First of all if you are panic,calm down.Just prepare well for aptitude and basic OOP concepts,then if time permits go in depth of the your subjects. I applied through campus.Cognizant was first company in day-zero companies.There were almost 1000 students who applied for this post. It was a two days process.At first day Aptitude and the selected ones gets in for Tech interview followed by HR interview on second day. First round was of aptitude which was quite easy and was took by Aspiring Minds,in which around 250 students were selected and luckily i was one of them. Then there was technical interview which was also quite easy as the interviewer was a very benign person.First he asked me whether I ate anything or not and tried to calm me down and made me comfortable. He asked very simple and instant questions.Most of the question he asked me from my resume to check the authenticity of resume.Then he asked about basic concepts of OOP and gave one simple program with real life scenario in C or C++. I answered most of the questions. Then after 5 minutes i got called and told to go for HR interview.There was only one interviewer,he asked basic HR questions and asked to make him understand one of my project by considering him lay person. Then he asked me to sign on disclosure letter after reading last two lines. After 12 days result came,around 70 candidates were selected and i was one of 'em. Best of luck guys \m/.