switch case works like this:
Code:
switch ( variable that can be used as an integer )
{
  case #1: blah; blah; blah;break;
  case #2: blah; blah; blah;break;
  ...
  default: blah; blah; blah;break;
}
in your case:
Code:
    do{
        choice = mainMenu();   
        Stemplate();        
        switch ( choice )
        {
          case 1:
            do{
                loop = addItems(inventory,&arrayL);
              }while (loop);
            break;
          case 2:
            do{
                loop = deleteItems(inventory,&arrayL);
              }while (loop);
            break;

          case 3:  viewItems(inventory,arrayL); break;
          case 4:  sortItems(inventory,arrayL); break;
          case 5:  searchItems(inventory,arrayL);
          case 0:  exitScreen(); break;
          default:  puts("Invalid input");
        }
 
    saveData(inventory,arrayL);
    }while(choice != 0);