What is tunable array?

Answer 1

Arrays are the cheapest data structures, without much overhead compare to other data structures. Basically in array, we have four types i.e

1. Static array - array size known at compile time.

// example code snippet:

char array[10];

2. Dynamic array - array size known at begging of execution time.

//example code snippet:

char *array;

int num_elements;

//Dynamic memory allocation using malloc library call which in turn uses "brk" // or "sbrk" system call under unix

array = (char *)malloc (num_elements * sizeof(char));

3. Stretchable array- array size can be stretched(modified) during execution time.

//example code snippet.

char *array;

int num_elements;

array = (char *)malloc (num_elements * sizeof(char));

//Modify the memory allocation during execution time using realloc library call

array = realloc (array, new_value);

4. Tunable array- array size known at link time.

Suppose consider you have one object file called sample.o(compiled sample.c)

and header file called sample.h.

ISV's (Independent software vendors) usually won't provide you the source code(In case of proprietary software), instead they will provide you the object file and one corresponding header file which contains some symbolic literals (some # define constants). so that you can change the symbolic literals in header file which takes necessary action when you compile both file together.

//example snippet code:

In sample.c

char arr[MAX_SIZE];

In sample.h

# define MAX_SIZE

Suppose now if you change the symbolic literal "MAX_SIZE"in header file sample.h that will affect the size of the array arr at link time.

Basically static array's are fall under the category of "Static Memory allocation" and remaining all will fall under "Dynamic Memory allocation".