Thread: masked with asterisk(*)?

Code:

char buf[50];
fgets(buf, sizeof(buf), stdin);

..what does sizeof(buf), stdin do? What does it mean?

..and this one? I don't get this one also...

Code:

/* ... include headers ... */

. . .
void readCredentials(char *name, size_t name_maxlen, char *passcode, size_t passcode_maxlen);
void analyzeCredentials(const char *name, const char *passcode);
char readOption();

. . .
int main()
{

Code:

readCredentials(name, sizeof(name) - 1, passcode, sizeof(passcode) - 1);

...and that... what does it mean if we put -1 there?

Code:

    loop:
    {
        char name[20] = "";
        char passcode[20] = "";
        readCredentials(name, sizeof(name) - 1, passcode, sizeof(passcode) - 1);
        analyzeCredentials(name, passcode);
    }
    if (readOption() == 'R')
        goto loop;

..is that the way how a while...do loop works?

what's the difference between do...while and while...do? I know that they're not the same, am I right?

How to mask the password with "*" has been asked many times and there's no standard way. If you do a search, I'm sure you will find lots of info.

I found this one from:
http://www.gohacking.com/2007/12/c-p...d-mask-it.html

I made some modification... -_+

Code:

#include<stdio.h>
#include<conio.h>

char pw[25], ch;
int i;

int main()
{
    clrscr();
    puts("Enter password");

    while(1)
    {
        if(i<0)
        i=0;
        ch=getch();
        if(ch==13)
        break; /*13 is ASCII value of ENTER*/

        if(ch==8) /*ASCII value of BACKSPACE*/
       {

            putch('\b');
            putch(NULL);
            putch('\b');
            --i;
            continue;
        }

        pw[i++]=ch;
        ch='*';
        putch(ch);
    }

    pw[i]='\0';
    printf("\n\n%s",pw);
    getch();

    return 0;
}

...can someone please explain this to me? Coz, I don't still get it...


...hmmm, anyways, thank you very much to all of you who have helped me... I really appreciate it... ^.^

>> ...can someone please explain this to me? Coz, I don't still get it...
Perhaps you can be a little more descriptive? Start by explaining what you do understand. It's important that you try, because it's part of asking a smart question. And experience explaining an algorithm is a fundamental part of any programmer's skill set.

Actually, your for example lacks correctness. For loops should be more like while since the increment comes after the body, before the next test.

Code:

i = 0;
loop: if ( i == 10 ) goto out;
/** body **/
i++;
goto loop;
out:

But that doesn't really help does it?

If I may give a further example of why to not use "goto", it is this: Your program fits fairly neatly on one page. In the real world of programming, you aren't going to have programs that fit neatly into one page. As an old Fortran programmer who has seen code of 10,00 lines and more with "gotos', it's no fun to try and figure out where you are and what is going on when you try to debug a program. Trust me, if you don't use cuss words now, and if you continue to use "gotos", you will eventually learn and say those words. Because 6 months from whenever you finish your program, when you go back and look at your program that is longer than a few pages, YOU will have a hard time debugging your OWN work.

...ok, so here I is something for you who have helped me... tada! no more goto's,, -_+ hehehehe....

Code:

#include<stdio.h>
#include<conio.h>

int main()
{
	char name[20], passcode[20], option;
	int x=0;

	do
	{
		clrscr();

		printf("\n\n\tEnter your name: ");
		gets(name);

		printf("\n\tEnter the passcode: ");
		gets(passcode);

		printf("\n\n\n\tPress \"Enter\" to proceed...");

		clrscr();

		printf("\n\n\n\tPlease wait. Analyzing data...");

		while(x < 5)
		{
			gotoxy(42,4); printf("|");
			sleep(1);
			x++;
			gotoxy(42,4); printf("/");
			sleep(1);
			x++;
			gotoxy(42,4); printf("-");
			sleep(1);
			x++;
			gotoxy(42,4); printf("\\");
			sleep(1);
			x++;
			gotoxy(42,4); printf("|");
			sleep(1);
			x++;
		}

		clrscr();

		printf("\n\n\n\tYour name is: ");
		textcolor(LIGHTBLUE); cprintf("%s", name);
		printf("\n\n\t");
		textcolor(LIGHTGRAY); cprintf("Verifying passcode");

		x=0;
		while(x < 7)
		{
			printf(".");
			sleep(1);
			x++;
			printf(".");
			sleep(1);
			x++;
			printf(".");
			sleep(1);
			x++;
			printf(".");
			sleep(1);
			x++;
			printf(".");
			sleep(1);
			x++;
			printf(".");
			sleep(1);
			x++;
			printf(".");
			sleep(1);
			x++;
		}

