simple string question

This is a discussion on simple string question within the C Programming forums, part of the General Programming Boards category; i have written the following prog. for reversing a string,output is showing nothing after the 'the reversed stringis' plz have ...

  1. #1
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    simple string question

    i have written the following prog. for reversing a string,output is showing nothing after the 'the reversed stringis'
    plz have a look and rectify my errors
    #include<stdio.h>
    # include<string.h>

    void main()
    {
    char source[20];
    char*str;
    char str1[20];
    int i,j=0;
    clrscr();
    printf("enter your city");
    scanf("%s",source);
    i=strlen(source);
    printf("%d",i);
    str=source[i-1];


    while(j<=i)
    {

    str1[j]=*str;

    j++;str--;
    }
    str1[j]='\0';
    printf("the reversed string %s",str1);

    getch();
    }


    and wud somebody plz explain me the concept of dummy operartors

  2. #2
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    Not sure if this is the only error because I don't use scanf() and printf() much because I mainly do embedded stuff, but the line before the while should be

    &source[i-1].

    str is a pointer so you need to put the character's address in there, not the character.
    Make sure that scanf gives you a null terminated string as well otherwise strlen will not work.

    Davey

  3. #3
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    >output is showing nothing after the 'the reversed stringis'
    Without looking closely at your code, I would guess that you are copying the null character into index 0 of the array. This makes it an empty string which will print nothing.

    I would recommend comparing your code to the following. Try to determine why I chose to do certain operations differently. Using the information on these forums and the FAQ provided on this web site, you can do so easily.
    Code:
    #include <stdio.h>
    #include <string.h>
    
    int main()
    {
      char str[BUFSIZ];
    
      printf("Enter a string: ");
      fflush(stdout);
      if (fgets(str, sizeof str, stdin) != NULL) {
        size_t s, e;
        char *newline = strchr(str, '\n');
    
        if (newline != NULL) {
          *newline = '\0';
        }
        for (s = 0, e = strlen(str) - 1; s < e; s++, e--) {
          char save = str[s];
          str[s] = str[e];
          str[e] = save;
        }
        printf("The reversed string is: \"%s\"\n", str);
      }
    
      return 0;
    }

  4. #4
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    thanx davey,
    that worked, i missed the &source[i-1],
    so whats the purpose of dummy variables in the progs.

  5. #5
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    >>so whats the purpose of dummy variables in the progs.
    Your question is too vague. Please describe the context in which these dummy variables are used.

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