I'm a beginner in learning C programming language. I've been having some problems with my problem, i.e., pin masking with 3 attempts for my ATM banking system. Furthermore, I've used goto statement, however, we are restricted to use this statement. So how can I remove the goto statement and use loop instead? Badly need help. Thank you! Code is down below.

#include <stdio.h>
#include <conio.h>
#include <stdlib.h>
#include <string.h>
#include <windows.h>

#define ENTER 13
#define TAB 9
#define BCKSPC 8


int pinValidation()
{
    char pwd[20], pin[]="5263";
    int attemptCount=1;
    char ch;
    start:
    int i=0;

        //attempts count
    do{
        printf("Enter your pin: ");
        while(1)
            {
                ch=getch();
                if(ch == ENTER || ch == TAB)
                {
                    pwd[i]='\0';
                    break;
                }
                else if(ch == BCKSPC)
                {
                    if(i>0)
                    {
                        i--;
                        printf("\b \b"); //for the cursor
                    }
                }
                else if(pwd[i]=ch)
                {
                    pwd[i]=ch;
                    i  ;
                    printf("*");
                }
            }
    }while(ch != ENTER);

        if(strcmp(pin,pwd)==0 && attemptCount <= 4)
            {
                Beep(1000,500);
                Beep(1000,600);
                printf("\nAccess granted");
                
            }
        
        else
        {
            Beep(750, 800);
             printf("\n\nUnsuccessful login %d of 3 attempt\n\n", attemptCount);
             attemptCount  ;
            if (attemptCount < 4) goto start;
            if (attemptCount == 4) {
                goto reached;
            }
            getch();
            reached:
            Beep(800,800);
            Beep(800,800);
            Beep(800,900);
            printf("Attempt reached");
             
        }
        getch();
            
}
        

int main()
{
    pinValidation();
    return 0;
}

/*

    start
    initialize variables
    input pin
    if pin is != inputed pin && attempt < 3
        print unsuccessful login %d attempt left
    else if pin != inputed pin && attempt  = 3
        print "attempt reached"
    else if pin == inputted pin && attempt <= 3
        print "Access granted"

*/

CodePudding user response：

This looks like a bit of course work?! ;-)

Nonetheless, hope this helps you understand the approach...

#include <stdio.h>
#include <stdbool.h>
#include <conio.h>
#include <stdlib.h>
#include <string.h>
#include <windows.h>

#define ENTER 13
#define TAB 9
#define BCKSPC 8

#define MAXATTEMPTS 4
#define MAXPINLENGTH 4

void getPin(char* pinCapture, size_t size)
{
    char ch;
    int pinLength = 0;
    pinCapture[pinLength] = '\0';

    printf("Enter PIN? ");
    do
    {
        ch = getch();
        switch (ch)
        {
            // Characters to ignore...
            case ENTER:
            case TAB:
                break;
            // Allow user to delete previous digits
            case BCKSPC:
                if (pinLength > 0)
                {
                    pinLength--;
                    printf("\b \b");
                }
                break;
            // Add character to PIN...
            default:
                pinCapture[pinLength] = ch;
                pinLength  ;
                printf("*");
                break;
        }
    } while (ch != ENTER && pinLength < size);
    pinCapture[pinLength] = '\0';
    printf("\n");
}

bool pinValidation()
{
    char validPin[] = "1234";
    int attemptCount = 0;
    char pin[5];

    while (attemptCount < MAXATTEMPTS && strcmp(pin, validPin) != 0)
    {
        attemptCount  ;
        getPin(pin, MAXPINLENGTH  1);
        if (strcmp(pin, validPin) != 0)
        {
            printf("Invalid attempt. You have %d more trys.\n", MAXATTEMPTS - attemptCount);
        }
    }
    if (strcmp(pin, validPin) == 0)
    {
        return true;
    }
    else
    {
        return false;
    }
}

int main()
{
    if (pinValidation())
    {
        printf("Access granted.\n");
    }
    else
    {
        printf("Access denied.\n");
    }
    return 0;
}

/*
    start
    initialize variables
    input pin
    if pin is != inputed pin && attempt < 3
        print unsuccessful login %d attempt left
    else if pin != inputed pin && attempt  = 3
        print "attempt reached"
    else if pin == inputted pin && attempt <= 3
        print "Access granted"
*/