Character Arrays
A string constant , such as
"I am a string"
is an array of characters. It is represented internally in C by the ASCII characters in the string, i.e., “I”, blank, “a”, “m”,…or the above string, and terminated by the special null character “\0” so programs can find the end of the string.
String constants are often used in making the output of code intelligible using printf:
printf("Hello, world\n");
printf("The value of a is: %f\n", a);
String constants can be associated with variables. C provides the character type variable, which can contain one character (1 byte) at a time. A character string is stored in an array of character type, one ASCII character per location.
Never forget that, since strings are conventionally terminated by the null character “\0”, we require one extra storage location in the array.
C does not provide any operator which manipulates entire strings at once. Strings are manipulated either via pointers or via special routines available from the standard string library string.h.
Using character pointers is relatively easy since the name of an array is a just a pointer to its first element. Consider the program given next:
#include<stdio.h>
void main()
{
char text_1[100], text_2[100], text_3[100];
char *ta, *tb;
int i;
/* set message to be an arrray */
/* of characters; initialize it */
/* to the constant string "..." */
/* let the compiler decide on */
/* its size by using [] */
char message[] = "Hello, I am a string; what are
you?";
printf("Original message: %s\n", message);
/* copy the message to text_1 */
i=0;
while ( (text_1[i] = message[i]) != '\0' )
i++;
printf("Text_1: %s\n", text_1);
/* use explicit pointer arithmetic */
ta=message;
tb=text_2;
while ( ( *tb++ = *ta++ ) != '\0' )
;
printf("Text_2: %s\n", text_2);
}
The output of the program will be as follows:
Original message: Hello, I am a string; what are you?
Text_1: Hello, I am a string; what are you?
Text_2: Hello, I am a string; what are you? |
The standard “string” library contains many useful functions to manipulate strings, which we will learn in the string section later.
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