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How is memory allocated to arrays?
It depends where the array is declared and whether or not it is fixed-length or variable-length. The only thing all arrays have in common is that the memory is allocated contiguously. Fixed length arrays are arrays where the length is known at compile time while variable length arrays have unknown length and are allocated at runtime. Fixed-length arrays can be allocated statically, on the call stack (local memory) or on the heap (the free store) while variable length arrays must always be allocated on heap. Fixed-length arrays should use a constant variable to refer to the array length consistently while variable-length arrays should use a (mutable) variable. Arrays allocated on the heap must also use a pointer variable to keep track of the start address. The array (or pointer) and its length should always be declared in the same scope. Storing both in a data structure makes it easier to keep track of the array and its length. Static arrays are always fixed length and are allocated at load-time, before entry to the main function (even if declared in the main function or in another function entirely). The memory remains allocated until the program terminates. If there is insufficient memory available, the program itself will fail to load. It is recommended you use static memory sparingly and avoid the use of globals whenever possible. Local arrays are also fixed length but are allocated on the call stack at runtime as and when they come into scope. The memory is released automatically when the array falls from scope. The stack is fixed-length and therefore has limited capacity, so local arrays should be used sparingly. Variable length arrays and fixed-length arrays allocated on the heap are allocated and released manually (programmatically) at runtime. It is the programmer's responsibility to keep track of the array's start address. If there is insufficient memory available, it is the programmer's responsibility to handle the exception. Examples: // Fixed-length array at global scope // Note that all globals are implicitly static: const int a=10; int A[a]; // static array of 10 integers // Fixed-length array at file scope // Note that all file scope variables are explicitly static: static const int b=20; static int B[b]; // static array of 20 integers // Fixed-length arrays at function scope: void f () { const int size=100; static int C[size]; // static array of 100 integers (allocated at load-time) int D[size]; // local array of 100 integers (allocated when f comes into scope) int* E = malloc (size * sizeof (int)); // heap array of 100 integers // Note: if E is NULL, the allocation failed! // ...use arrays... free (E); // release the allocation before E falls from scope! E = NULL; // good housekeeping! } // D is released here // C, D and E will fall from scope here, however C is not released // Variable-length arrays at function scope: void g (const int n) { int* F = malloc (var * sizeof (int)); // heap array of n integers // ...use array... free (F); F = NULL; } // F falls from scope here.
What is the purpose of using arrays in C language?
The purpose of using arrays in C is to store multiple values in one variable. Then you can make programs that use arrays like lists, printing values from multiple arrays into one line. It take memory in continues block then we can know memory location easily. We can retrieve data quickly.
What is maximum length of variable in c?
The maximum length of a variable is dependent on the platform. In a 32 bit platform, this might be 4 bytes, although the compiler and run-time library might support 64 bit, or 8 byte variables. In a 64 bit platform, the length might be 8 bytes.(Arrays, strings, structures, classes, etc. are aggregated types, not scalar types, so they don't count in this answer.)
How can you make a array with the number 16?
If you mean how do you create an array with 16 elements, there are two ways: int a[16]; /* fixed size array of 16 integer elements */ int* b = malloc(16*sizeof(int)); /* variable length array with (initially) 16 integer elements */ Remember that variable length arrays allocated on the heap must be released as soon as they are no longer required: free (b); b=NULL;
What is C99?
The ISO C standard that came into being in 1999.
