Laboratory Manual
EEL 3801
Lab #7
Laboratory Assignment #7
EEL 3801 Introduction to Computer Engineering
Topic: Pointers, Dynamic Memory, Pass by Reference, and Arrays.
Turn in: .CPP file with screen output.
Pointers, Dynamic Memory, Pass by Reference, and Arrays
A pointer variable has the capability of holding an address. A pointer is the same thing as an
address you have already seen in assembly language. It refers to the number of bytes the data is
offset from the beginning of the segment. It may also refer to the segment as well as the offset. It
depends on the model that you are using. Using an *, the dereference operator, in front of a
pointer means that you are referring to the contents pointed to by the pointer and not the pointer
itself. The &, called the address operator, in front of a variable means that you are referring to
the address of the variable not it's contents. This is much like the offset and seg directives in
assembly language.
Example
int X, *P; // X is declared as an integer and P as a pointer
// capable of holding the address of an integer.
P = &X; // P points to X or it contains the address of X
X = 5; // X gets 5.
*P = 6; // X gets 6. P stays with the address of X
P = 7; // P gets 7. X stays with 6
Pointers are used for a variety of functions. The next three sections are common examples of the
many uses of pointers.
1. Dynamic Memory
Some of the more popular computer platforms support dynamic memory allocation. This is
where the program asks the operating system for a block of memory during execution. The
following line of code allocates sufficient memory to implement an integer. Note the new
function returns the address of the newly allocated memory so it must be received by a pointer
variable.
int * Pnt = new int;
To give the memory back to the operating system you use the delete function. The following
returns the memory back to the operating system.
delete Pnt;
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