Another example for if condition

Write a program which can calculate letter grate point of a student after getting marks from key board.

 #include<stdio.h>

 #include<conio.h>

 main(){

   int marks,i;

   printf("\nGive your number = ");

   scanf("%d",&marks);

   if(marks<0 || marks >100){

     printf("It is error number");

   }

   if(marks >= 0  && marks < 33){

     printf("The letter grade is = F");

   }

   if(marks >= 33  && marks < 40){

     printf("The letter grade is = D");

   }

   if(marks >= 40  && marks < 50){

     printf("The letter grade is = C");

   }

   if(marks >= 50  && marks < 60){

     printf("The letter grade is = B");

   }

   if(marks >= 60  && marks < 70){

     printf("The letter grade is = A-");

   }

   if(marks >= 70  && marks < 80){

     printf("The letter grade is = A");

   }

   if(marks >= 80  && marks <= 100){

     printf("The letter grade is = A+");

   }

   getch();

 }