		do
		{
			clrscr();

			printf("\n\n\n\tThe passcode that you have entered is: ");

			if(!strcmp(passcode, "XMod749"))
			{
				textcolor(LIGHTBLUE+128); cprintf("ACCEPTED.");
				getch();
				return 0;
			}
			else
			{
				textcolor(LIGHTRED+128); cprintf("INVALID!");
				getch();
				printf("\n\n\t");
				textcolor(LIGHTGRAY); cprintf("What do you want to do?");
				printf("\n\n\t\tExit [E] or Retry [R]? ");
				option = getche();
				option = toupper(option);

				if(option=='E') return 0;

			}

		} while(option=='B'); /*duh!*/

	} while(option=='R');


	return 0;
}

..I have already tested it, and it's working! yeah! xD
...but do you see that line over there?

Code:

}while(option=='B'); /*duh!*/

....that's not actually what I want, I don't want the program to repeat the loop if the user enters B... what I actually want to put here is something that can repeat the loop if the user enters any characters other than E or R... You know what I'm saying? ...some sort of an error handler? (amiryt? error handler??) ...just like in the switch() statement... the default: thing.. yeah, that's what I mean... but, what should I put there? I have no idea what to put there, so I just put there while(option=='B');... If you can still remember the first source-code I've posted here (I think it's on the first page of this thread), the program was supposed to jump to pcode: when I was using the goto (btw, is goto a function?) ...how can I do the same using a do-while loop? ^.^

...uhmmm, one more thing, is there any such function as putch()? Will this help me make the program to "put" asterisk "characters" as the user types in the passcode?

....And btw, I'll share ya'll something about this asterisk thing... hehehe, lol.. xD
While I was trying to figure out how the heck am I going to make the program ouput asterisks as the user types in the passcode, something came into my mind... the toupper() and tolower() functions... I was wondering, if toupper() changes the character entered by the user into an upper-case character, and tolower() changes the character into a lower-case character... I tried this: toasterisks()! hahaha, lol.. xD ...and what did get?? Tada! ~CoMpiLer ErroR.

Code:

		while(x < 7)
		{
			printf(".");
			sleep(1);
			x++;
			printf(".");
			sleep(1);
			x++;
			printf(".");
			sleep(1);
			x++;
			printf(".");
			sleep(1);
			x++;
			printf(".");
			sleep(1);
			x++;
			printf(".");
			sleep(1);
			x++;
			printf(".");
			sleep(1);
			x++;
		}

can either be written without the while, or written differently using a loop:
Code:

Code:

		while(x < 7)
		{
			printf(".");
			sleep(1);
			x++;
                }

This one:

Code:

		while(x < 5)
		{
			gotoxy(42,4); printf("|");
			sleep(1);
			x++;
			gotoxy(42,4); printf("/");
			sleep(1);
			x++;
			gotoxy(42,4); printf("-");
			sleep(1);
			x++;
			gotoxy(42,4); printf("\\");
			sleep(1);
			x++;
			gotoxy(42,4); printf("|");
			sleep(1);
			x++;
		}

can also be written as a loop:

Code:

// At the beginning of the source.
     char spinstr[] = "|/-\\|";

//
             
		while(x < 5)
		{
			gotoxy(42,4); printf("%c", spins[x]);
			sleep(1);
			x++;
		}

(or you could remove the while, as it does exactly the same thing either way).

...thanks man,, that is really useful man.... ^.^

You should still replace gets.

ah, yes,, the gets()... lol, I forgot to change that...

There's no need for putch, a simple printf statement will do.

thankyou.. but how?

You can replicate any goto behavior with a loop - including this "default" behavior. A loop loops so long as the condition is true. So you need to think really hard what that condition should be. That's all, really.

awww, c'mon... I wouldn't post this if I have had already think of this really hard in the first place.. I just can't figure it out.. plus, my knowledge regarding C programming is limited, so I don't even have a clue... -_+

Originally Posted by ShadeS_07

ah, yes,, the gets()... lol, I forgot to change that...



thankyou.. but how?

Code:

printf("*");

would print an asterisk.

awww, c'mon... I wouldn't post this if I have had already think of this really hard in the first place.. I just can't figure it out.. plus, my knowledge regarding C programming is limited, so I don't even have a clue... -_+

You want not E or R, right? So that's what you do

Code:

while(not(option=='E' or option=='R'))

(provided you include <iso646.h>. If you don't want to include that, you have translate not and or into C:

Code:

while(!(option=='E'||option=='R'))

using the logical operators.)