Strings
What Are Strings in C?
In C, strings are sequences of characters such as letters, numbers, or symbols used to represent text. Unlike other languages, strings in C are implemented as arrays of characters. Each character in a string is stored in a specific position within this array.
A unique feature of strings in C is the inclusion of a special character at the end of the array called the ‘null terminator,’ represented by \0
. This null terminator signals the end of the string to the computer.
For example, the string “Hello” in C is stored in memory as “Hello\0”.
VIDEO CREDIT:- CODE WITH HARRY
How to Create Strings in C
Creating strings in C involves using arrays of characters. Here are a few ways to create and manipulate strings in C:
- Using Character Arrays: You can create a string by defining a character array and initializing it with a sequence of characters.
char greeting[] = "Hello";
In this example, the array
greeting
contains six characters: ‘H’, ‘e’, ‘l’, ‘l’, ‘o’, and the null terminator\0
. - Using Pointers: You can also create a string using a pointer to a character.
char *greeting = "Hello";
Here,
greeting
points to a string literal stored in read-only memory, which is automatically null-terminated. - Manual Initialization: You can manually initialize the character array with each character, including the null terminator.
char greeting[6] = {'H', 'e', 'l', 'l', 'o', '\0'};
This explicitly sets each character in the array, ensuring that the string is properly null-terminated.
Important Considerations
- Null Terminator: Always ensure that your strings are null-terminated. Without the
\0
, functions that operate on strings (such asstrlen
andstrcpy
) will not work correctly and might read beyond the array boundaries, leading to undefined behavior. - String Length: When declaring a character array for a string, make sure it is large enough to hold all the characters plus the null terminator. For example, to store “Hello”, you need an array of at least 6 characters.
- Modifying Strings: If you need to modify the string, use character arrays rather than pointers to string literals, as string literals are stored in read-only memory.
Example: Creating and Printing a String
Here is a complete example demonstrating how to create and print a string in C:
int main() {
char greeting[] = "Hello, World!";
printf("%s\n", greeting);
return 0;
}
In this example, the greeting
array is initialized with the string “Hello, World!”, and printf
is used to print the string to the console. The %s
format specifier in printf
is used for strings.
How to Manipulate Strings in C
Manipulating strings in C involves various operations like copying, concatenating, comparing, and finding the length of strings. Here are some common string manipulation functions provided by the C standard library:
- Copying Strings:
strcpy
andstrncpy
strcpy
: Copies one string into another.
int main() {
char source[] = "Hello, World!";
char destination[50];
strcpy(destination, source);
printf("Copied string: %s\n", destination);
return 0;
}
strncpy
: Copies up to a specified number of characters.
int main() {
char source[] = "Hello, World!";
char destination[50];
strncpy(destination, source, 5);
destination[5] = '\0';
// Ensure null termination
printf("Copied string: %s\n", destination);
return 0;
}
- Concatenating Strings:
strcat
andstrncat
strcat
: Appends one string to the end of another.
int main() {
char str1[50] = "Hello";
char str2[] = ", World!";strcat(str1, str2);
printf("Concatenated string: %s\n", str1);
return 0;
}
strncat
: Appends up to a specified number of characters from one string to another.
int main() {
char str1[50] = "Hello";
char str2[] = ", World!";strncat(str1, str2, 5);
printf("Concatenated string: %s\n", str1);
return 0;
}
- Comparing Strings:
strcmp
andstrncmp
strcmp
: Compares two strings lexicographically.
int main() {
char str1[] = "Hello";
char str2[] = "World";
if (strcmp(str1, str2) == 0)
{
printf("Strings are equal.\n");
} else {
printf("Strings are not equal.\n");
}
return 0;
}
strncmp
: Compares up to a specified number of characters of two strings.
int main() {
char str1[] = "Hello";
char str2[] = "Helium";if (strncmp(str1, str2, 3) == 0) {
printf("First 3 characters are equal.\n");
} else {
printf("First 3 characters are not equal.\n");
}
return 0;
}
- Finding String Length:
strlen
strlen
: Returns the length of a string (excluding the null terminator).
int main() {
char str[] = "Hello, World!";
printf("Length of string: %zu\n", strlen(str));
return 0;
}
Example: Combining String Manipulation Functions
Here is an example that combines several string manipulation functions:
int main() {
char str1[50] = "Hello";
char str2[] = ", World!";
char str3[50];
// Copying str1 to str3
strcpy(str3, str1);
printf("Copied str1 to str3: %s\n", str3);
// Concatenating str2 to str3
strcat(str3, str2);
printf("Concatenated str2 to str3: %s\n", str3);
// Comparing str1 and str3
if (strcmp(str1, str3) == 0) {
printf("str1 and str3 are equal.\n");
} else {
printf("str1 and str3 are not equal.\n");
}
// Finding the length of str3
printf("Length of str3: %zu\n",
strlen(str3));
return 0;
}
This program demonstrates copying, concatenating, comparing, and finding the length of strings using the appropriate standard library functions.
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