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![]() | Section 5: Functions |
Now that you know what a function is, let's look at function syntax. We've already seen that a function can take some inputs, do some stuff, and then produce an output.
The basic form of a function definition is this:
It's called a function definition because we are defining the function. We are saying, "This is a function named function_name, whose inputs are input_1, input_2, etc., and whose output is output. When it is called, the function will execute the code in between its curly braces (output function_name ((input_1, input_2, input_3, input_...) { // code to execute inside function }
{}
).
At this point, let's refine our sample function definition. When programmers talk about functions, instead of the word input they usually use the word parameter. A parameter to a function is nothing more than an input to a function. At the same time, instead of using the word output, programmers generally refer to the return of a function. A particular function "returns" a value. So, here is our updated function definition:
return_type function_name ((parameter_1, parameter_2, parameter_3, parameter_...) { // code to execute inside function }
Notice that in place of output
, the function
definition says return_type. That's because when we
are actually writing a function definition, we'll put the
return type there, immediately preceding the name of the
function. The return type is nothing more than a plain old
variable type, such as int
, or double
, etc.
Similarly, parameters use variable types also. If the first
input to a function is an int
, then the first
parameter will be something like int my_number
.
We'll see what my_number
does in just a moment.
Enough dilly-dally, let's see a real, working, C++ function that actually does something! Suppose we need a function that, converts a temperature from Celsius to Fahrenheit. Here it is:
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