C Functionality

In Part 1-2, we talked a little about functions in order to understand what main() was. Here we will take a much more detailed tour through functions.

Consider the program:

#include <stdio.h>
#include <math.h>

float pythag( float side_a, float side_b ) ;
float square( float x ) ;

main()
{
   float adjacent, opposite, hypotenuse ;

   printf( "What lengths are the adjacent and opposite sides? " ) ;
   scanf( "%f%f", &adjacent, &opposite ) ;
   hypotenuse = pythag( adjacent, opposite ) ;
   printf( "The lenght of the hypotenuse is %f\n", hypotenuse ) ;
}

float pythag( float side_a, float side_b )
{
   return( sqrt( square( side_a ) + square( side_b ))) ;
}

float square( float x )
{
   return( x * x ) ;
}

(We've left out the comments as we will do in most of the examples in this tutorial.)

Looking at the functions for pythag() and square() at the bottom of the program, we see that they look a lot like the function declarations for main that we've already seen, but with some additional features. (Ignore the pythag and square at the beginning of the program for now. We'll see what that's for in Part 2-5.) In particular they specify parameters and return types. The function:

float square( float x )
{
   return( x * x ) ;
}

can be read as the C translation of the English sentence:

The floating point square of a floating point number, x, is given by x * x.

The first float, as in float square(..., specifies that the function square will return a floating point number as its result. The float x inside the parentheses specified that square will take one argument (or parameter) which is a floating point number and it will be called x inside the function. If the function takes more than one parameter, then we list them separated by commas as in the definition of pythag().

Give the first line of a function definition (up to but not including the opening brace ({)) for a function called conv that takes an integer argument (call it x) and produces a character as output. (Remember Part 1-4 lists some of the common data types in C.)