can't understand the increment used here...

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  1. #1
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    Question can't understand the increment used here...

    whats the reason behind usin' another (i = i + 1) in the 2nd 'for loop'?
    i'm very new at C,and i posted this at another forum but didn't quite get a good enough answer, so pls go easy on me! thanks!!


    Code:
    #include <stdio.h>
    
    main()
    {
    char first[21];
    char sur[21];
    char buffer[42];
    int i, j;
    
    printf("Please enter your first name: ");
    fflush(stdin);
    scanf("%[^\n]", first);
    printf("Please enter your last name: ");
    fflush(stdin);
    scanf("%[^\n]", sur);
    
    /*
    * First, copy the first name into the buffer, a la strcpy()
    
    */
    for (i = 0; first[i] != '\0'; i = i + 1)
    buffer[i] = first[i];
    
    /*
    * Add the space
    */
    buffer[i] = ' ';
    i = i + 1; /* don't forget to adjust the counter */
    
    /*
    * Next, concatentate the surname onto the buffer, a la strcat()
    * Notice that the for loop has TWO increments
    */
    for (j = 0; sur[j] != '\0'; j = j + 1, i = i + 1)
    buffer[i] = sur[j];
    buffer[i] = '\0'; /* don't forget to terminate the string */
    
    printf("The full name is >>%s<<\n", buffer);
    
    fflush(stdin);
    getchar();
    }

  2. #2
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    j is used as the index into the 'sur' array while i is used as the index into the 'buffer' array.
    When 'first' was copied to 'buffer the same index value could be used because first[0] was copied to buffer[0], first[1] to buffer[1] and so on. But when coppying from the 'sur' array the program is adding to the buffer array from the current possition not starting from the start.

  3. #3
    and the hat of wrongness Salem's Avatar
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    > whats the reason behind usin' another (i = i + 1) in the 2nd 'for loop'?
    Well you can try it without, and observe the difference.

    Also, read the FAQ and figure out why fflush(stdin) is bad.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
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  4. #4
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    Every iteration, i is incremented as well as j. Simple as that.

  5. #5
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    Thumbs up

    thanks all you guys!!!

    Quantum1024 -i like your answer the most, thats what i couldn't understand before!! thanks a ton!!

    Salem - i tried without it and it didn't print anythin' after the space-char. but i couldn't understand it before...i do now!thanks for the heads-up for fflush(stdin), i'll check it out!

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