C Programming Pointers PDF

CST8234 – C Programming Pointers  Learning Outcomes ❖ Memory Allocation - Functions ❖ Understanding Pointers ❖ Pointer Arithmetic ❖ Function Parameter Passing ❖ Multidimensional Arrays 2  Memory Allocation Functions (1/4) The standard library pro...

CST8234 – C Programming Pointers  Learning Outcomes ❖ Memory Allocation - Functions ❖ Understanding Pointers ❖ Pointer Arithmetic ❖ Function Parameter Passing ❖ Multidimensional Arrays 2  Memory Allocation Functions (1/4) The standard library provides several functions for this purpose. ❑ malloc(): Allocates a specified number of bytes of memory and returns a pointer to the beginning of the block. #include void *malloc(size_t size); Parameters: size – the number of bytes of allocate Returns: A pointer to the allocated memory, or NULL if the allocation fails. int *arr = (int *)malloc(5 * sizeof(int)); if (arr == NULL) { } 3  Memory Allocation Functions (2/4) ❑ calloc(): Allocates a specified number of bytes of memory and returns a pointer to the beginning of the block. It also initializes all memory elements to a value ‘zero’. #include void *calloc(size_t num, size_t size); Parameters: num - number of elements to allocate and size – size of each element Returns: A pointer to the allocated memory, or NULL if the allocation fails. int *arr = (int *)calloc(5, sizeof(int)); if (arr == NULL) { } 4  Memory Allocation Functions (3/4) ❑ realloc(): Changes the size of previously allocated memory block. It can also be used to extend or reduce the size of the memory block. #include void *realloc(void *ptr, size_t size); Parameters: ptr - pointer to the previously allocated memory block and size – new size in bytes Returns: A pointer to the newly allocated memory, which may be the same as ptr, or NULL if the reallocation fails. arr = (int *)realloc(arr, 10 * sizeof(int)); if (arr == NULL) { } 5  Memory Allocation Functions (4/4) ❑ free(): Deallocates memory that was previously allocated. It is important to free any dynamically allocated memory to avoid memory leaks. #include void free(void *ptr); Parameters: ptr - pointer to the memory to be freed. Returns: Nothing. arr = (int *)realloc(arr, 10 * sizeof(int)); if (arr == NULL) { } 6  Pointers ❑ C pointers are a powerful feature that allows you to directly manipulate memory addresses. ❑ Definition: A pointer is a variable that stores the address of another variable. The type of pointer corresponds to the type of variable it points to (e.g., char*, int*) ❑ Declaration: To declare a pointer, you use the asterisk (*). int *ptr; ❑ Initialization: You can initialize a pointer to point to a variable: int var = 5; int *ptr = &var; ❑ Dereferencing: You can access the value stored at the address the pointer points to by dereferencing it with the asterisk: int value = *ptr; 7  Pointers int value = 5; int* address = &value; printf("the value is %d\n", value);