Dear,

GATE is a national level examination for admission in higher degree courses in IITs/NITs/IIITs and other public funded and private institutions and for the past few years it has also included qualifications for PSUs. As you mentioned your branch as CSE your primary paper should be GATE in Computer Science Engineering for a Mtech in CSE. A student can appear for minimum one and maximum two papers in GATE examination, second one being optional.