can't figure out a loop...

i finally crunched this program out... sorry for all the confusion, i'm new to C++ and am anxious to learn... the program below works fine but i need it to repeat a certain section if they enter a number that's not 4 digits long... i have it to say "Must be 4 digit number." but then it kicks out of the program, i know it's because of the "system(pause)" thing, but i have that in there only until i get the loop to work... i want it to keep asking them for a 4 digit num. until they enter a 4 dig. number.... thanks guys...

Code:

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>
#include <process.h>
#include <ctype.h>
#include <iostream.h>

char initial[5];     //declaration of variables and character string
int initialint, i, x, y, num;

void swap(int a, int b); // function prototypes for swapping/sorting.
void sort_des();
void sort_asc();

void main()
{

	cout<<"Please enter a 4 digit non-zero number..."<<" ";  //gets initial value
	cin>>initial;
	initialint=strlen(initial);
	if(initialint!=4)          //checks to see if number is 4 digits in length
	{
		cout<<"Must be a 4 digit number."<<endl;
        system("pause");
	}

	for(i=0; i<4; i++)
	{
		if(!isdigit(initial[i]))   //makes sure it is only digits and not letters or characters or something
		{
			cout<<"Must be numbers only."<<endl;
			system("pause");
		}
	}

	 while(strcmp(initial, "6174")!=0)  //checks to see if it is 6174 or not
	{
		cout<<""<<endl;
		sort_des();                //prints out the new numbers of the desc. and asc. strings
		x=atoi(initial);
		cout<<"  "<<initial<<endl;
		sort_asc();
		y=atoi(initial);
		cout<<"- "<<initial<<endl;

		if(x==y)      // this is to exempt the '9999, 8888, etc.' or zero
		{
			cout<<"Does not apply..."<<endl;
			break;
		}

		num=x-y;   // subtraction for descending and ascending
		sprintf(initial, "%4d", num);
		cout<<"------"<<endl;
		cout<<"  "<<initial<<endl;

        cout<<""<<endl;    // repeated this section of code to double up the "6174" at the end like on the homework paper.
		sort_des();
		x=atoi(initial);
		cout<<"  "<<initial<<endl;
		sort_asc();
		y=atoi(initial);
		cout<<"- "<<initial<<endl;

		if(x==y)
		{
			cout<<"Does not apply..."<<endl;
			break;
		}

		num=x-y;
		sprintf(initial, "%4d", num);
		cout<<"------"<<endl;
		cout<<"  "<<initial<<endl;
	}

	cout<<""<<endl;
	system("pause");
}



void swap(int a, int b)   // function definition for swapping characters in the string
{
char t;

	t=initial[a];
	initial[a]=initial[b];
	initial[b]=t;
}

void sort_des()         //function definition for sorting characters into descending order
{
int s, f;

	for(s=0; s<initialint-1; s++)
	{
		for(f=s+1; f<initialint; f++)
		{
			if(initial[f]>initial[s]) swap(f, s);
		}
	}
}

void sort_asc()        //function definition for sorting characters into ascending order
{
int s, f;

	for(s=0; s<initialint-1; s++)
	{
		for(f=s+1; f<initialint; f++)
		{
			if(initial[f]<initial[s]) swap(f, s);
		}
	}
}

i know the loop needs to be right around in here, but i'm not certain how to do it...

Code:

if(initialint!=4)          //checks to see if number is 4 digits in length
	{
		cout<<"Must be a 4 digit number."<<endl;
        system("pause");
	}

while(initialint!=4) should work instead of if(initialint!=4)

Code:

do             
{              
     cout<<"Please enter a 4 digit non-zero number..."<<" ";            
     cin>>initial;
}while(initial.size() != 4);

I think that will work

deepfrye: didn't work...

what didnt work about it?

This will work:

Code:

do             
{              
     cout<<"Please enter a 4 digit non-zero number..."<<" ";            
     cin>>initial;
}while(strlen(initial) != 4 || atoi(initial) == 0);

thanks, i appreciate it!

You don't see my reply, man?
All ready complete, man.
+Not limit number inputed.
+Check number or char
+Check size of number

I've completed everything for you, man.

Read carefully before post again, man.

Code:

//sort number
//mybe algorithm is Bubble Sort
//a bruce force algorithm
//optimized for check input buffer
#include <iostream>
using namespace std;
////////////////////////////////////////////////////////////
//convert from a character to a number
////////////////////////////////////////////////////////////
int chartoint(char c)
	{
		char buffer[2];
		buffer[1]=0;//string need to be terminated by ZERO
		buffer[0]=c;
		return atoi(buffer);
	}
////////////////////////////////////////////////////////////
//use to swap
////////////////////////////////////////////////////////////
void c_swap(char &a, char &b)
	{
		char buffer;
		buffer=a;
		a=b;
		b=buffer;
	}
////////////////////////////////////////////////////////////
//check "number" is number or not
////////////////////////////////////////////////////////////
bool checknumberstring(char*s)
	{
		int l = strlen(s);
		for (int i=0; i<l+1;i++)
				if (s[i]<'0' && s[i]>'9')
					return false;
		return true;
	}
////////////////////////////////////////////////////////////
#define	NUMBER	10
////////////////////////////////////////////////////////////
//main here//
////////////////////////////////////////////////////////////
int main()
	{
	char initialdigit [NUMBER];
	unsigned int firstinteger;
////////////////////////////////////////////////////////////
	cout<<"Please enter a non-zero digit number..."<<endl;
	fgets(initialdigit, NUMBER, stdin);
////////////////////////////////////////////////////////////
	if (strlen(initialdigit)!=NUMBER-1 || checknumberstring(initialdigit)==false) 
		{
			cout << "Error! Input..." << endl;
			system("PAUSE");
			return 1;
		}
////////////////////////////////////////////////////////////
	firstinteger = atoi (initialdigit);
////////////////////////////////////////////////////////////
	if (firstinteger > 0)
		{
		for (int i=0; i<NUMBER-1; i++)
			for (int j=0; j<NUMBER-1; j++)
				if (chartoint(initialdigit [j]) < chartoint(initialdigit [j+1]))
					c_swap(initialdigit [j], initialdigit [j+1]);
		}
////////////////////////////////////////////////////////////
	cout<<initialdigit<<endl;
	system("PAUSE");
////////////////////////////////////////////////////////////
	return 0;
	}
////////////////////////////////////////////////////////////