Improve array slicing and examples example (#502)

Author: JorgeG94

source/learn/quickstart/arrays_strings.md

@@ -49,17 +49,37 @@ program array_slice
 
   integer :: i
   integer :: array1(10)  ! 1D integer array of 10 elements
+
   integer :: array2(10, 10)  ! 2D integer array of 100 elements
 
   array1 = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]  ! Array constructor
-  array1 = [(i, i = 1, 10)]  ! Implied do loop constructor
+  print *, "Array at odd indices"
+  print *, array1(1:10:2)  ! Print out elements at odd indices, start at element 1, go up to element 10, in strides of 2
+
+  print *, "Array in reverse!"
+  print *, array1(10:1:-1)  ! Print an array in reverse
+
   array1(:) = 0  ! Set all elements to zero
+  print *, "Reset array to 0!"
+  print *, array1
+
+  array1 = [(i, i = 1, 10)]  ! Implied do loop constructor
+  print *, "Now back to 1 to 10!"
+  print *, array1
+
+
   array1(1:5) = 1  ! Set first five elements to one
-  array1(6:) = 1  ! Set all elements after five to one
+  print *, "Set first five elements to 1"
+  print *, array1
+
+  array1(6:) = 2  ! Set all elements after five to two
+  print *, "Set all elements after 5 to 2"
+  print *, array1
 
-  print *, array1(1:10:2)  ! Print out elements at odd indices
+
+  print *, "First column of 2d array"
   print *, array2(:,1)  ! Print out the first column in a 2D array
-  print *, array1(10:1:-1)  ! Print an array in reverse
+
 
 end program array_slice
 ```