#define  CUSTOMERS   10                                     
                                                               
   main( )                                                     
   {                                                           
       char  first_name[20][10], second_name[20][10],          
             surname[20][10], name[20][20],                    
             telephone[20][10], dummy[20];                     
                                                               
       int   i,j;                                              
                                                               
       printf("Input names and telephone numbers \n");         
       printf("?");                                            
       for(i=0; i < CUSTOMERS ; i++)
       {                                    
            scanf("%s %s %s %s", first_name[i],                 
                  second_name[i], surname[i], telephone[i]);   
                                                               
           /* converting full name to surname with initials */
 
                                                               
           strcpy(name[i], surname[i] );                       
           strcat(name[i], ",");                               
           dummy[0] = first_name[i][0];                        
           dummy[1] = '\0';                                    
           strcat(name[i], dummy);                             
           strcat(name[i], ".");                               
           dummy[0] = second_name[i][0];                       
           dummy[1] = '\0';                                    
           strcat(name[i], dummy);                             
       }                                                       
       /* Alphabetical ordering of surnames */
for(i=1; i <= CUSTOMERS-1; i++)                     
              for(j=1; j <= CUSTOMERS-i; j++)                  
                 if(strcmp (name[j-1], name[j]) > 0)           
                 {                                             
                 /* Swaping names */
                           
                     strcpy(dummy, name[j-1]);                  
                     strcpy(name[j-1], name[j]);                
                     strcpy(name[j], dummy);                    
                                                               
                 /* Swaping telephone numbers */
               
                    strcpy(dummy, telephone[j-1]);             
                    strcpy(telephone[j-1],telephone[j]);       
                    strcpy(telephone[j], dummy);               
                 }                                             
          /* printing alphabetical list */
                        
       printf("\nCUSTOMERS LIST IN ALPHABETICAL ORDER \n\n");  
       for(i=0; i < CUSTOMERS ; i++)                           
          printf("   %-20s\t %-10s\n", name[i], telephone[i]); 
   } 






Output                                                      
                                                               
   Input names and telephone numbers                           
   ?Gottfried Wilhelm Leibniz 711518                           
   Joseph Louis Lagrange 869245                                
   Jean Robert Argand 900823                                   
   Carl Freidrich Gauss 806788                                 
   Simon Denis Poisson 853240                                  
   Friedrich Wilhelm Bessel 719731                             
   Charles Francois Sturm 222031                               
   George Gabriel Stokes 545454                                
   Mohandas Karamchand Gandhi 362718                           
   Josian Willard Gibbs 123145                                 
  
 CUSTOMERS LIST IN ALPHABETICAL ORDER                        
                                                               
      Argand,J.R            900823                             
      Bessel,F.W          719731                             
      Gandhi,M.K             362718                             
      Gauss,C.F             806788                             
      Gibbs,J.W              123145                             
      Lagrange,J.L        869245                             
      Leibniz,G.W          711518                             
      Poisson,S.D           853240                             
      Stokes,G.G             545454                             
      Sturm,C.F              222031