take array length from user and create array in c code example

Example 1: size of an array c

int a[20];
int length;
length = sizeof(a) / sizeof(int);

Example 2: array length c

int prices[5] = { 1, 2, 3, 4, 5 };

int size = sizeof prices / sizeof prices[0];

printf("%u", size); /* 5 */