Why wont the following 'C' code work?

Question

Hello, I have recently begun learning the 'C' programming language and tried (and failed so far) to create a basic calculator program..
What is wrong with the following code and are there any helpful tips or anything people can help me with??

#include

int math_function(int x, int y);

int main()
{
int x, y;
char sign;
printf("Choose:\n");
printf("a) Addition\n");
printf("b) Subtraction\n");
printf("c) Division\n");
printf("d) Multiplication\n");
scanf("%c", &sign);

printf("Enter two numbers:\n");
scanf("%d%d", &x, &y);

/*Print out their numbers inside the math_function*/
printf("%d\n", math_function(x, y));
return;
}
char sign;
int math_function(int x, int y)
{
switch(sign)
{
case 'a':
return x + y;
break;
case 'b':
return x - y;
break;
case 'c':
return x / y;
break;
case 'd':
return x * y;
break;
/*Default statement*/
default:
printf("You entered an invalid choice\n");
}
}


Thanks!

Answer 1

Hi,



You've done ok, but just need a couple of errors repaired.



As the previous person mentioned, you really need to use global variables:

  These are declared along with your #include's before int main()



You also needed to remove the math_function you left up there with the #includes



Your switch statement could be left as is, but I've made a modification there in the code below, to remove the redundant break's (redundant because you broke anyway using the return), and changed the default: to break; only to avoid printing your Error message with a stray decimal value appearing at end of message. This is dealt with in the main() using an if () else.



Both main() and math_function() do need a return 0 also, as you'll see below.



#include

// Global Variables useable in main and function

char sign;

int x, y;



int main() {

  printf("Choose:\n");

  printf("a) Addition\n");

  printf("b) Subtraction\n");

  printf("c) Division\n");

  printf("d) Multiplication\n");

  scanf("%c", &sign);



  printf("Enter two numbers:\n");

  scanf("%d%d", &x, &y);



  /*Print out their numbers inside the math_function*/

  /* This if else allows the math_funtion to print the values for a, b, c or d choices

   * but any other choice just print the error message so that value does not

   * stray to right side of message

   */

  if (sign == 'a' || sign == 'b' || sign == 'c' || sign == 'd')

    printf("%d\n", math_function(x, y));

  else

    printf("'%c' is an invalid choice ", sign);

  return 0;

}



int math_function(int x, int y) {

  switch(sign) {

    case 'a':

      return x + y;

    case 'b':

      return x - y;

    case 'c':

      return x / y;

    case 'd':

      return x * y;

    default:

      break;

  }

  return 0;

}

Answer 2

I fixed some things....

untested code follows.....



#include



int math_function(int , int ,int );



int main()

{

int x, y;

char operator;

printf("Choose:\n");// better just to let the user punch in the operator rather than abcd ...

printf("+ Addition\n");

printf("- Subtraction\n");

printf("/ Division\n");

printf("* Multiplication\n");

scanf("%c", &operator);



printf("Enter two numbers:\n");

scanf(" %d %d", &x, &y);// the spaces tell scanf to ignore white space twixt the numbers



/*Print out their values returned from the math_function*/

printf("%d\n", math_function(x, y, operator));// better practice to pass the operator here rather than as a global

return 0;

}

// char sign; do not redefine sign as a global -- pass the operator into the function -- better practice

int math_function(int x, int y, int op) // believe it or not '+' is an int (integer) constant in C and has the sizeof an int

{

switch(op)

{

case '+':

return x + y;

break;

case '-':

return x - y;

break;

case '/':

if(y!=0)

return x / y;

else

printf("you cannot do that !");

break;

case '*':

return x * y;

break;

/*Default statement*/

default:

printf("You entered an invalid choice\n");

}

return 0;// you still need a return value here :-)

}

Answer 3

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Answer 4

First of all define your 'sign' variable as global.

main function: You should return a value (eg: return 0;)

math_function: You should return a value.



Also, your code could be improved a lot.

Answer 5

u missed a colon