What is malloc doing in this code?

Question

Could you explain following code?

str = (char *) malloc (sizeof(char) * (num+1));

1. What is malloc doing here?

Answer 1

malloc allocates an array of char (in this case) on the heap.

array will be num+1 long, but the longest string it can possibly hold is 'num' long, because string in C need a ending null-byte.