• Variable-length automatic arrays are allowed in C99, C90 mode.
• Variable length arrays is a feature where we can allocate an auto array (on stack) of variable size.

• C supports variable sized arrays from C99 standard. For example, the below program compiles and runs fine in C.

• In variable length arrays dimensions of the array can also be specified by an valid expression.
• Values to the arguments can be specified at run time.

/* Example-1 program for variable length array */

#include<stdio.h>
#include<conio.h>

void action(int);
main()
{
int n;
clrscr();
printf("\n Enter n value:");
scanf("%d",&n);
action(n);
}

void action(int n)
{
int i, a[n];
printf("\n Enter the array elements: ");
for(i=0; i<n; i++)
scanf("%d",&a[i]);
printf("\n The given array elements are: ");
for(i=0; i<n; i++)
printf("%d",a[i]);
}

• argc
• argv[]

• In real time application, it will happen to pass arguments to the main program itself.  These arguments are passed to the main () function while executing binary file from command line.