Scanf for double not working in Dev C++

Question

I am having problem with floating point numbers. I think something is clashing here.

The output is :

Screenshot of the output

My code :

#include <stdio.h>


int main(){


    double y;

    printf("enter a decimal number: ");
    scanf("%f", &y);

    printf("%f\n", y);

    fflush(stdin);

    getchar();
    return 0;

    }

I am using Dev C++ 4.9.9.2 and first of all, I have to flush the carriage return out several times if it's not read previously . So if there is any alternative there then tell me. And secondly the output is giving this...

Don't use ancient IDEs (Dev-C++ 4.9.9.2 is from 2005) and don't use `fflush(stdin)` (it doesn't do what you think it does) — milleniumbug, Dec 26 '14 at 13:46
If you don't want other IDEs, there is at least a newer version of Dev-C++ (Orwell Dev-C++), which is actually maintained. — milleniumbug, Dec 26 '14 at 13:49
Why do you use a picture instead of simply pasting the text? — Deduplicator, Dec 26 '14 at 13:55
unable to copy the exact output. couldn't select. that's why. — nick, Dec 26 '14 at 14:01
so you should also ask about how to select and do copy pasting from cmd of windows..my friend.. @nick — Sumit Singh, Dec 26 '14 at 14:59
Possible duplicate of [scanf not working. need to read double from console](https://stackoverflow.com/questions/9860615/scanf-not-working-need-to-read-double-from-console) — phuclv, Sep 09 '18 at 04:26

Iharob Al Asimi · Accepted Answer · 2014-12-26T13:50:59.813

3

Use

scanf("%lf", &y);

instead. Since scanf("%f", &y); works for floats only.

If you enable compiler warnings it would tell you that the format specifier "%f" expects a float * and not double * argument.

edited Dec 26 '14 at 13:50

answered Dec 26 '14 at 13:45

Iharob Al Asimi

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thanks but what will I do if the carriage return is not read earlier. as I mentioned the problem.? – nick Dec 26 '14 at 13:48
1

I don't know what you mean, `scanf` will ignore all whitespace characters and hence it will block until input has non whitespace characters. – Iharob Al Asimi Dec 26 '14 at 13:53
`fflush(stdin)` has undefined behavior too. – Deduplicator Dec 26 '14 at 13:58

score 2 · Answer 2 · answered Dec 26 '14 at 13:47

2

Using wrong format specifier invoke undefined behavior and that's why you are getting unexpected result. Once UB is invoked, you may either get expected or unexpected result. Nothing can be said.
Use %lf to read double type data.

answered Dec 26 '14 at 13:47

haccks

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Spikatrix · Answer 3 · 2014-12-26T13:51:06.603

1

You are using the wrong format specifier in the scanf and doing this will result in UB(Undefined Behaviour).The correct format specifier for a double is %lf while that of a float is %f. So Just change your scanf to

scanf("%lf",&y);

edited Dec 26 '14 at 13:51

answered Dec 26 '14 at 13:45

Spikatrix

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µtex · Answer 4 · 2014-12-26T13:52:09.960

1

You should use

scanf("%lf", &y);

edited Dec 26 '14 at 13:52

answered Dec 26 '14 at 13:46

µtex

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Scanf for double not working in Dev C++

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