How can you check if a pointer is NULL in C?

How can you check if a pointer is NULL in C?

• A. By initializing it before use
• B. By evaluating it in a conditional statement
• C. By printing its value directly
• D. By using the sizeof operator

Answer: (B)

In C, to check if a pointer is NULL, evaluating it in a conditional statement is the most effective method. When you use a pointer in a condition, such as an `if` statement, it evaluates whether the pointer is pointing to a valid memory location or if it is NULL (which means it is not pointing anywhere). This evaluation directly translates to a Boolean check; if the pointer is NULL, the condition will be false, and if it points to a valid address, the condition will be true. Using a conditional statement provides a clear and direct way to control the flow of the program based on whether the pointer is NULL. For instance, you can manage resource allocation or execution of certain blocks of code only when the pointer is valid, thus preventing potential segmentation faults or dereferencing a NULL pointer which would lead to crashes. Other options do not perform the necessary checks. Initializing a pointer before use ensures it has a defined state, but does not check if it is NULL after initialization. Printing a pointer’s value displays its address or NULL, but it doesn’t evaluate its state for conditional execution. The sizeof operator is used for determining the size of data types in bytes and cannot check the state of a pointer at all.

In C, to check if a pointer is NULL, evaluating it in a conditional statement is the most effective method. When you use a pointer in a condition, such as an if statement, it evaluates whether the pointer is pointing to a valid memory location or if it is NULL (which means it is not pointing anywhere). This evaluation directly translates to a Boolean check; if the pointer is NULL, the condition will be false, and if it points to a valid address, the condition will be true.

Using a conditional statement provides a clear and direct way to control the flow of the program based on whether the pointer is NULL. For instance, you can manage resource allocation or execution of certain blocks of code only when the pointer is valid, thus preventing potential segmentation faults or dereferencing a NULL pointer which would lead to crashes.

Other options do not perform the necessary checks. Initializing a pointer before use ensures it has a defined state, but does not check if it is NULL after initialization. Printing a pointer’s value displays its address or NULL, but it doesn’t evaluate its state for conditional execution. The sizeof operator is used for determining the size of data types in bytes and cannot check the state of a pointer at all.