Lommeregner i C

Kode 

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

#define BUFSIZE 100

int main(void)
{
  char ch = 0;
  char count = 0;
  char counta = 0;

  char regnetegn;
  char buffer[BUFSIZE];
  char tala[BUFSIZE];

  float a, b, result;
  for( count = 0; count < BUFSIZE; count++)
  {
    buffer[count] = '\\0';
    tala[count] = '\\0';
  }
  count = 0;
  clrscr();
  printf("Input a string:");
  gotoxy(1,2);

  // Indtast tal i buffer
  while (ch != '\\r')
  {
    ch = getch();
    if (ch == '\\b')
    {
      putch(ch);
      putch(' ');
      if (count != 0)
      {
        count--;
      }
    }
    else
    {
      if (ch != '\\r')
      {
        buffer[count++] = ch;
      }
    }
    putch(ch);
    if (count == BUFSIZE)
    {
      count = 0;
    }
  }

  // Sorter tal i 2 buffer
  count = 0;
  counta = 0;
  while (buffer[count] != '\\0')
  {
    if( (buffer[count] >= '0') && (buffer[count] <= '9'))
    {
      tala[counta++] = buffer[count++];
    }
    else if( (buffer[count] == ',') || (buffer[count] == '.'))
    {
      tala[counta++] = buffer[count++];
    }
    else
    {
      switch (buffer[count])
      {
        case '+': regnetegn = buffer[count]; break;
        case '-': regnetegn = buffer[count]; break;
        case '*': regnetegn = buffer[count]; break;
        case '/': regnetegn = buffer[count]; break;
        default: regnetegn = '\\0'; break;
      }
      count++; // skip regnetegnet
      a = strtod(tala, 0); // konverter foerste tal
      memset(tala, 0, sizeof(tala)); // goer tala klar til at gemme naeste tal
      counta = 0;
    }
  }
  b = strtod(tala, 0); // konverter andet tal

  // udregn
  switch(regnetegn)
  {
    case '+': result = a + b; break;
    case '-': result = a - b; break;
    case '*': result = a * b; break;
    case '/': result = a/b; break;
  }
  // udskriv
  printf("%f %c %f = %f\\n", a, regnetegn, b, result);
  return 0;
}