Define

Define.<type> [<variable> [= <expression>], <variable> [= <expression>], ...]

Assign the same data type to a series of variables.
Without this keyword, variables are created with the default type of PureBasic which is the type INTEGER. As a reminder, the type INTEGER is:
4 bytes (with a 32-bit compiler) ranging from -2147483648 to + 2147483647
8 bytes (with a 64-bit compiler) ranging from -9223372036854775808 to +9223372036854775807

Define is very flexible because it also allows you to assign a different type to a particular variable within a series.

Define can also be used with arrays, the lists and the maps.

Example: Serial assignment

   Define.b a, b = 10, c = b*2, d ; these 4 variables will be byte typed (.b)

Example: Mix of individual and serial assignments

   Define.q a, b.w, c, d, st.s = "ok"  ; a, c, and d are Quad (.q), b is a Word (.w) and st a String (.s)

   Debug SizeOf(a)  ; will print 8
   Debug SizeOf(b)  ; will print 2, because it doesn't have the default type
   Debug SizeOf(c)  ; will print 8 
   Debug SizeOf(d)  ; will print 8 
   Debug st         ; will print ok

Define <variable>.<type> [= <expression>] [, <variable>.<type> [= <expression>], ...] 

Alternative possibility for the variable declaration using Define.

Example

  Define MyChar.c 
  Define MyLong.l 
  Define MyWord.w 
  
  Debug SizeOf(MyChar)   ; will print 2
  Debug SizeOf(MyLong)   ; will print 4
  Debug SizeOf(MyWord)   ; will print 2