What is the difference between char *a and char a[]?

How Char a[] Works ?

• Consider "Hello" String is stored in Character Array 'a'.
• "HELLO" is Stored in Character Array [ in Contiguous Memory Location.]
• It will take Following Form after Initialization.

Initialization :

char a[] = "HELLO";

What Happens ?

• Here Array Size is not Specified .
• So C Assigns Individual Character to Each Array Location  -

a[0] = 'H'
a[1] = 'E'
a[2] = 'L'
a[3] = 'L'
a[4] = 'O'
a[5] = '\0'

It will Looks Like This ...

How a[3] Works Here ?

1. Compiler Finds a[3].
2. Compiler Checks Whether a is Array or Pointer ?
3. If 'a' is Array Variable then It starts at the location "a", goes three elements past it, and returns the character there
4. So Access is Sequential.

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How Char *a Works ?

• Consider "Hello" String is stored in Anonymous Character Array.
• It will take Following Form after Initialization.

Initialization :

char *a = "HELLO";

• 'a' is Pointer Variable.
• 'a' Stores Base Address of the Anonymous Array [Unknown Array]
• Whenever a[3] is to be accessed then In one shot Following Memory Location is Accessed -

Address = [Base Address of Anonymous Array]
          +
          [i]

• So In Short if a is a pointer, it starts at the location "a", gets the pointer value there, adds 3 to the pointer value, and gets the character pointed to by that value

In both Cases a[3] returns same Character but Procedure is Different.
Related Article :

• What Different Styles of Initializing String Type Variable ?

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Tags / Keywords : | char *a, char a[], Character Array, Initialization of Strings

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