EXAMPLE CLASSIQUE: CONVERTION ENTIER EN CHIFFRE ROMAINE ET <<-- (LANG- C )

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

void roman()

    {
    	
    	int ones, tens, hundreds, thousands, temp, input, x;
    	char rO[100] = "";
    	char rTens[100] = "";
    	char rHundreds[100] = "";
    	char rThousands[100] = "";
    	char *rTemp;
    	
    	
    	for(;;)


        	{
                        printf( "Votre nombre: (si 0 - revenir dans menu)  ");
        		scanf("%d",& input);
                                        if(input==0)  break;
        		printf( "\n\nArabic %d: ",input);
        		       		thousands = input/1000;
        		hundreds = (input-(thousands*1000))/100;
        		tens= (input-(thousands*1000 + hundreds*100))/10;
        		ones= (input-(thousands*1000 + hundreds*100 + tens*10));
        		temp = 0;
        		
        	while(temp!=thousands)


            	{
            		rTemp = "M";
            		strcat(rThousands, rTemp);
            		temp++;
            	}
            	
            	temp = 0;
            	
            	if(temp!=hundreds)


                	{
                		if(hundreds==1) strcpy(rHundreds, "C");
                		if(hundreds==2) strcpy(rHundreds, "CC");
                		if(hundreds==3) strcpy(rHundreds, "CCC");
                	if(hundreds==4) strcpy(rHundreds, "CD");
                		if(hundreds==5) strcpy(rHundreds, "D");
                		if(hundreds==6) strcpy(rHundreds, "DC");
                		if(hundreds==7) strcpy(rHundreds, "DCC");
                		if(hundreds==8) strcpy(rHundreds, "DCCC");
                		if(hundreds==9) strcpy(rHundreds, "CM");
                	}
                	
              
                	temp = 0;
                	
              
                	if(temp!=tens)


                    	{
                    		if(tens==1) strcpy(rTens, "X");
                    		if(tens==2) strcpy(rTens, "XX");
                    		if(tens==3) strcpy(rTens, "XXX");
                    		if(tens==4) strcpy(rTens, "XL");
                    		if(tens==5) strcpy(rTens, "L");
                    		if(tens==6) strcpy(rTens, "LX");
                    		if(tens==7) strcpy(rTens, "LXX");
                    		if(tens==8) strcpy(rTens, "LXXX");
                    		if(tens==9) strcpy(rTens, "XC");
                    	}
                    	
              
                    	temp = 0;
                    	
                    	
                    	if(temp!=ones)


                        	{
                        		if(ones==1) strcpy(rO, "I");
                        		if(ones==2) strcpy(rO, "II");
	                        	if(ones==3) strcpy(rO, "III");
                        		if(ones==4) strcpy(rO, "IV");
                        		if(ones==5) strcpy(rO, "V");
                        		if(ones==6) strcpy(rO, "VI");
                        		if(ones==7) strcpy(rO, "VII");
                        		if(ones==8) strcpy(rO, "VIII");
                        		if(ones==9) strcpy(rO, "IX");
                        	}
                        	
                        	
                        	printf( "\nRomain : %s%s%s%s", rThousands, rHundreds , rTens , rO);
                        		printf( "\n\n");
                        	
                        	strcpy(rO, "");
                        	strcpy(rTens, "");
                        	strcpy(rHundreds, "");
                        	strcpy(rThousands, "");
                    }
                    	
   
                         main();         
                        
                }

void arabic()
    {
    char a[15]; 
    int p,i,rom,flag,x,rep;
do{    
printf("Entrez  Romain Nombre :"); 	
    scanf("%s",a);
    for(x=0,p=0,flag=0,rom=0,i=strlen(a)-1; i>=0; i--)        {
        	if (a[i]=='i' || a[i]=='I') x=1; 
                  if (a[i]=='v' || a[i]=='V') x=5; 
        	if (a[i]=='x' || a[i]=='X') x=10; 
        	if (a[i]=='l' || a[i]=='L') x=50; 
        	if (a[i]=='c' || a[i]=='C') x=100; 
        	if (a[i]=='d' || a[i]=='D') x=500;
        	if (a[i]=='m' || a[i]=='M') x=1000; 
        	
        	if (x<p) flag = -1; 
        	else flag = 1;
        
                rom= rom+(x*flag);
                p=x;    
        	}
        printf("valeur numerique -->>> : %d",rom);
     printf("\nEncore -1; autre touche - revinir  dans menu\n"); scanf("%d",&rep);  
    }while(rep==1);
 main();
}


main()
{
char lettre;
printf("\n *****************************\n");
    	printf(" * A R A B I Q U E - R O M A I N *\n");
    	printf( "      *C O N V E R T I O N*\n");
                  printf(" *****************************\n");


printf("Conversion ARABIC-->>>ROMAIN: appuez A\n");
printf("Conversion ROMAIN-->>>ARABIC: appuez R\n");
printf("Sortir: appuez Q\n"); scanf("%c",&lettre); lettre=toupper(lettre);
if(lettre!='A'&&lettre!='R'&&lettre!='Q')
do{
 printf("\nVotre choix dans menu,s.v.p.: A,R,Q:   \n");scanf("%c",&lettre); lettre=toupper(lettre);
}while(lettre!='A'&&lettre!='R'&&lettre!='Q');
if (lettre=='A') arabic();
if (lettre=='R') roman();
else printf("\nMerci et au revoir!");

}