thanks for reply.....

I am new to unix....
I require to append 100 spaces(fillers) to header(first line) and 100 space to trailer(last line).
the data in the middle not to be changed.

i do not want variable length record file turned into a fixed width record file. i just need to append 100 fillers in the first line and 100 fillers in last line

sample file:

HODA(need to add 100 fillers(spaces) here)
D0000000000000000000000000000000000
D0000000000000000000000000000000000
T000012(need to add 100 fillers(spaces) here)