Oppiskele Declaring Character Arrays | Creating and Storing Strings

Definition

Definition:
A character array is a sequence of elements of type char stored contiguously in memory. In C, character arrays are commonly used to store strings, which are sequences of characters terminated by a special null character ('\0').

When you declare a character array to hold a string, it is crucial to allocate enough space not only for the characters in the string itself but also for the null terminator. The null terminator is a single character ('\0') that signals the end of the string to the C runtime. If you forget to reserve space for the null terminator, your string may not be properly recognized, leading to unpredictable results.

main.c


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#include <stdio.h>

int main() {
    // Declare a character array with enough space for "Hello" and the null terminator
    char greeting[6] = "Hello";

    // Print the string
    printf("%s\n", greeting);

    return 0;
}

In this code, you see a character array named greeting declared with a size of 6. This size is chosen because the string "Hello" has 5 characters, and you need one extra space for the null terminator ('\0'). Initializing the array with the string literal "Hello" automatically adds the null terminator at the end. If you had declared the array with only 5 elements, there would be no room for the null terminator, and the string would not be properly formed.

main.c


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#include <stdio.h>

int main() {
    // Incorrect: not enough space for the null terminator
    char word[4] = "Test";

    // Attempt to print the string
    printf("%s\n", word);

    return 0;
}

If you declare a character array that is too small for the intended string plus the null terminator, as in the previous example, you risk causing undefined behavior. The string may not be properly terminated, which can result in extra characters being printed, memory corruption, or crashes. Always ensure your character array is large enough to hold all desired characters plus the null terminator.

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Suggested prompts:

Can you explain what a null terminator is and why it's important?

What happens if I forget to include space for the null terminator in my array?

Can you give more examples of properly sized character arrays for different strings?

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Definition

main.c


              1234567891011
            
#include <stdio.h>

int main() {
    // Declare a character array with enough space for "Hello" and the null terminator
    char greeting[6] = "Hello";

    // Print the string
    printf("%s\n", greeting);

    return 0;
}

main.c


              123456789101112
            
#include <stdio.h>

int main() {
    // Incorrect: not enough space for the null terminator
    char word[4] = "Test";

    // Attempt to print the string
    printf("%s\n", word);

    return 0;
}

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Kiitos palautteestasi!

Osio 2. Luku 1