Sams Teach Yourself C in 21 Days

Implementing Structures, Unions, and TypeDefs 267

11

char *p_message;

p_message = “Teach Yourself C In 21 Days”;

You can do the same thing with pointers to type charthat are structure members:

struct msg {

char *p1;

char *p2;

} myptrs;

myptrs.p1 = “Teach Yourself C In 21 Days”;

myptrs.p2 = “By SAMS Publishing”;

Figure 11.4 illustrates the result of executing these statements. Each pointer member of

the structure points to the first byte of a string, stored elsewhere in memory. Contrast this

with Figure 11.3, which shows how data is stored in a structure that contains arrays of

typechar.

FIGURE11.4

A structure that con-

tains pointers to type

char.

1008

2252

myptrs

myptrs.p1

myptrs.p2

Teach Yourself C In 21 Days\0

By SAMS Publishing\0

1008 1009....

2252 2253....

You can use pointer structure members anywhere a pointer can be used. For example, to

print the pointed-to strings, you would write

printf(“%s %s”, myptrs.p1, myptrs.p2);

What’s the difference between using an array of type charas a structure member and

using a pointer to type char? These are both methods for “storing” a string in a structure,

as shown here in the structure msg, which uses both methods:

struct msg

{

char p1[30];

char *p2; /* caution: uninitialized */

} myptrs;

Recall that an array name without brackets is a pointer to the first array element.

Therefore, you can use these two structure members in similar fashion (note that p2

should be initialized before you copy a value to it):

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