SLB Senior Software Engineer interview questions

Got a call from consultant about the job profile for senior software engineer. Sent cv & got scheduled interview in week days. They called us at exact 8.45 but HR came at 9.30 & process started at 10.00. Very unplanned activity. The interview consisted of 4 rounds. 1. Presentation on any topic u choose u need to prepare at home. Need to presented in front of manager. My exp was good they are good listeners & receptive. 2. Subjective writtern: Dont know why they taken this because i doubt they are reading anything the candidate has written. 3. Technical round: through technical round OOPS, C#, WPF, WCF, database. 4. HR : major questions was why you switching & salary discussion.