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C Aptitude Questions
Posted Date: 05 Mar 2008 Resource Type: Articles/Knowledge Sharing Category: Placement Papers
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Posted By: Girish Patil Member Level: Diamond
Rating:  Points: 5
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Strings
In C language Strings are defined as an array of characters or a pointer to a portion of memory containing ASCII characters. A string in C is a sequence of zero or more characters followed by a NULL '\0' character:
It is important to preserve the NULL terminating character as it is how C defines and manages variable length strings. All the C standard library functions require this for successful operation.
All the string handling functions are prototyped in: string.h or stdio.h standard header file. So while using any string related function, don't forget to include either stdio.h or string.h. May be your compiler differs so please check before going ahead.
If you were to have an array of characters WITHOUT the null character as the last element, you'd have an ordinary character array, rather than a string constant.
String constants have double quote marks around them, and can be assigned to char pointers as shown below. Alternatively, you can assign a string constant to a char array - either with no size specified, or you can specify a size, but don't forget to leave a space for the null character!
char *string_1 = "Hello";
char string_2[] = "Hello";
char string_3[6] = "Hello";
Reading and Writing Strings:
One possible way to read in a string is by using scanf. However, the problem with this, is that if you were to enter a string which contains one or more spaces, scanf would finish reading when it reaches a space, or if return is pressed. As a result, the string would get cut off. So we could use the gets function
A gets takes just one argument - a char pointer, or the name of a char array, but don't forget to declare the array / pointer variable first! What's more, is that it automatically prints out a newline character, making the output a little neater.
A puts function is similar to gets function in the way that it takes one argument - a char pointer. This also automatically adds a newline character after printing out the string. Sometimes this can be a disadvantage, so printf could be used instead.
#include
int main() {
char array1[50];
char *array2;
printf("Now enter another string less than 50");
printf(" characters with spaces: \n");
gets(array1);
printf("\nYou entered: ");
puts(array1);
printf("\nTry entering a string less than 50");
printf(" characters, with spaces: \n");
scanf("%s", array2);
printf("\nYou entered: %s\n", array2);
return 0;
}
This will produce following result:
Now enter another string less than 50 characters with spaces:
hello world
You entered: hello world
Try entering a string less than 50 characters, with spaces:
hello world
You entered: hello
String Manipulation Functions:
char *strcpy (char *dest, char *src);
Copy src string into dest string.
char *strncpy(char *string1, char *string2, int n);
Copy first n characters of string2 to stringl .
int strcmp(char *string1, char *string2);
Compare string1 and string2 to determine alphabetic order.
int strncmp(char *string1, char *string2, int n);
Compare first n characters of two strings.
int strlen(char *string);
Determine the length of a string.
char *strcat(char *dest, const char *src);
Concatenate string src to the string dest.
char *strncat(char *dest, const char *src, int n);
Concatenate n characters from string src to the string dest.
char *strchr(char *string, int c);
Find first occurrence of character c in string.
char *strrchr(char *string, int c);
Find last occurrence of character c in string.
char *strstr(char *string2, char string*1);
Find first occurrence of string string1 in string2.
char *strtok(char *s, const char *delim) ;
Parse the string s into tokens using delim as delimiter.
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