Chr(Expr1, Expr2, Variable1, Variable2, etc...)

Chr returns one character from the ASCII code it has been given. Chr, not unlike print can take several parameters, and even arrays, which it interprets as numeric values.

Return value:
A string composed of one or more characters, from the ASCII code(s) it has been given.

Example 1:

print(chr(90)$)

Z

Example 2:

clearArray(ac[])
ac[0] = 72
ac[1] = 69
ac[2] = 76
ac[3] = 76
ac[4] = 79
print(chr(ac[])$)

Hello

Notes:
ASCII stands for American Standard for Characters Interchange and Interface.
Numbers from 0 to 9 are coded with values from 48 to 57 respectively, and capital letters go from 65 (A) to 90 (Z). Note that adding 32 to a capital letter ASCII code brings the lower case equivalent.
ASCII is usually standard across platforms (PC, Mac, Unix...) except for the codes after 128. This is a problem for HTML pages where an accentuated letter will look fine on the original platform but will translate to another character on an other computer. That is why it is recommended to use character entities for all accentuated characters, i.e. é for 'é'.