C Strings in C Programming

Introduction

Unlike many modern languages, C has no built-in string type. A string is a character array terminated by a null character ('\0', ASCII 0). This is one of the most important concepts in C programming.

Declaring Strings

char name[20] = "Kumar";       /* 5 chars + '\0' */
char greeting[] = "Hello";     /* size inferred: 6 bytes */
char ch = 'A';                 /* single character, not a string */

The compiler automatically adds '\0' at the end of string literals.

Reading and Printing Strings

#include <stdio.h>

int main(void) {
    char name[50];

    printf("Enter your name: ");
    scanf("%49s", name);

    printf("Hello, %s!\n", name);
    return 0;
}

Use %s with printf. For safer input with spaces, use fgets(name, sizeof(name), stdin).

String Length with strlen

From <string.h>:

#include <stdio.h>
#include <string.h>

int main(void) {
    char word[] = "Hello";
    printf("Length: %zu\n", strlen(word));
    return 0;
}

Sample Output

Length: 5

strlen counts characters before the null terminator — it does not include '\0'.

Common String Functions

Comparing Strings

Never use == to compare string contents — that compares addresses. Use strcmp:

if (strcmp(name, "admin") == 0)
    printf("Welcome, admin\n");

Manual String Traversal

char str[] = "C language";
int i = 0;
while (str[i] != '\0') {
    printf("%c", str[i]);
    i++;
}

Best Practices

• Always leave room for '\0' — a 10-char string needs char s[11].
• Use strncpy / strncat or snprintf when buffer size is limited.
• Prefer const char* for read-only string parameters.
• Initialize char arrays or set first byte to '\0' before strcat.

Common Mistakes

• Buffer overflow — writing past array bounds with strcpy.
• Forgetting null terminator when building strings manually.
• Comparing strings with == instead of strcmp.
• Using %s in scanf without width limit.

Related Programs

Explore our String Example Programs including strlen, strrev, strcpy and concatenation examples.