As you want to get the details of Common Admission Test which is organized by IIMs so here is the information of the same for you:

Eligibility Criteria:
Candidates must have passed graduation with minimum of 50% aggregate mark in graduation in any discipline from a recognized institute. The candidates from SC, ST, OBC and DA category need an aggregate of 45% marks. Final year graduation students can also apply provided they can submit the graduation final marks to the institutes within the requisite schedule.

Application Procedure:
Candidates have to register at the official CAT 2015 website and login through the given credentials.

Application Fees:
Rs 1600/= for General and NC-OBC candidates
Rs 800/= for SC/ST/PWD/ DA candidates

Exam Pattern:
Duration: 180 minutes with exact 60 minutes to answer each section.

The total number of questions is 100, divided into three sections. The three sections will be, Quantitative Aptitude (QA), Data Interpretation & Logical Reasoning (DILR) and Verbal and Reading Comprehension (VRC), in that order.

Selection Process:
The candidates are first shortlisted by IIMs and other participating B-schools on the basis of CAT cut off scores, followed by Personal Interview (PI) and Written Ability Test (WAT)/GD.

Important Dates:
Announcement of CAT 2015 by IIM Ahmedabad: Sunday, July 26, 2015
CAT 2015 Application Start Date: August 6, 2015
CAT 2015 Application End Date: September 25, 2015
CAT 2015 Admit Card Download starts: October 25, 2015
CAT 2015 Mock Test release: October 29, 2015
CAT 2015 Exam Date: November 29, 2015
CAT 2015 Result Date: Second week of January, 2016

As you can see the dates are of 2015. I have given these dates because the dates of 2016 have not been announced and these date scan be taken as tentative for the year of 2016

Syllabus of CAT:
Quantitative Ability Syllabus:
Number Systems
LCM and HCF
Percentages
Profit and Loss
Interest (Simple and Compound)
Speed, Time and Distance
Time and Work
Averages
Ratio and Proportion
Linear Equations
Quadratic Equations
Complex Numbers
Logarithm
Progressions
Binomial Theorem
Surds and Indices
Inequalities
Permutation and Combination
Probability
Functions
Set Theory
Mixtures and Alligations
Geometry
Co-ordinate Geometry
Trigonometry
Mensuration

Data Interpretation & Data Sufficiency:
Tables
Column graphs
Bar Graphs
Line charts
Pie Chart
Venn Diagrams

Logical Reasoning:
Number and Letter Series
Calendars
Clocks
Cubes
Venn Diagrams
Binary Logic
Seating Arrangement
Logical Sequence
Logical Matching
Logical Connectives
Syllogism
Blood Relations

Verbal Ability:
Vocabulary Based (Synonyms Antonyms)
English Usage or Grammar
Sentence Correction
Fill in the blanks
Cloze Passage
Analogies or Reverse Analogies
Jumbled Paragraph
Meaning-Usage Match
Summary Questions
Verbal Reasoning
Facts / Inferences / Judgements
Reading Comprehension