Review of Pointers and Addresses

• C has a simple memory model. Blocks of memory are
  organized as a sequence of bytes which can be manipulated
  individually or in contiguous groups.
• Each byte of memory has an address.

An addresses is stored in a pointer.

• Each datatype requires one or more bytes to store it.
  Typically a character requires one byte, an integer requires
  2 or 4 bytes, a double usually take 8 bytes, and so on. It
  follows that not every byte address is a legitimate address
  of a data object.

Consider how we exchange two values in memory. For the
quantities a and b, we would simply write
float a, b;
float t;

t = a;
a = b;
b = t;

• However, if we want to do the same thing inside a
  procedure we would have to pass the addresses of aand bas
  actual parameters, as follows

swap( &a, &b );

January 26, 1998

Page2

JH/TM