Calculadora Faculdade

#include <stdio.h>
#include <stdlib.h>
#include <locale.h>

enum  {
    SUM      = '+',
    MULT     = '*',
    SUB      = '-',
    DIVISION = '/'
} ;

float total = 0;
int op_n = 1;
int main()
{
    char operation = '+';

    float var1 = 0;
    float var2 = 0;


    printf("Olaa Usuario !\n Voce precisa inserir os dados no padrao.\n1.5+25\n\nOu Semelhante.\n\n");

    scanf("%f%c%f", &var1,&operation,&var2 );
    char selected ;

    while(1){
        if(total != 0){
            scanf("%c%f", &operation,&var2 );
        }
        switch(operation){

            case '+':
                selected = SUM;
                break;
            case '-':
                selected = SUB;
                break;
            case '/':
                selected = DIVISION;
                break;
            case '*':
                selected = MULT;
                break;
            default:
                    printf("Informe corretamente a operação");
                    exit(1);
        }
        if(total != 0){
            calcular(selected, &total, &var2);

        } else {
            calcular(selected, &var1, &var2);
        }
    }
    return 0;
}

void calcular(char sel, float *var1, float *var2){

    switch( sel ){
        case SUM:
            total = (*var1 + *var2);
            break;
        case SUB:
            total = (*var1 - *var2);
            break;
        case MULT:
            total = (*var1 * *var2);
            break;
        case DIVISION:
            total = (*var1 / *var2);
            break;
    }
    op_n++;
    fflush(stdin);


    printf("%4.2f %1c %4.2f = %.2f\n", *var1, sel, *var2, total);
}