What's the Difference Between `*ptr `, ` *ptr`, and ` ptr` in C?

Understanding Pointer Expressions: ptr , ptr, and *ptr

In C programming, these three expressions are commonly used to manipulate pointers and the values they point to. Understanding their behavior is crucial for effectively working with pointers.

1. *ptr

• This expression effectively dereferences the pointer first, returning the value it points to.
• Then, it increments the pointer by one unit, pointing it to the next element in the array or the next character in the string.
• For example, if ptr points to the first element of an array, *ptr will return the value of that element and then increment ptr to point to the second element.

2. * ptr

• Unlike the previous expression, this one first increments the pointer by one unit.
• Then, it dereferences the pointer, returning the value the pointer now points to.
• This is useful when you need to access the value of the next element without dereferencing the current pointer.

3. *ptr

• This expression directly increments the value at the location pointed to by ptr.
• It first dereferences the pointer, returning the value it points to.
• Then, it increments the value by one unit.
• This can be used to modify the value pointed to by ptr.

Examples:

int arr[5] = {1, 2, 3, 4, 5};
int *ptr = arr;

printf("%d ", *ptr++); // Prints 1 and increments ptr to the second element
printf("%d ", *++ptr); // Increments ptr to the third element and prints 3
printf("%d\n", ++*ptr); // Increments the value at the third element and prints 4

Output:

1 3 4

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