String basics

Learn C strings with char arrays and the null terminator.

A string is a char array

C has no separate string type. A string is a char array that ends with a null character ('\0'). This character tells functions where the string ends.

char name[5] = {'A', 'l', 'i', '\0'};
printf("%s", name);  /* prints Ali */

Even though the array has 4 slots, '\0' takes one; so a 3-letter name needs a 4-element array. The %s format specifier prints characters up to '\0'.

Printing a string with %s

The printf function prints a char array as a string using the %s format specifier. It reads up to '\0' and ignores the rest.

char city[] = "Berlin";
printf("City: %s\n", city);
/* City: Berlin */

If the array has data after '\0', %s does not print it. So sizing the array and placing the terminator correctly matter.

Exercise First string: print a name from a char array

Declare a char array holding 'A', 'l', 'i' followed by '\0'. Print it with printf and %s; the output should be Ali.

Show example solution

#include <stdio.h>

int main(void) {
    char name[] = {'A', 'l', 'i', '\0'};
    printf("%s\n", name);
    return 0;
}

Test yourself

How many elements does a char array need to hold the 3-letter string "Ali"?
```
char name[?] = "Ali";
```
- 2
- 3
- 5
- 4
Show answer

4 — You need room for 3 letters plus the null character; 4 elements total.

Null terminator in a char array

char end = ____;  /* string terminator */

Show answer

char end = '\0';  /* string terminator */

Match the string concepts

char

character type
\0

string terminator
%s

string format specifier
printf

output function

Next lesson: String literals

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