140831 ● value type and reference type

Stack and stack differences

When the computer allocates memory, the heap and stack areas are separated.

1. Heap: It is generally assigned and released by programmers to store strings and arrays.

2. STACK: used to store function parameter values and local variable values.

For ease of understanding, you can think of the heap as a warehouse, and the stack as a record and index of the warehouse.

Value Type and reference type

Value types include integer, numeric, Boolean, floating point, and custom struct. The value type is stored in the stack area of the memory.

The reference types include arrays and strings. The reference type is stored in the heap area of the memory.

 

1 static void Hello (string a) 2 {3 A = "hello"; 4 console. writeline ("2," + a); 5} 6 7 static void main (string [] ARGs) 8 {9 string n = "hello"; 10 console. writeline ("1," + n); 11 Hello (n); 12 console. writeline ("3," + n); 13 14}

 

We all know that the string is of the reference type, the address passing method, analysis of the above Code, for beginners, may think the output result is: 1, hello; 2, hello; 3, hello. But actually:

Why is the actual display different?

Analysis: the string is stored in the heap area of the memory. The string is actually a character array and the length of the array cannot be changed. Therefore, when you assign a value to the string variable, the computer creates a new string in the heap area and assigns the address to the variable. In row 3, when n = "hello" is defined, the string "hello" is created in the heap area, and the variable N is created in the stack area, N stores the address "hello" in the heap area. When the program runs on Row 3, the computer actually creates "hello" in the heap area and sends the address to the form parameter A of the stack area. During this process, the address "hello" is stored in stack area n.

 

 

　　

140831 ● value type and reference type