Hi aspirant, Subject are easy nor tough. It depends on you how you give the effort on the perticular topics. For doing instrumental control you should have good foundation in an Electronics, Electrical , Thermodynamics, Physics, mathematics and control processing. But theory are tough than practical becomes weak. Theory and practical are directly propotional, you have to balance both. 

hi aravinth                                                                                                                   

you can find all the notes and topic ,syllabus for INSTRUMENTATION AND CONTROL SYSTEM - ICS on this site

https://lecturenotes.in/notes/14597-note-for-instrumentation-and-control-system-ics-by-jntu-heroes