[linux-help] Re: C help!!(OT)

[John Reinke <jmreinke@xxxxxxxxxxxxxxxxxxx>]

I looked at your code briefly. It looks like you fail to allocate memory
to store the strings in, and don't forget that gets() is dangerous.
Whether that is related to your problem, you'll have to figure out, but
that's all I'll offer.

Your instructor should be a good source of assistance. When it comes to
asking questions like this on mailing lists, don't expect many answers,
since the fine line between helping others and doing homework for others
is difficult to discern.

Good luck,
John

On Tue, 24 Apr 2001, Weqaar Ali Janjua wrote:

> 
> Hello guyz,
> 
>      This question is kinda out of the list discussion but any help will be 
> greatly appreciated. Can anybody help me out with the following C 
> programming problem:
> 
> I make a structure with some char type variables:
> -------------------START OF CODE------------------------------
> /*POINTER TEST*/
> #include <stdio.h>
> 
> //Structure Definition
> struct weqaar {
> char *fish;
> char *sick;
> };
> 
> int main(void) {
> struct weqaar a; //initializing variable of type 'struct weqaar'
> struct weqaar b; //initializing variable of type 'struct weqaar'
> struct weqaar *ptr;
> ptr=&a;
> 
> printf("\nenter value of a.fish:");
> gets(a.fish);
> printf("\nenter value of a.sick:");
> gets(a.sick);
> printf("%s\t%s",a.fish,a.sick);
> printf("\n");
> //checking the values stored in mem.
> printf("b.fish is %s,\tb.sick is %s",b.fish,b.sick);
> //
> printf("\n");
> printf("\nenter value of b.fish:");
> gets(b.fish);
> printf("\nenter value of b.sick:");
> gets(b.sick);
> printf("%s\t%s",b.fish,b.sick);
> printf("\n");
> printf("%s\t%s",a.fish,a.sick);
> printf("\n");
> printf("PTR values are: %s\t%s\n",ptr->fish,ptr->sick);
> printf("Mem. location addresses of b.fish and b.sick are %p 
> %p",b.fish,b.sick);
> return 0;
> }
> -------------------END OF CODE------------------------------
> Now I execute the program and store some data in the variables suppose:
> I enter 'ash' in 'a.fish' and 'dish' in 'a.sick' AND 'madonna' in 'b.fish' 
> and 'nicole' in 'b.sick' and then terminate the program.
> When I run the program again  the commented line in my C prog. gives me the 
> output "madonna    nicole", that means the values are still 
> there(structures being of storage type static) and my last line prints out 
> the memory addresses '0C5B' and 'FFF0' of variables 'b.fish' and 'b.sick' 
> and the program terminates exit(1). Then I note these addresses and write 
> another piece of code:
> -------------------START OF CODE------------------------------
> #include <stdio.h>
> 
> int main(void) {
> char *hackPtr=0xFFF0; //note that line
> printf("%s",hackPtr);
> return 0;
> }
> -------------------END OF CODE------------------------------
> now note the line 'char *hackPtr=0xFFF0;' , I have to specify 0x before the 
> address I got from the output of my first program, If I dont specify '0x' 
> the compiler takes it as a string value, my core question is how can I get 
> the accurate/in-the-form memory address as '0xFFF0'?? and how can I make my 
> other program modify the value in that location???can I read the string in 
> that location with my second program???or do I have to decode the value I 
> get(maybe HEX)???? AND how can I make structure of any non-static storage 
> type?????
> Thanx in advance,
> Weqaar Ali Janjua
> BECE
> Wichita State University
> 
> 
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