if(argc_cmd>0&&argc_cmd<4)//checking on the command line argument.
{
charch;//
printf("%s","Enter command >>");
while(scanf("%s",firstarg)!=1||(scanf("%d",&lesson_choice))!=1||lesson_choice<1||lesson_choice>15||strncmp(firstarg,"select",6)!=0)//Ensuring that "select"
{//is entered accurately and the selected value is within the correct range.