This is a GPA calculator that was programmed using the C programming language. The program ask the user for as many grades as the user wishes to calculate, and calculate the final gpa for the grades entered. 

#include <stdio.h>
#include <string.h>
#include <conio.h>


int main(int argc, char *argv[])
{

	const double A = 4.0;
	const double A_MINUS = 3.67;
	const double B_PLUS = 3.33;
	const double B = 3.0;
	const double B_MINUS = 2.67;
	const double C_PLUS = 2.33;
	const double C = 2.0;
	const double C_MINUS = 1.67;
	const double D = 1.00;
	const double F = 0.0;

	char lettergrade[25];
	double credit;
	double caltimes = 0;
	double totalcal = 0;
	double totalcredit = 0;
	double finalgpa = 0;
	int option;

	for (;;)
	{
		printf("\nEnter letter grade: ");
		scanf("%s",lettergrade);
		
		printf("Enter the course credit: ");
		scanf("%d", &credit);


		if (lettergrade == "a" || lettergrade == "A")
		{
			caltimes = credit * A;
		}
		else if (lettergrade == "a-" || lettergrade == "A-")
		{
			caltimes = credit * A_MINUS;
		}
		else if (lettergrade == "b+" || lettergrade == "B+")
		{
			caltimes = credit * B_PLUS;
		}
		else if (lettergrade == "b" || lettergrade == "B")
		{
			caltimes = credit * B;
		}
		else if (lettergrade == "b-" || lettergrade == "B-")
		{
			caltimes = credit * B_MINUS;
		}
		else if (lettergrade == "c+" || lettergrade == "C+")
		{
			caltimes = credit * C_PLUS;
		}
		else if (lettergrade == "c" || lettergrade == "C")
		{
			caltimes = credit * C;
		}
		else if (lettergrade == "c-" || lettergrade == "C-")
		{
			caltimes = credit * C_MINUS;
		}
		else if (lettergrade == "d" || lettergrade == "D")
		{
			caltimes = credit * D;
		}
		else if (lettergrade == "f" || lettergrade == "F")
		{
			caltimes = credit * F;
		}
		else
		{
			printf("Invaild Input...");
		}


		totalcredit = totalcredit + credit;
		totalcal = totalcal + caltimes;

		printf("Do you want to enter another grade (1 - Yes, 2 - no): ");
		scanf("%d",&option);
		if (option == 1)
		{
			continue;
		}
		else
		{
			break;
		}
	}

	finalgpa = totalcal / totalcredit;
	printf("Student's GPA: %f\n", finalgpa);


	return 0;
}