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/* Allocate space for an array with ten elements of type int. */
int *ptr = malloc(10 * sizeof (int));
if (ptr == NULL) { /* Memory could not be allocated, the program should handle the error here as appropriate. */ realloc It is often useful to be able to grow or shrink a block of memory. This can be done using realloc which returns a pointer to a memory region of the specified size, which contains the same data as the old region pointed to by ptr (truncated to the minimum of the old and new sizes). If realloc is unable to resize the memory region in-place, it allocates new storage, copies the required data, and frees the old pointer. If this allocation fails, realloc maintains the original pointer unaltered, and returns the null pointer value. The newly allocated region of memory is uninitialized (its contents are not predictable). The function prototype is void *realloc(void *pointer, size_t size);
Wiki User
∙ 16y ago
Wiki User
∙ 14y agoint arr[10]; When an array is declared as above, memory is allocated for the elements of the array when the program starts, and this memory remains allocated during the lifetime of the program. This is known as static array allocation. Hence we cannot increase size of statically allocated array.
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What is the difference between a fixed size array and a variable size array?
The obvious answer is that one has a constant size while the other does not. More specifically, a fixed-size array is one where the size is known at compile time and does not change at runtime. By contrast, the size of a variable-sized array may or may not be known at compile time but may change at runtime. We often refer to a variable-size array as being a dynamic array, however some people (myself included) incorrectly refer to a fixed-size array as being a static array. The misunderstanding largely comes from the fact that we often refer to the heap (or free store) as being dynamic memory because all dynamic variables are allocated there (including variable-size arrays). But the term dynamic array does not refer to the memory, it refers to the dynamic -- as in changeable -- nature of the array itself. By contrast, a fixed-size array is only deemed static if it is statically allocated, in which case it will be allocated in the program's data segment along with all other static variables, global variables and constants. But a local fixed-size array is allocated on the program's stack and is therefore, by definition, non-static. Moreover, you can allocate a fixed-size array on the heap!
Why would you use the array of pointers to pointers?
You would use an array of pointers to pointers whenever you wished to implement a dynamic multi-dimensional array of 3 or more dimensions. Every multi-dimensional array can ultimately be reduced to a one-dimensional array where each element is itself a one-dimensional array (an array of arrays). With fixed-size arrays, all elements can be allocated contiguously regardless of how many dimensions there are. Fixed size arrays can be allocated both statically (when the size is known at compile time) or dynamically (when the size is unknown at compile time). However with large arrays it is often necessary to divide the array into smaller subarrays each of which is allocated separately (non-contiguously with each other) and maintain a separate array of pointers to keep track of each of those subarrays. Although this consumes more memory than a contiguously-allocated array would, it has the added benefit in that each subarray need not be the same length, thus it can actually save memory overall. However, if we had several such arrays then we would need yet another array in order to keep track of them all, and this array would need to be an array of pointers to pointers.
When is memory allocated when declaring an array in C plus plus?
It depends how the array is declared (fixed size or variable size) and where it is declared (global scope or local scope). If the array is declared in global scope (outside a function) and is fixed size, it will be allocated in static memory. If it is variable size, the pointer is stored in static memory while the array itself is allocated on the heap. The pointer in static memory points to the start address of the array in heap memory. If the array is declared in local scope (inside a function) and is fixed size, it will be allocated on the stack in whichever thread the function was called. If it is variable size, the local pointer is stored on the stack while the array is allocated on the heap. The pointer will fall from scope when the function returns so the array must not be allowed to outlive the function in which the pointer is declared. If the array must outlive the function that allocates the array, the pointer must be declared at a higher scope in the call stack and must be passed by reference to or returned by value from the function that allocates the array. If you provide your own memory manager, however, an array may be allocated wherever the memory manager's memory pool is allocated, be it in static memory, the stack or the heap. A memory manager essentially allocates an array of bytes which you can then utilise as you see fit (the array of bytes will be allocated as per the previous description for arrays in general).
What is the term given to the memory allocation that takes place during run time rendering the resizing of an Array?
A reallocation. Note that whenever we reallocate an array, we increase the size of the current allocation if there is sufficient free memory beyond the current allocation or we allocate entirely new memory if there isn't. But when we reduce the size of an array, we simply release the redundant memory at the end of the array; we never allocate new memory. However, because the amount of memory being allocated has to either increase or reduce in size, both are termed a reallocation.
How can you accommodate faster devices on a network that implements sychronous time-division multiplexing?
Increase the number of blocks allocated to these devices Increase the size of the blocks allocated to all devices
What is the difference between a fixed size array and a variable size array?
