The command-line arguments are transferred to the main function through

   int main (int argc, char* argv[])

The integer argc is the no of command-line arguments, set to one in our case, while argv is a vector of strings containing the command-line arguments with argv[0] containing the name of the program and argv[1], argv[2], ... are the command-line args, i.e., the number of lines of input to the program. Here we define floating points, see also below, through the keywords float for single precision real numbers and double for double precision. The function atof transforms a text (argv[1]) to a float. The sine function is declared in math.h, a library which is not automatically included and needs to be linked when computing an executable file.

With the command printf we obtain a formatted printout. The printf syntax is used for formatting output in many C-inspired languages (Perl, Python, Awk, partly C++).