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Questions and Answers
What does the strlen function return?
What does the strlen function return?
- The total size of the memory allocated for the string including the null character.
- The number of characters in the string including the null character.
- The number of characters in the string excluding the null character. (correct)
- The number of bytes allocated for the entire string including the null character.
What happens if the new operator fails to allocate memory?
What happens if the new operator fails to allocate memory?
- It returns a NULL pointer. (correct)
- It returns an integer indicating the type of error.
- It returns a pointer to the allocated memory.
- It throws an exception.
Which task does the strcpy function perform?
Which task does the strcpy function perform?
- Copies only the non-null characters from the source string.
- Copies characters up to the last non-null character.
- Copies the source string to the destination, including the null character. (correct)
- Copies the source string to the destination, excluding the null character.
In pointer arithmetic, adding an integer to a pointer does what?
In pointer arithmetic, adding an integer to a pointer does what?
Why is it important to manage dynamic memory allocation carefully?
Why is it important to manage dynamic memory allocation carefully?
What is the expected outcome after using the strlen function on an empty string?
What is the expected outcome after using the strlen function on an empty string?
If a programmer tries to copy more characters than allocated in the destination string with strcpy, what is likely to happen?
If a programmer tries to copy more characters than allocated in the destination string with strcpy, what is likely to happen?
If an int is represented by 4 bytes, what does adding 1 to an int pointer do?
If an int is represented by 4 bytes, what does adding 1 to an int pointer do?
What is the correct way to dynamically allocate an array of characters to hold a string of length n using C++?
What is the correct way to dynamically allocate an array of characters to hold a string of length n using C++?
What is pointer arithmetic often used for in programming?
What is pointer arithmetic often used for in programming?
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Study Notes
Pointers
- A pointer is an address of a memory location, allowing indirect access to data.
- Pointer variables need to be defined for specific data types, e.g.,
int *ptr1;for integers andchar *ptr2;for characters. - The value of a pointer variable is the address of the variable it points to, such as
ptr1 = #, wherenumis an integer variable. - The address operator
&retrieves the memory address of a variable, while the dereference operator*accesses the contents at that address, e.g.,*ptr1retrieves the value ofnum. - Pointer types must match the type of the data they point to, except for
void*, which can point to any data type. - Pointers can be cast to different types, such as converting an
int*to achar*via(char*) ptr1.
Null Pointers
- The null pointer (value 0) is used for initializing pointers and marking the end of pointer-based structures like linked lists.
Dynamic Memory
- The heap is used for dynamically allocating memory during program execution, in contrast to the program stack which is static.
- The
newoperator allocates memory on the heap for a specified type and returns a pointer to it, e.g.,int *ptr = new int;. - Memory allocated on the heap persists beyond the scope of the function that created it and must be manually released using the
deleteoperator. - Functions like
strlenandstrcpyhandle string operations;strlencounts characters up to the null terminator whilestrcpycopies strings including the null character. - Dynamic memory can become exhausted if not managed properly, leading
newto return 0 when it fails to allocate.
Pointer Arithmetic
- Pointer arithmetic allows adding or subtracting integers to/from pointers, affecting the pointer based on the size of the data type pointed to.
- For example, adding 1 to an integer pointer shifts the pointer by the size of an integer (e.g., 4 bytes).
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