The obvious answer is that one has a constant size while the other does not. More specifically, a fixed-size array is one where the size is known at compile time and does not change at runtime. By contrast, the size of a variable-sized array may or may not be known at compile time but may change at runtime. We often refer to a variable-size array as being a dynamic array, however some people (myself included) incorrectly refer to a fixed-size array as being a static array. The misunderstanding largely comes from the fact that we often refer to the heap (or free store) as being dynamic memory because all dynamic variables are allocated there (including variable-size arrays). But the term dynamic array does not refer to the memory, it refers to the dynamic -- as in changeable -- nature of the array itself. By contrast, a fixed-size array is only deemed static if it is statically allocated, in which case it will be allocated in the program's data segment along with all other static variables, global variables and constants. But a local fixed-size array is allocated on the program's stack and is therefore, by definition, non-static. Moreover, you can allocate a fixed-size array on the heap!
Why would you use the array of pointers to pointers?
You would use an array of pointers to pointers whenever you wished to implement a dynamic multi-dimensional array of 3 or more dimensions. Every multi-dimensional array can ultimately be reduced to a one-dimensional array where each element is itself a one-dimensional array (an array of arrays). With fixed-size arrays, all elements can be allocated contiguously regardless of how many dimensions there are. Fixed size arrays can be allocated both statically (when the size is known at compile time) or dynamically (when the size is unknown at compile time). However with large arrays it is often necessary to divide the array into smaller subarrays each of which is allocated separately (non-contiguously with each other) and maintain a separate array of pointers to keep track of each of those subarrays. Although this consumes more memory than a contiguously-allocated array would, it has the added benefit in that each subarray need not be the same length, thus it can actually save memory overall. However, if we had several such arrays then we would need yet another array in order to keep track of them all, and this array would need to be an array of pointers to pointers.
When is memory allocated when declaring an array in C plus plus?
It depends how the array is declared (fixed size or variable size) and where it is declared (global scope or local scope). If the array is declared in global scope (outside a function) and is fixed size, it will be allocated in static memory. If it is variable size, the pointer is stored in static memory while the array itself is allocated on the heap. The pointer in static memory points to the start address of the array in heap memory. If the array is declared in local scope (inside a function) and is fixed size, it will be allocated on the stack in whichever thread the function was called. If it is variable size, the local pointer is stored on the stack while the array is allocated on the heap. The pointer will fall from scope when the function returns so the array must not be allowed to outlive the function in which the pointer is declared. If the array must outlive the function that allocates the array, the pointer must be declared at a higher scope in the call stack and must be passed by reference to or returned by value from the function that allocates the array. If you provide your own memory manager, however, an array may be allocated wherever the memory manager's memory pool is allocated, be it in static memory, the stack or the heap. A memory manager essentially allocates an array of bytes which you can then utilise as you see fit (the array of bytes will be allocated as per the previous description for arrays in general).
What is the term given to the memory allocation that takes place during run time rendering the resizing of an Array?
A reallocation. Note that whenever we reallocate an array, we increase the size of the current allocation if there is sufficient free memory beyond the current allocation or we allocate entirely new memory if there isn't. But when we reduce the size of an array, we simply release the redundant memory at the end of the array; we never allocate new memory. However, because the amount of memory being allocated has to either increase or reduce in size, both are termed a reallocation.
How can you accommodate faster devices on a network that implements synchronous time-division multiplexing?
Increase the size of the blocks allocated to all devices Increase the number of blocks allocated to these devices
How can you accommodate faster devices on a network that implements sychronous time-division multiplexing?
Increase the number of blocks allocated to these devices Increase the size of the blocks allocated to all devices
The maximum number of records you might want to store in an array is defined as MAX When using 0 based indexing what index will reference the last allocated position of an array of size MAX?
If all elements of the array are in use then the last record is referred to as MAX-1. If you are using a count variable to remember how far into the array you are using then this variable will keep track of the last allocated value in the array.
Write a c program to determine the size of an array?
using sizeof operator the size of whole array can be calculated, then divide it with the zise of the datatype(E.g. for int =4, char =2....etc.) Example: #define Narray (sizeof(array)/sizeof(array[0]))
What will happen if you try to write to an array element larger than your array?
The results of that programming error is undefined. You must NEVER EVER write, or EVEN READ an array element beyond the allocated size of the array. Period.I would flunk a student that consistently did this, and I would fire a programmer that did the same.
Difference between array and union?
All the members of the structure can be accessed at once,where as in an union only one member can be used at a time. Another important difference is in the size allocated to a structure and an union. for eg: struct example { int integer; float floating_numbers; } the size allocated here is sizeof(int)+sizeof(float); where as in an union union example { int integer; float floating_numbers; } size allocated is the size of the highest member. so size is=sizeof(float);
What are the various applications of linked list and how it is differ from array as a data structure?
Linked lists can be expanded or reduced in size at any time in response to the needs of the program.Arrays are fixed in size when initially allocated and cannot change.
Sample program of single-dimentional array?
#include "stdio.h" #define SIZE 100; void main() { int array[SIZE], i, size; printf("\nEnter the Size off Array :- "); scanf("%d", &size); printf("\nEnter the Elements of Array :- ")' for(i = 0; i < size; i++) scanf("%d", &array[i]; printf("\nThe Elements of entered Array :- "); for(i = 0; i < size; i++) printf("%7d", array[i]); }
