Default value of a variable

What is the initial value of a variable before it being assigned a value? For different variable types, I have different initial values:

• (unsigned)int or (unsigned)long or bool(also arrays): 0
• (unsigned)long long: 1
• float: 0
• double: 4.94066e-324
• long double: 1.79581e+2383
• (unsigned or signed)char`: (doesn't output anything)
• double array: 3.23796e-319
• string:(unpredictable(random) value)
• ...

So why is default initial value like this for different var type?