A Word About Calculators
You are probably very used to using a calculator and other kinds of technology in your high school math classes. You may find the use of calculators in University of Iowa math classes is limited. It is expected that freshmen entering the UI are proficient in arithmetic with integers and fractions without the use of calculators. Calculators are used to confirm algebraic solutions to equations, reasonability of limits of functions and slopes of tangent lines in calculus but you should be able to solve equations like 36x3 = -4/3 easily without a calculator
You will probably find that graphing calculators are less used in UI classes than in your high school classes. It is departmental policy that the use of technology in a class is left up to the instructor of each course. This may range from not allowing even a scientific calculator to requiring a certain graphing calculator or that you learn to do assignments on Maple or Mathematica. Most instructors do not allow graphing calculators or calculators doing symbolic algebra on quizzes or exams.
You need to develop a good number sense and the kind of familiarity with numbers that comes from use of paper and pencil techniques for acquiring skills in arithmetic.