To declare variable types as integer, single-precision, double-precision, or string.
DEFtype letters
type is INT (integer), SNG (single-precision number), DBL (double-precision number), or STR (string of 0-255 characters).
letters are letters (separated by commas) or range of letters of the alphabet.
A DEFtype statement declares that variable names beginning with the letter(s) specify that type of variable. However, a type declaration character (%,!,#,$) always takes precedence over a DEFtype statement in the typing of a variable.
If no type declaration statements are encountered, BASIC assumes all variables are single-precision. Single-precision is the default value.
10 DEFDBL L-P
All variables beginning with the letters L, M, N, O, and P will be double-precision variables.
10 DEFSTR A 20 A="120#"
All variables beginning with the letter A will be string variables. The $ declaration is unnecessary in this example.
10 DEFINT I-N, W-Z 20 W$="120#"
All variables beginning with the letters I, J, K, L, M, N, W, X, Y, Z will be integer variables. W$ in Line 20 establishes a string variable beginning with the letter W. However, the variable W will remain an integer elsewhere in the program.