In Windows Operating system, The R installer will have created an icon for R on desktop and a Start Menu item. Double click the R icon to start the R Program; R will open the console, to type the R commands.
The greater than sing (>) in console is the prompt symbol. In this tutorial we will use R language as calculator (we will be Using R as Calculator for mathematical expressions), by typing some simple mathematical expressions at the prompt (>). Anything that can be computed on a pocket calculator can also be computed at the R prompt. After entering the expression on prompt, you have to press the Enter key from keyboard to execute the command. Some examples using R as calculator are as follows
> 1 + 2 #add two or more numbers
> 1 – 2 #abstracts two or more numbers
> 1 * 2 #multiply two or more numbers
> 1 / 2 #divides two more more numbers
> 1%/ %2 #gives the integer part of the quotient
> 2 ^ 1 #gives exponentiation
> 31 %% 7 #gives the remainder after division
These operators also works fine for complex numbers.
Upon pressing the enter key, the result of expression will appear, prefixed by a number in square bracket:
> 1 + 2
The  indicates that this is the first result from the command.
Some advance calculations that are available in scientific calculators can also be easily done in R for example
> sqrt(5) #Square Root of a number
> log(10) #Natural log of a number
> sin(45) #Trignometric function (sin function)
> pi #pi value 3.141593
> exp(2) #Antilog, e raised to a power
> log10(5) #Log of a number base 10
> factorial(5) #Factorial of a number e.g 5!
> abs(1/-2) #Absolute values of a number
> 2*pi/360 #Number of radian in one Babylonian degree of a circle
Remember R prints all very large or very small numbers in scientific notation.
R language also make use of parentheses for grouping operations to follow the rules for order of operations. for example
> 1-2/3 #It first computes 2/3 and then subtract it from 1
> (1-2)/3 #It first computes (1-2) and then divide it by 3
R recognizes certain goofs, like trying to divide by zero, missing values in data etc.
> 1/0 #Undefined, R tells it a infinity (Inf)
> 0/0 #Not a number (NaN)
> “one”/2 #Strings or character is divided by a number
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