was thinking that I wanted to try it out for shortening long text strings in order to save bandwidth for mobile users. It was also a nice little programming challenge to solve.

The alphabet is also an ideal candidate to practice on; once you have written an algorithm that works on the alphabet, you should also be able to use it on longer text strings.

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