Pointers vs. arrays (--selected from: C + + memory management Technology Insider)

Array:

Arrays are either created on a static store (such as a global array) or created on a stack. The array name represents

Contiguous memory, whose address and capacity will not change over the life cycle, but can only change its array contents.

Pointer:

A pointer is a pointer-type variable, and the variable is the first address of a memory that can be changed, so you can generally use pointers

To point to the dynamically opened memory.

The following is a string example to compare arrays and pointers :

1. Modify the Content

Char a[] = "Hello";
A[0] = ' X ';
cout << a << endl;//output is Xello
Char *p = "World"; Note P points to the constant string
P[0] = ' X '; The compiler cannot discover that the contents of the error//constant string cannot be modified.
cout << p << Endl;

2. Content replication and comparison

You cannot copy and compare directly to a group name. If you want to copy the contents of array A to array B, you cannot use statement B = A, otherwise
Generates a compilation error. The standard library function strcpy should be used for replication. Similarly, compare the contents of B and a are the same, not with if (b==a)
To judge, the standard library function strcmp should be used for comparison.
A is an array name, p is a pointer statement p = A does not copy the contents of a to pointer p, but assigns the address of A to P.

To Copy the contents of a, you can first use the library The function malloc for p applies a piece of memory with a capacity of strlen (a) + 1 characters, and then uses a strcpy

for string copying. Similarly, the statement if (p==a) comparison is not the content but the address, should be compared with the library function strcmp.

3. Calculate Memory capacity

Pointer p points to a, but sizeof (p) has a value of 4. This is because sizeof (p) Gets the number of bytes of a pointer variable, which is equivalent to
sizeof (char*), not the memory capacity referred to by P. The c++/c language has no way of knowing the amount of memory the pointer refers to, unless it is remembered in the application
when it is stored.
       char a[] = "Hello World";
       char *p = A;
       cout<< sizeof (a) << Endl;//12 bytes
& nbsp      cout<< sizeof (p) << Endl;//4 bytes, which represents the number of bytes that a character pointer occupies
        Note that when an array is passed as an argument to a function, the array is automatically degraded to a pointer of the same type. In the following example, sizeof (a) is always equal to sizeof (char *), regardless of the amount of
of the array A's capacity.
void Func (char a[100])
{
cout<< sizeof (a) << Endl;//4 bytes instead of 100 bytes
}

Pointers vs. arrays (--selected from: C + + memory management Technology Insider)