C String: Declare, Modify and Length (Simple Note)

Simple Note

Code

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

int main () {
    /**
     * declare, modify and length
     *
     */
    // declare string
    char* chPtr = "abcdefg";// will add '\0' at the tail automatically
    char chArr[] = "bbcdefg";
    char chArrTwo[] = {'c', 'b', 'c', 'd', 'e', 'f', 'g'}; // will not add '\0' automatically
    char chArrThree[] = {'d', 'b', 'c', 'd', 'e', 'f', 'g', '\0', '\0', '\0'};

    // output string
    printf("chPtr = %s\n", chPtr);
    printf("chArr = %s\n", chArr);
    printf("chArrTwo = %s\n", chArrTwo);
    printf("chArrThree = %s\n", chArrThree);

    // output length by sizeof
    // 4, the size of pointer
    printf ("\nLenbgh of char pointer = %d\n", sizeof(chPtr));
    // 8, the size of whole array
    // including a, b, c, d, e, f, g and '\0' (the terminate char added automatically)
    printf ("Length of char array = %d\n", sizeof(chArr));
    // 7, no terminate char
    printf ("Length of char array two = %d\n", sizeof(chArrTwo));
    // 10, including 3 terminate char
    printf ("Length of char array three = %d\n", sizeof(chArrThree));

    // output length by strlen
    // 7, only count the length before first '\0' or array length
    printf ("\nLenbgh of char pointer = %d\n", strlen(chPtr));
    printf ("Length of char array = %d\n", strlen(chArr));
    printf ("Length of char array two = %d\n", strlen(chArrTwo));
    printf ("Length of char array three = %d\n", strlen(chArrThree));

    // replace first char
    // cannot modify char points by a char pointer
    // this line below cause the runtime error
    // chPtr[0] = 'w';
    chArr[0] = 'x';
    chArrTwo[0] = 'y';
    chArrThree[0] = 'z';

    // output string again
    printf("\nchPtr = %s\n", chPtr);
    printf("chArr = %s\n", chArr);
    printf("chArrTwo = %s\n", chArrTwo);
    printf("chArrThree = %s\n\n", chArrThree);
    
    system("PAUSE");
}

Result

Reference

cplusplus
http://www.cplusplus.com/reference/cstring/strlen/

Thread at SF: Is it possible to modify a string of char in C?
http://stackoverflow.com/questions/1011455/is-it-possible-to-modify-a-string-of-char-in-c

Download

Code at github
https://github.com/benbai123/C_Cplusplus_Practice/blob/master/C_StringProcessing/string_declare_modify_and_length.c