username & pin

[kenneth6]

i am writing something about username and pin.

how can i filter the username contains only "a-z", "0-9", "." ONLY?
how can i filter the pin contains only "a-z", "A-Z", "0-9"? and what other symbols should be included?

how to ensure no space?

[Laharl]

Look up the functions in <ctype.h> or <cctype>, in particular isalpha() and isdigit(). To check for lowercase, you can check if it's between 'a' and 'z'.

[whodgson]

How do you look up what functions are in a header?

[Laharl]

Google or similar? Also, these are fairly self explanatory, I think.

[weaknessforcats]

How do you look up what functions are in a header?

Visual Studio? Press F1.