CompuServe Thread

Scott, When you allocate memory for an array with malloc(), you cast the pointer which malloc() returns for you to the type that you require. For example, #define ARRAY_SIZE 1000L int *i_ptr; struct foobar *foo; /*defined somewhere else*/ i_ptr = (* int)malloc(ARRAY_SIZE * sizeof(int)); foo = (* struct foobar)malloc(ARRAY_SIZE * sizeof(struct foobar)); Under this example, i_ptr would be a pointer to an integer at the beginning of a block of memory long enough to hold 1000 integers. You can then treat this block as an array of 1000 integers. The value of the first element can be addressed as *i_ptr or as i_ptr[0]; the second element as *(i_ptr + 1) or as i_ptr[1]; and the last element as *(i_ptr + 999) or as i_ptr[999]. Variable foo would be a pointer to a foobar structure at the beginning of a block of memory long enough to hold 1000 such structures. You can treat this block as an array of 1000 foobar structures with the contents of the first element addressed as foo[0] or as *foo, the second element as *(foo + 1) or foo[1], etc. The compiler will scale the pointer according to the size of the data type the pointer points to. That's why you have to cast the return value from malloc() to the appropriate pointer type. BTW, you can use any integer type for the array subscripts, so if your array has more than 32K elements, you need to use a 32 bit integer. Darron