In C, a string is an array of characters terminated by a null character '\0'. There is no built-in string type - strings are always char arrays.
// String declaration and initialization
char name[10] = "Alice"; // stored as: A l i c e \0 _ _ _ _
char name[] = "Alice"; // size inferred: 6 bytes (5 chars + \0)
char name[] = {'A','l','i','c','e','\0'}; // explicit null terminator
// String literal (read-only pointer)
char *msg = "Hello"; // pointer to string literalThe <string.h> header provides many useful string manipulation functions:
| Function | Description | Example |
|---|---|---|
strlen(s) | Returns length of string (excluding \0) | strlen("hello") -> 5 |
strcpy(dest, src) | Copies src into dest | strcpy(a, "hi") |
strncpy(dest, src, n) | Copies at most n characters | Safer version of strcpy |
strcat(dest, src) | Appends src to end of dest | strcat(a, " world") |
strncat(dest, src, n) | Appends at most n characters | Safer version of strcat |
strcmp(s1, s2) | Compares two strings; 0 if equal | strcmp("abc","abc") -> 0 |
strncmp(s1, s2, n) | Compares first n characters | Safer version of strcmp |
strchr(s, c) | Finds first occurrence of char c | strchr("hello",'l') |
strstr(s, sub) | Finds first occurrence of substring | strstr("hello","ell") |
strtok(s, delim) | Splits string by delimiter | strtok(s, ",") |
sprintf(buf, fmt, ...) | Writes formatted string to buffer | sprintf(buf, "%d", 42) |
sscanf(s, fmt, ...) | Reads formatted data from string | sscanf("42", "%d", &n) |
#include <stdio.h>
#include <string.h>
int main() {
char name[] = "Alice";
// Print string
printf("Name: %s\n", name);
printf("Length: %zu\n", strlen(name)); // 5
// Access individual characters
printf("Characters: ");
for (int i = 0; name[i] != '\0'; i++) {
printf("%c ", name[i]);
}
printf("\n");
// Null terminator
printf("name[5] = %d (null char)\n", name[5]); // 0
// Reading string with fgets (safer than scanf or gets)
char input[100];
printf("Enter your name: ");
fgets(input, sizeof(input), stdin);
// Remove trailing newline that fgets includes
input[strcspn(input, "\n")] = '\0';
printf("Hello, %s!\n", input);
return 0;
}#include <stdio.h>
#include <string.h>
int main() {
char s1[50] = "Hello";
char s2[] = "World";
char s3[50];
// strlen
printf("strlen(\"%s\") = %zu\n", s1, strlen(s1)); // 5
// strcpy
strcpy(s3, s1);
printf("strcpy: s3 = \"%s\"\n", s3); // Hello
// strcat
strcat(s1, " ");
strcat(s1, s2);
printf("strcat: s1 = \"%s\"\n", s1); // Hello World
// strcmp
int cmp = strcmp("apple", "banana");
printf("strcmp(\"apple\",\"banana\") = %d\n", cmp); // negative (a < b)
printf("strcmp(\"abc\",\"abc\") = %d\n", strcmp("abc","abc")); // 0
// strchr - find first occurrence of character
char *pos = strchr("Hello World", 'W');
if (pos) printf("strchr found 'W' at: \"%s\"\n", pos); // World
// strstr - find substring
char *sub = strstr("Hello World", "World");
if (sub) printf("strstr found: \"%s\"\n", sub); // World
return 0;
}#include <stdio.h>
#include <string.h>
void reverseString(char str[]) {
int len = strlen(str);
for (int i = 0; i < len / 2; i++) {
char temp = str[i];
str[i] = str[len - 1 - i];
str[len - 1 - i] = temp;
}
}
int isPalindrome(char str[]) {
int len = strlen(str);
for (int i = 0; i < len / 2; i++) {
if (str[i] != str[len - 1 - i]) return 0;
}
return 1;
}
int main() {
char s1[] = "Hello";
reverseString(s1);
printf("Reversed: %s\n", s1); // olleH
char words[][20] = {"racecar", "hello", "madam", "world"};
for (int i = 0; i < 4; i++) {
printf("\"%s\" is %s\n", words[i],
isPalindrome(words[i]) ? "a palindrome" : "not a palindrome");
}
return 0;
}
/*
Reversed: olleH
"racecar" is a palindrome
"hello" is not a palindrome
"madam" is a palindrome
"world" is not a palindrome
*/Explore 500+ free tutorials across 20+ languages and frameworks.