Address offset in the C language Array

In C/C ++, address offsets in one-dimensional arrays and two-dimensional arrays are discussed.

One-dimensional array int a [3];

Two-dimensional array int a [3] [3];

 

1. first look at the situation of one-dimensional arrays:

[Cpp]
# Include <iostream>
 
Using namespace std;
 
Int main ()
{
Int a [3] = {1, 2, 3 };

Cout <& a <endl;
Cout <a <endl;
Cout <& a [0] <endl;
Cout <a [0] <endl;
 
Cout <& a + 1 <endl;
Cout <a + 1 <endl;
Cout <& a [0] + 1 <endl;
Cout <a [0] + 1 <endl;
 
System ("pause ");
Return 0;
}

# Include <iostream>

Using namespace std;

Int main ()
{
Int a [3] = {1, 2, 3 };
 
Cout <& a <endl;
Cout <a <endl;
Cout <& a [0] <endl;
Cout <a [0] <endl;

Cout <& a + 1 <endl;
Cout <a + 1 <endl;
Cout <& a [0] + 1 <endl;
Cout <a [0] + 1 <endl;

System ("pause ");
Return 0;
}

 

The result shows that & a, a, and & a [0] indicate the same address, but the level is different.

The & a + 1 Address and & a offset is 12 bytes, indicating the space size of the array;

The a + 1 address is 4 bytes different from the address, that is, the space size of an element in the array;

The address & a [0] + 1 is 4 bytes offset from the address & a [0], that is, the space size of an element in the array;

That is to say, & a, a, and & a [0] indicate the same address, but the compiler will differentiate them. & a points to the address of the entire array, which is the most advanced address in the array, a and & a [0] indicate that & a represents the next level of address.

 
 

2. Two-dimensional array

[Cpp]
# Include <iostream>
 
Using namespace std;
 
Int main ()
{
Int a [3] [3] = {1, 2, 3}, {4, 5, 6}, {7, 8, 9 }};
 
Cout <& a <endl;
Cout <a <endl;
Cout <& a [0] <endl;
Cout <a [0] <endl;
Cout <& a [0] [0] <endl;
Cout <a [0] [0] <endl;
 
Cout <& a + 1 <endl;
Cout <a + 1 <endl;
Cout <& a [0] + 1 <endl;
Cout <a [0] + 1 <endl;
Cout <& a [0] [0] + 1 <endl;
Cout <a [0] [0] + 1 <endl;
 
System ("pause ");
Return 0;
}

# Include <iostream>

Using namespace std;

Int main ()
{
Int a [3] [3] = {1, 2, 3}, {4, 5, 6}, {7, 8, 9 }};

Cout <& a <endl;
Cout <a <endl;
Cout <& a [0] <endl;
Cout <a [0] <endl;
Cout <& a [0] [0] <endl;
Cout <a [0] [0] <endl;

Cout <& a + 1 <endl;
Cout <a + 1 <endl;
Cout <& a [0] + 1 <endl;
Cout <a [0] + 1 <endl;
Cout <& a [0] [0] + 1 <endl;
Cout <a [0] [0] + 1 <endl;

System ("pause ");
Return 0;
}

 
 

Result Analysis:

& A, a, & a [0], a [0], and & a [0] [0] indicate the same address, but the level difference is large.

The declared int a [3] [3] is 36 bytes in size.

The & a + 1 Address and & a offset is 36 bytes, indicating the space size of the array;

The a + 1 address is a-byte offset of 12 bytes, that is, the space size of a row of elements in the array;

The address & a [0] + 1 is offset by 12 bytes compared with & a [0], that is, the space size of a row of elements in the array;

The address a [0] + 1 is 4 bytes different from the address a [0], that is, the space size of an element in the array;

& A [0] [0] + 1 address is 4 bytes offset compared with & a [0] [0], that is, the space size of an element in the array;

As can be seen from the above, & a is the highest level of address, and a + 1 and & a [0] + 1 are the second level of address, a [0] + 1 and & a [0] [0] + 1 represent the third-level address in a two-dimensional array.