Methods and Parameters

Parameters

Parameters let a method receive values from its caller.

parameter A parameter is a named input inside a method.

Parameters

width
Parameters.cs
Replay: real traced execution (multi-file project)
using System;

class Program
{
    static int Area(int width, int height)
    {
        return width * height;
    }

    static void Main()
    {
        int width = 5;
        int height = 4;
        int area = Area(width, height);

        Console.WriteLine($"width={width}");
        Console.WriteLine($"height={height}");
        Console.WriteLine($"area={area}");
    }
}

using System;

class Program
{
    static int Area(int width, int height)
    {
        return width * height;
    }

    static void Main()
    {
        int width = 3;
        int height = 4;
        int area = Area(width, height);

        Console.WriteLine($"width={width}");
        Console.WriteLine($"height={height}");
        Console.WriteLine($"area={area}");
    }
}

using System;

class Program
{
    static int Area(int width, int height)
    {
        return width * height;
    }

    static void Main()
    {
        int width = 7;
        int height = 4;
        int area = Area(width, height);

        Console.WriteLine($"width={width}");
        Console.WriteLine($"height={height}");
        Console.WriteLine($"area={area}");
    }
}

  1. width ← 5, height ← 4

    10static void Main()11{12    int width→ 5 = 5; //@width=3, 713    int height→ 4 = 4;14    int area = Area(width5, height4);

  2. static int Area(int width, int height)

    4{5    static int Area(int width5, int height4)6    {7        return width5 * height4;8    }

  3. area ← 20

    13    int height = 4;14    int area→ 20 = Area(width5, height4);1516    Console.WriteLine($"width={width5}");17    Console.WriteLine($"height={height4}");18    Console.WriteLine($"area={area20}");19}
    outputwidth=5
height=4
area=20

  1. width ← 3, height ← 4

    10static void Main()11{12    int width→ 3 = 3;13    int height→ 4 = 4;14    int area = Area(width3, height4);

  2. static int Area(int width, int height)

    4{5    static int Area(int width3, int height4)6    {7        return width3 * height4;8    }

  3. area ← 12

    13    int height = 4;14    int area→ 12 = Area(width3, height4);1516    Console.WriteLine($"width={width3}");17    Console.WriteLine($"height={height4}");18    Console.WriteLine($"area={area12}");19}
    outputwidth=3
height=4
area=12

  1. width ← 7, height ← 4

    10static void Main()11{12    int width→ 7 = 7;13    int height→ 4 = 4;14    int area = Area(width7, height4);

  2. static int Area(int width, int height)

    4{5    static int Area(int width7, int height4)6    {7        return width7 * height4;8    }

  3. area ← 28

    13    int height = 4;14    int area→ 28 = Area(width7, height4);1516    Console.WriteLine($"width={width7}");17    Console.WriteLine($"height={height4}");18    Console.WriteLine($"area={area28}");19}
    outputwidth=7
height=4
area=28

Follow the Parameters

  1. width starts as 5.
  2. height starts as 4.
  3. Area(width, height) passes both values into the method.
  4. Inside Area, width * height gives 20.
  5. The caller stores that result in area. | value passed | parameter | result part | | --- | --- | --- | | 5 | width | 5 * 4 | | 4 | height | 5 * 4 | | returned value | area | 20 |

Exercise: Parameters.cs

Reproduce width=5, height=4, and area=20, then use the pinned width variants 3 and 7 to predict area=12 and area=28.