need help on simple c program compiled by gcc

hi redhat linux users:


I am using MAC osx 's gcc to compile a simple program

but it can not run(not run as I intended)

#include <stdio.h>
#include <math.h>
int main() {
double x1, y1;
printf("please enter floating number\n\n");
scanf(y1);
x1 = sin(y1);
printf("x1 = ", x1, " \n");
return 0;
}
---------------------------------------------------------------------
$ ./a.out
please enter floating number

x1 =
-------------------------------------
I just like to read a double y1, then printout x1 which equal sin(y1)

please help why it did not work by that way
eric

Dear Eric,

On May 7, 9:57 am, fs....TakeThisOut@yahoo.com wrote:
> hi redhat linux users:
>
>   I am using MAC osx 's gcc to compile a simple program

and why if you are using OS X are asking a RedHat group?
In fact this has nothing to do with the system: it's a C problem
should go to a C group.

>   but it can not run(not run as I intended)
>
>   #include <stdio.h>
> #include <math.h>
> int main() {
>   double x1, y1;
>   printf("please enter floating number\n\n");
>   scanf(y1);
>   x1 = sin(y1);
>   printf("x1 = ", x1,  " \n");
>   return 0;}
>
> ---------------------------------------------------------------------
> $ ./a.out
> please enter floating number
>
> x1 =
> -------------------------------------
> I just like to read a double y1, then printout x1 which equal sin(y1)

This is not what happens with the code you supplied:

../test.c: In function ‘main’:
../test.c:7: error: incompatible type for argument 1 of ‘scanf’

if you then read the manual page for scanf (man scanf) you see:

int scanf(const char *format, ...);

You have to supply the format:

scanf("%lf", &y1);

Note that you have to specify a pointer (a memory location where scanf
will write the result).

Your printf line is also wrong:

int printf(const char *format, ...);

Then:

printf("x1 = %f\n", x1);

You specify a format string (just one with placeholders) and then the
list of substitution variables.

> please help why it did not work by that way
> eric

Please ask to a C group but I think that you should get some more
programming/C knowledge before starting to code

In any case run the compiler with -Wall: it will generate warnings

Matteo