Assign strings in C

Let's analyze these two C codes and see why they behave so much.

Code Example 1:

 <code class="language-c">#include <stdio.h> int main(void) { char *string = "wello, world!"; string[0] = 'h'; puts(string); }</stdio.h></code>

This code declares a character pointer string and initializes it to point to a string literal "wello, world!" . String literals are usually stored in read-only data segments of the program. Trying to modify string[0] will attempt to modify read-only memory, resulting in a segmentation fault.

Code Example 2:

 <code class="language-c">#include <stdio.h> int main(void) { char string[] = "Wello, world!"; string[0] = 'H'; puts(string); }</stdio.h></code>

This code declares a character array string and initializes it with the string literal "Wello, world!" . Here, the contents of the string literal are copied into string array. string array is now located in the program's stack memory, and its contents are modifiable. Therefore, string[0] = 'H'; can successfully modify the first character to 'H', puts(string) will correctly print "Hello, world!".

Key Differences: Pointers vs. Arrays

The key is that the first piece of code uses pointers, while the second piece of code uses arrays.

• Pointer: char *string declares a character pointer that stores the address of the string in memory. The pointer itself is modifiable, but the properties of the memory area it points to (for example, read-only) are not alterable.

• Array: char string[] declares an array of characters that allocate a continuous piece of space in memory to store strings. The array name string in most cases (except for operands as sizeof operators or operands as & operators) will decay to a pointer to the first element of the array, but the array itself is not a pointer. The contents of the array can be modified.

Summarize:

These two examples highlight the important difference between pointers and arrays in C. Understanding this distinction is essential to avoid memory-related errors. Modifying the string literal directly results in undefined behavior, while using arrays can safely modify the string content. Be sure to pay attention to whether you are operating pointers or arrays and perform corresponding operations according to their characteristics.

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