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

Pointer Expressions: Navigating ptr , ptr, and *ptr

These pointer expressions are often encountered in C programming and can be tricky to understand. Here's a detailed explanation:

1. *ptr

• Precedence: * (indirection) has higher precedence than (increment).
• Expression Value: Evaluates to the value pointed to by ptr before incrementing.
• Side Effect: Increments ptr by one memory unit.

Example:

int a = 5;
int *ptr = &a;

*ptr++; // evaluates to 5, then increments ptr to point to the next integer

2. * ptr

• Precedence: (increment) and * (indirection) have equal precedence.
• Expression Value: Evaluates to the value pointed to by ptr after incrementing.
• Side Effect: Increments ptr by one memory unit.

Example:

int a = 5;
int *ptr = &a;

*++ptr; // evaluates to 6 (a++) and increments ptr

3. *ptr

• Precedence: (increment) and * (indirection) have equal precedence.
• Associativity: Right-to-left.
• Expression Value: Increments the value pointed to by ptr.
• Side Effect: None.

Example:

int a = 5;
int *ptr = &a;

++*ptr; // increments a to 6

4. (*ptr)

• Precedence: Parentheses override precedence rules.
• Expression Value: Evaluates to the dereferenced value at ptr before incrementing.
• Side Effect: Increments the dereferenced value.

Example:

int a = 5;
int *ptr = &a;

(*ptr)++; // evaluates to 5, then increments *ptr to 6

Note that ptr , ptr, and ptr can crash if ptr is an array identifier, while (ptr) can crash if ptr points to a string literal.

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