Calculator using getchar, putchar

[arlen20002000]

Hi. I need help for a school project. I need to creat a calculator program using only getchar and putchar. the user has to enter the statement and the program should echo the statement and the answer. for example the user has to enter " 3 + 6 " and the program should answer " 3 + 6 = 9".
I appreciate any help.

here is what I have. and I have no idea what's wrong.

#include <stdio.h>
#include <math.h>
char Cont (void);
int isdigit1 (char C);
int Convert(char );
int main(void)
{
 int Error = 0 , Num1 , Num2, Oper;
 char Flag, c;
 double Result;
 do
 {
  while ( ( c=getchar() ) != EOF)
  {
   if ((c == ' ') || (c = '\t'))
   {
    putchar(c);
    continue;
   }
 
   if /*while*/ (isdigit1 (c))
   {
    Num1 = Convert(c);
   } 
   if ((c=='+') || (c=='-') || (c=='*') || (c=='/') || (c=='%'))
   {
    switch (c) 
    {
    case '+':
     Oper = 1; // current month days
     break;
 
    case '-': 
     Oper = 2;
     break;
 
    case '*': 
     Oper = 3;
     break;
 
    case '/': 
     Oper = 4;
     break;
 
             case '%': 
     Oper = 5;
     break;
    }
    putchar (c);
   }
 
   if /*while*/ (isdigit1 (c))
   {
    Num2 = Convert(c);
   }
 
   switch (Oper)
   {
   case 1:
    Result = (double)(Num1 + Num2);
    break;
 
   case 2:
    Result = (double)(Num1 - Num2);
    break;
 
   case 3:
    Result = (double)(Num1 * Num2);
    break;
 
   case 4:
    Result = (double)(Num1 / Num2);
    break;
 
   case 5:
    Result = (double)(Num1 % Num2);
    break;
   }
   printf (" = %.2f", Result);
 
   Flag = Cont();
  }
 }while ((Flag == 'y') || (Flag == 'Y') ); 
 return 0;
}
 
int Convert (char  c)
{
 int ch,
  sum = c - '0';
 while ((( ch = getchar() ) != ' ' ) && (ch != '\n' ))
 {
  if ( !isdigit1 (ch) )
   break;
  sum = sum *10 + ( ch - '0');
  putchar(ch);
 }
 return (sum);
}
int isdigit1 (char C)
{
 if ((C>= '0') && (C<= '9'))
  return 1;
 return 0;
}
char Cont ()
{
 char Flag;
 printf ("******************\nWould you like to continue?\nEnter y for yes, Anything else for no.\n");
 scanf ("%c%*c", &Flag);
 return Flag;
}

[Dino]

I think you do have an idea what is wrong. It will either compile, or it won't. If it compiles, it will either work, or it won't. If it doesn't compile, chances are the compiler is producing messages, etc...

Please provide more information. (Of course, all 200 people who frequent this forum and are active posters could create a new project with your code to answer these questions for themselves, but how much sense does that make?

Please ask an intelligent question.

Todd

[arlen20002000]

ok. let's make it intelligent!! It does compile with no error, but it doesn't work. somewhere my code has a problem.

[QuantumPete]

ok. let's make it intelligent!! It does compile with no error, but it doesn't work. somewhere my code has a problem.

Clearly. But if you gave us more specific information on what doesn't work. What error messages, if any, you get. Whether the output is just wrong or the program crashes. That'll help us save our telepathy powers for the really intractable bugs.

QuantumPete

[vart]

getchar returns int - so c should be int

			if (isdigit1 (c))
			{
				Num1 = Convert(c);
			} 

			...

			if (isdigit1 (c))
			{
				Num2 = Convert(c);
			}

So could you provide a scenario when this code will initilize Num1 and Num2 on different iterations of the loop?

[JDGATX]

while ( ( c=getchar() ) != EOF)

The program gets hung up in the first inner while loop.

if ((c == ' ') || (c = '\t'))

This conditional is always triggered, no matter what you input.