HP C A.06.05 Reference Manual

Program Organization

Declarations

Chapter 2 21

Using typedefs for Arrays

The following two examples illustrate what can happen when you mix pointers and typedefs

that represent arrays. The problem with the program on the left is that ptr points to an array

of 80 chars, rather than a single element of a char array. Because of scaling in pointer

arithmetic, the increment operator adds 80 bytes, not one byte, to ptr.

Name Spaces

All identiﬁers (names) in a program fall into one of four name spaces. Names in different

name spaces never interfere with each other. That is, you can use the same name for an object

in each of the four name spaces without these names affecting one another. Table 2-2 lists the

four name spaces:

Table 2-1 Mixing Pointers and Typedefs

Wrong Right

typedef char STR[80];

STR string, *ptr;

main()

{

ptr = string;

printf("ptr = %d\n", ptr);

ptr++;

printf("ptr = %d\n", ptr);

}

*** Run-Time Results ***

ptr = 3997696

ptr = 3997776

typedef char STR[80];

STR string;

char *ptr;

main()

{

ptr = string;

printf("ptr = %d\n", ptr);

ptr++;

printf("ptr = %d\n", ptr);

}

*** Run-Time Results ***

ptr = 3997696

ptr = 3997697

Table 2-2 Name Spaces

Name Spaces Description

Structure, Union,

and Enumeration