A parameter is a named variable passed into a function. Parameter variables are used to import arguments into functions.

Note the difference between parameters and arguments:

  • Function parameters are the names listed in the function's definition.
  • Function arguments are the real values passed to the function.
  • Parameters are initialized to the values of the arguments supplied.

Two kinds of parameters:

input parameters
the most common kind; they pass values into functions. Depending on programming language, input parameters can be passed several ways (e.g., call-by-value, call-by-address, call-by-reference).
output/return parameters
primarily return multiple values from a function, but not recommended since they cause confusion

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