Question: How do I determine if a `char` in C such as `a` or `9` is a number or a letter?

Is it better to use:

```
int a = Asc(theChar);

```

or this?

```
int a = (int)theChar

```

Answer: 
chars are just integers, so you can actually do a straight comparison of your character against literals:

```
if( c >= '0' && c <= '9' ){

```

This applies to all characters. [See your ascii table](http://www.asciitable.com/).

[ctype.h](http://www.acm.uiuc.edu/webmonkeys/book/c_guide/2.2.html) also provides functions to do this for you.
Neither of these does anything useful. Use `isalpha()` or `isdigit()` from the standard library. They're in `<ctype.h>`.