File input/output is part of Short Circuit's Console Program Basics selection.
Task

Create a file called   "output.txt",   and place in it the contents of the file   "input.txt",   via an intermediate variable.

In other words, your program will demonstrate:

   how to read from a file into a variable
   how to write a variable's contents into a file


Oneliners that skip the intermediate variable are of secondary interest — operating systems have copy commands for that.




; open two LUNs
openw,unit1,'output.txt,/get
openr,unit2,'input.txt',/get
; how many bytes to read
fs = fstat(unit2)
; make buffer
buff = bytarr(fs.size)
; transfer content  
readu,unit2,buff
writeu,unit1,buff
; that's all
close,/all