Why

• You can't define variable legth arrays.

      void f(unsigned int x) {
          char buf[strlen(str) + 1];
          long array[x];
      }
  

• You can't return an auto generated array.

      long * g() {
          long array[1024];
          return(array);
      }
  

• It is better to return what you need than to try and guess what is sufficient.

• Syntax:

      sizeof(object);
  
      sizeof(type name);
  

• Takes an object or object type as an argument.
• Returns a value, which is an unsigned integer type size_t
• Always returns 1 for type char.
• The return value represents the size of the object compared to a char.
• The return value of the sizeof a struct may be bigger than it's components.