What is the purpose of reverse command because I don't see any changes while using this command??
Reverses the vertices of selected lines, polylines, splines, and helixes, which is useful for linetypes with included text, or wide polylines with differing beginning and ending widths.
Vertices of selected objects are reversed.
For example, when a linetype with text is specified with relative rotation in a LIN file, the text in the linetype might be displayed upside down. Reversing the vertices of the object changes the orientation of the text.
The REVERSE command does not change the orientation of text where rotation is specified as upright.
In addition to other things already mentioned, another thing affected by the direction something is drawn is the placement of Points or Blocks in the MEASURE command. The specified spacing is measured from the "starting" end of the path object, and any leftover distance beyond a multiple of that spacing will be past the last Point or Block placed, at the "ending" end of the path. If you REVERSE the path object, the placements under MEASURE will then be measured from the other end from where they were before the REVERSE, and the results will [most of the time] be different.
Kent Cooper, AIA 
@elzohry2007 wrote:
....
The REVERSE command does not change the orientation of text where rotation is specified as upright.
That is the crucial thing to know in regard to Linetypes with either Text or Shapes embedded in them -- the difference between the R and U flags in the embedding code in the linetype definition. See Help about it [here for embedded Text, but the same for embedded Shapes]. If a Linetype is defined with the U flag for Text, you wouldn't see the change with REVERSE, because the Text parts would all go to the more upright orientation. But if the Linetype has, for example, an asymmetrical arrangement of dashes and gaps between Text parts, since those dashes and gaps are unaffected by the Text orientation but are affected by the drawn direction, REVERSE would change the upper one here to the lower one, or vice versa:
Kent Cooper, AIA
I think MEASURE command starts from the end which is closer to the pick up point, not depends on the direction of the linear object.
In civil engineering, we use special linetypes to indicate the flow (sewerage in this example)
It is also very useful when you draw a battered wall with a customized linetype. You can easily changed the battered wall direction with command REVERSE.
@3wood wrote:
I think MEASURE command starts from the end which is closer to the pick up point, not depends on the direction of the linear object.
You are correct [I wonder whether it worked as I thought long ago and has been changed, but I nearly never use it], except in the case of a CIRCLE, in which it measures CCW from the 0°-direction-from-the-center, no matter where you pick on it. But REVERSE won't work on a Circle anyway -- if you need something like a flow-direction or battered-wall linetype on a Circle, and need the linetype to go the other way, you would need to convert it to a Donut-type Polyline, such as with ReverseDirection.lsp >here<. Then the result in MEASURE would be affected by where you pick on it.
In experimenting about that, I discovered something unexpected that you might want to know about if you're using REVERSE on a closed Polyline, and if where it starts and ends matters: it doesn't simply change the direction from the starting vertex, but changes the starting vertex location!
Kent Cooper, AIA
@Anonymous wrote:
can you please give me simple straight forward definition of reverse command. I will ask you later if I feel problem on your definition.
>Help about it< is, I think, as simple and straight-forward as anything I could offer.
Kent Cooper, AIA
At least in one case you can not reverse a polyline.
As shown below, a polyline with 2 vertex but closed.
@3wood wrote:
At least in one case you can not reverse a polyline. .... a polyline with 2 vertex but closed.
It works for me:
The original was drawn with DONUT and equal inside and outside radii -- a zero-width two-half-circle-arc-segments closed Polyline. I even tried moving a vertex so it wasn't two equal arc segments, as in your image, but it still REVERSEd correctly.
Kent Cooper, AIA