program read_from_a_file

*This program reads in data from a file called a.dat,
*       and stores the data as an array called x(i). Then it 
*	takes a squared-root of every element in
*	x and write them in a file called b.dat.

	parameter(max=10000)
	real*4 x(max)


	open(2,file='/home/sgao/demo/07_f77/a.dat')
	do i=1,max
	read(2,*,end=222) x(i)
	print*,'x(', i, ') is ', x(i)
	enddo
222	close(2)

** The array is read. Now do some processing (taking the square-root of
*		each point) and write the results to b.dat

	open(1,file='b.dat')

	n=i-1
	do i=1,n
	y=sqrt(x(i))
	write(1,11) y
	write(6,11) y  !! also write to screen in addition to writing to unit 1
11	format(f10.4)
	enddo

	close(1)

	print*,'The output file is b.dat'

	stop
	end