Need to insert text(constant) at the beginning of file

I am very new to scripting and I know this request is simple but I am having no luck with it.

I have a file a.dat with the following data in it.
aa
bb
cc
dd

I need to run a script that will take each line of a.dat and put dsjc/ubin/ in front of each record, so the output looks like

dsjc/ubin/aa
dsjc/ubin/bb
dsjc/ubin/cc
dsjc/ubin/dd

Thanks in advance for your help.

sed 's+^+dscj/ubin/+' a.dat

the caret ^ matches beginning of the line, + is a delimiter, can be any char that is not in the pattern.

Awesome!!!!!!!!!!!
Thanks so much.