How do you convert a string to binary for manipulation?

Eg. 0001000 is the string
I want to separate it out into an array format such that
a[0]=0, a[1]=0... a[3]=1 ... a[6] = 0
for manipulation.

After that I wish to get the string again by appending the values together. Can I do something like
string = a[0] + a[1] + a[2]...

andrew