input in C programming language - c

Question

I want code receive from user a floating number but store only two digit after decimal point
for example if user input
a=123.123456789
a value will equal 123.12
#include <stdio.h>
int func(int x,int digit,int con,char* s)
{
int v;
v=x/digit;
v=v*digit;
x-=v;
if(con==1){
printf("%d %s(s) de R$ %.2f\n",(v/digit),s,(float)digit/100);
return x;
}
printf("%d %s(s) de R$ %.2f\n",(v/digit),s,(float)digit);
return x;
}
int main() {
int x=0;
float y;//if change to double the result will be true
scanf("%f",&y);
//y = ((int)(100.0 * y)) / 100.0;
x=(int)y;
y=y-x;
printf("NOTAS:\n");
char* arr="nota";
x=func(x,100,0,arr);
x=func(x,50,0,arr);
x=func(x,20,0,arr);
x=func(x,10,0,arr);
x=func(x,5,0,arr);
x=func(x,2,0,arr);
printf("MOEDAS:\n");
arr="moeda";
x=func(x,1,0,arr);
//mod
x=y*100;
x=func(x,50,1,arr);
x=func(x,25,1,arr);
x=func(x,10,1,arr);
x=func(x,5,1,arr);
x=func(x,1,1,arr);
return 0;
}
problem will found in:
https://www.urionlinejudge.com.br/judge/en/problems/view/1021

Answer 1

If you just want to round off to two decimal points you could try something like:
a = ((int) (a*100))/100.0;

Answer 2

The value have only 2 decimal places is a matter of displaying it, so you just need to print the number of decimal places you are interested in, like
float value = 123.123456;
printf("%.2f\n", value);
if you want to dynamicaly specify that number, you can use
float value = 123.123456;
int decimals = 2;
printf("%.*f\n", decimals, value);
If you want to store the value as a string then use sprintf() or better snprintf().
And taking the input with only two decimals does not make sense anyway because the output is what should be filtered instead of the input, note that after all you will ignore the extra decimals inserted by the user.
Also, note that floating point numbers cannot store exact numbers, so even i you leave only two decimal places by doing something like
float value = ((int)(100.0 * 123.1234156)) / 100.0
the actual value that is stored might be
123.1200000001
which has more decimal places.
One thing that you could try is
struct RealNumber
{
int integerPart;
int decimalPart;
};
and then handle the input to read them separately, which will be really dificult.