函数调用: - 绘制 方形 ((200,150) - 设 背景 颜色 ((黑) 变量: - x = 400 - y = 250
将给出的组件组装成一个功能性的计算机程序.
Here is an example of a functional computer program that assembles the given components:

```
# define the drawRectangle function
def drawRectangle(width, height):
  # code to draw a rectangle with given width and height

# define the setBackgroundColor function
def setBackgroundColor(color):
  # code to set the background color

# set values for x and y variables
x = 400
y = 250

# call the drawRectangle function with width 200 and height 150
drawRectangle(200, 150)

# call the setBackgroundColor function with color 'black'
setBackgroundColor('black')
```
Note that the specific code within the function definitions for drawRectangle and setBackgroundColor will depend on the specificities of the programming language and the graphics library being used.