Question

Please tell me why the following code runs even on a strict C-99 compiler:

#include <stdio.h>
int main()
{
    int n;
    scanf("%d",&n);
    int a[n];
    a[1]=10;
    a[2]=5;
    printf("%d %d",a[1],a[2]);
}

The variable declaration must occur before any other statements in C right? If we so want a dynamically allocated array, we have to use memory allocation functions like malloc() but how come it is taking and input integer and allocating that sized array?

Answer 1

This is known as a variable-length array, and is supported by the C99 standard.
This does not work in C89 or any version of C++.