Thread: 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

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

>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;
}

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

>>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.