Computing the average of grades in C - c

Question

I have write a program that allows me to firstly enter a character c followed by an integer n and n float values representing grades. Using array to store the grades I have entered and no more than 100 grades can be introduced. The program allowed me to calculate the sum of the elements in array when I enter 's', compute the production of the elements in array when i enter 'p' and compute the average of the element s when i enter other words. After i enter the grades and character. The program has no response when i hit return to continue. So where is the mistake in my code
#include<stdio.h>
#include<stdio.h>
int main()
{
char c;
int integer_grade [100];
float floting_grade [100];
printf("Enter a grade");
scanf("%i,%f",&integer_grade[100],&floting_grade[100]);
int *a;
a=&integer_grade[100];
int *b;
b=&floting_grade[100];
printf("Enter a character");
getchar();
scanf("%c",&c);
int n;
switch(c)
{
case 's':
for (n=0;n=100;n++)
*a+=*a;
*b+=*b;
printf("Sum is %d",*a+*b);
case 'p':
for (n=0;n=100;n++)
*a*=*a;
*b*=*b;
printf("Sum is %d",*a**b);
default:
for (n=0;n=100;n++)
*a+=*a;
*b+=*b;
printf("average is %d",(*a+*b)/100);
}
return 0;
}
The task is:
Write a program where you first enter a character c followed by an integer n and n float values representing grades. Use an array for storing the grades. You can assume that not more than 100 grades would be introduced. Yours program should compute and print the following: if c is 's' the sum of the grades, if c is 'p' the product of all grades and if another character was introduced then the arithmetic mean of all grades.
*use switch
*you can safely assume thee input will be valid.

Answer 1

Thoughts.
This is undefined behavior. You are assigning the read integer and float to offset 100 in those arrays, which doesn't exist.
int integer_grade[100];
float floting_grade[100];
scanf("%i,%f", &integer_grade[100], &floting_grade[100]);
These pointers point to memory that is outside the bounds of their respective arrays.
int *a = &integer_grade[100];
int *b = &floting_grade[100];
You ask for a character and then you ignore the value of that character:
getchar();
You then follow that up by getting the following character. Which is odd. But you do use the correct type and what not. So that's a win.
scanf("%c",&c);
Your indentation in these for loops implies that you think that both statements will be iterated on as part of the loop. That's incorrect. Use { ... } to accomplish that:
for (n=0;n=100;n++)
*a+=*a;
*b+=*b;
I have no idea what you think you're accomplishing by *a += *a. I do know that the value at *a is going to grow quite quickly (and will likely overflow).
Switch statements use fallthrough on the cases. That means that if your case is 's', it will run all of the code in the switch statement, including all three cases. If you don't want this behavior, you should place break statements at the end of each case.
Please go back to your book / faculty / internet resource and read how a for loop works. This doesn't do what you probably think it does. In fact, this is an infinite loop!
for (n=0; n=100; n++)

Answer 2

Whatever do you try to do here, it's not right at all.
First: You declare 2 arrays of 100 elements, THEN you assign values outside of that array bounds (100 element array start from 0, finishes at 99)
Second: You create 2 pointers that points to outside of those array bounds.
Third: Inside the switch , the for (n=0;n=100;n++) is wrong, it should be something like for(n = 0; n < 100; n++)
Fourth: This
for (n=0;n=100;n++)
*a+=*a;
*b+=*b;
it would increment (if that for would be correct) only the first statement.
Correct way would be
for (n = 0; n < 100; n++)
{
*a += *a;
*b += *b;
}
Proper code would be
#include <stdio.h>
int main()
{
char c;
int integer_grade[100];
float floting_grade[100];
int nr_of_grades;
int i = 0;
printf("Enter number of grades: ");
scanf("%d", &nr_of_grades);
for(i = 0; i < nr_of_grades; i++)
{
printf("Enter a int grade: ");
scanf("%d", &integer_grade[i]);
printf("Enter a float grade: ");
scanf("%f", &floting_grade[i]);
}
int operation_i = 0;
float operation_f = 0;
printf("Enter a character");
scanf(" %c", &c);
int n;
switch(c)
{
case 's':
for (n = 0; n < nr_of_grades; n++)
{
operation_i += integer_grade[n];
operation_f += floting_grade[n];
}
printf("Sums are Int: %d Float: %f", operation_i, operation_f);
case 'p':
operation_i = 1;
operation_f = 1;
for (n = 0; n < nr_of_grades; n++)
{
operation_i *= integer_grade[n];
operation_f *= floting_grade[n];
}
printf("Products are Int: %d Float: %f", operation_i, operation_f);
default:
for (n = 0; n < nr_of_grades; n++)
{
operation_i += integer_grade[n];
operation_f += floting_grade[n];
}
printf("Average is Int: %d Float: %f", operation_i / nr_of_grades, operation_f / nr_of_grades);
}
return 0;
}