Unable to access variable outside loop

Shell Programming and Scripting
1

I am unable to access the value set inside the loop from outside loop .
Thought of taking this to forum , I had seen other replies also , where a pipe takes the execution to another shell and mentioned thats the reason we do not get the variable outside loop . But I am getting an issue and I am not using pipe . A sample code below . I do not know where I am going wrong .Any help would be highly appreciated.
(note my tree1.txt contains only 1 line , just trying to test if I can access the value for a variable set inside a while loop)
*************
count=0
while read line
do
count=10
echo $count
done < tree1.lst
echo count:$count
************Result**********
10
count:0

2

You are using an old Bourne shell (perhaps /bin/sh on Solaris?).

Switch to a standard UNIX shell (/usr/xpg4/bin/sh or ksh).