R can be used as an ordinary calculator, some say it is an over-grown calculator. Here are some examples. Remember # is the comment character. The comments give details about the operations in case they are not clear.
2 + 3 * 5 # Note the order of operations.
log(10) # Natural logarithm with base e
5^2 # 5 raised to the second power
3/2 # Division
sqrt(16) # Square root
abs(3-7) # Absolute value of 3-7
pi # The number
exp(2) # exponential function
# This is a comment line