All you need to know about printf function

1. Before using printf you need to #include<stdio.h>.

2. The first argument to printf function is a string of characters which is called 'format string' or 'template'. If it is the only argument, this string is simply printed to the standard output (which by default is your terminal). For example,

   printf("hello\n");

   produces

   hello
   

   where the string \n represents the newline character.

3. Besides the first argument --- the format string --- printf can have more arguments which then must be the names of the variables (or expressions) which you want to print out. In this case the format string must contain placeholders for the arguments to be printed. The string is then printed with placeholders being replaced by the values of the given variables (expressions).

   By default the first argument after the format string takes the first placeholder, the second argument after the format string takes the second placeholder and so on.

   Placeholders must correspond to the types of arguments to be printed!

   We shall mostly print out numbers, therefore here are the simplest forms of placeholders for numbers,

   • integer: %i

     For example

     int n=123; printf("n = %i, twice n = %i, five times n = %i \n", n, 2*n, 5*n);
     

     produces

     n = 123, twice n = 246, five times n = 615
     

   • double: %g (actually %lg but %g seems to work somehow)

     For example

     double x=1.23; printf("x = %g, twice x = %g, five times x = %g \n", x, 2*x, 5*x);
     

     produces

     x = 1.23, twice x = 2.46, five times x = 6.15
     

   • long double: %Lg

4. The full description of format placeholders can be found in wikipedia or in the man pages man 3 printf.