To declare variable types as integer, long, single-precision, double-precision, or string.
DEFtype letters[ - last_letter ][ , letter [ - last_letter ]]…
type is INT (integer), LNG (log integer), SNG (single-precision number), DBL (double-precision number), or STR (string of 0-255 characters).
letter and last_letter are a range of letters to associate with a type. QBasic does not distinguish between uppercase and lowercase variables.
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.
DEFINT L-P
All variables beginning with the letters L, M, N, O, and P will be integer variables.
DEFSTR A
A="120#"
All variables beginning with the letter A will be string variables. The $ declaration is unnecessary in this example.
DEFINT I-N, W-Z
W$="120#"
All variables beginning with the letters I, J, K, L, M, N, W, X, Y, Z will be integer variables. W$ establishes a string variable beginning with the letter W. However, the variable W will remain an integer elsewhere in the program.