A problem with a pointer to a string

[edd1986]

Hi. i was bored so i wrote a very simple encryption program using a global variable 'text' (the text to be encrypted) which i pass into two functions, encrypt and decrypt. This works fine, but as i've been told before that global variables are bad (i'm unsure why) i want to use a pointer to text instead of the global variable. However i don't have a very good understanding of pointers at all, so both my attempts to implement the code below with pointers failed miserably. Any help regarding this would be greatly appreciated.

Thanks

My code:

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

void encrypt(char[]);
void decrypt(char[]);

char text[100];
    
int main(void)
{     
   char decision[10];
    
   printf("Enter text to be encrypted:");
   fgets(text, sizeof(text), stdin);
   text[strlen(text)-1] = '\0';
    
   encrypt(text);
   printf("%s\n", text);
	
   printf("Do you want to decrypt the string?(yes/no)\n");
   fgets(decision, sizeof(decision), stdin);
   decision[strlen(decision)-1] = '\0';
	
   if (strcmp(decision, "yes") == 0)
   {
      decrypt(text);
      printf("%s\n", text);
   }
   return 0;
}

void encrypt(char txt[])
{
    int i;
    
    for (i = 0; i < strlen(txt); i++)
    {
        txt[i]++;
    }
}

void decrypt(char txt[])
{
    int i;
    
    for (i = 0; i < strlen(txt); i++)
    {
        txt[i]--;
    }
}

[Dave_Sinkula]

My test:

Enter text to be encrypted:hello world
ifmmp!xpsme
Do you want to decrypt the string?(yes/no)
yes
hello world

What's the question? If you just want text local to main, do so.

[edd1986]

my understanding was that if the text variable was not global, but local, i would be able to pass it into my functions, but i would not be able to change the variable from the function itself, unless i used a pointer to the variable. sorry if it was unclear but my question was simply how would i go about implementing the code i had already written (above), with a pointer to the variable 'text' (where text would be inside main()) instead of using 'text' as a global variable. Hope this makes sence.

Thanks

[Dave_Sinkula]

I may me a little off at the moment, but this does exactly the same as when text is global.

int main(void)
{     
   char text[100];
   char decision[10];
    
   printf("Enter text to be encrypted:");
   fgets(text, sizeof(text), stdin);
   text[strlen(text)-1] = '\0';
    
   encrypt(text);
   printf("%s\n", text);
	
   printf("Do you want to decrypt the string?(yes/no)\n");
   fgets(decision, sizeof(decision), stdin);
   decision[strlen(decision)-1] = '\0';
	
   if (strcmp(decision, "yes") == 0)
   {
      decrypt(text);
      printf("%s\n", text);
   }
   return 0;
}

unless i used a pointer to the variable

These are passing pointers.

void encrypt(char[]);
void decrypt(char[]);

[edd1986]

Thanks i did not realise this.