The expression after case can be plastic, character or live enumeration, but your a, b, c and d are undefined.
int main(void)
{
int I;
Carbonization grade;
Double integral;
for(I = 1; I < = 6; i++)
{
printf("[A]Select 1 \ n ");
printf("[B]Select 2 \ n ");
printf("[C]Select 3 \ n ");
printf("[D]Select 4 \ n ");
printf("[E]Select 5 \ n ");
printf("[0]exit \ n ");
Printf ("input grade:");
Scanf("%c ",& grade);
if(Grade ==“”)
Break;
Switch (grade)
{
Case "a": printf ("90 to100 \ n"); Break;
Case "b": printf ("80 to 90 \ n"); Break;
Case "c": printf ("70 to 80 \ n"); Break;
Case "d": printf ("60 to 70 \ n"); Break;
Case 'E': printf("0 to 59 \ n "); Break;
Default: printf ("beyond"); Break;
}
}
Printf ("thank you \ n");
Returns 0;
}
I hope it helps you. :)