Question

I tried to write a simple c program that does something with derivatives, but that’s not the point of the question:
When I run the program, It asks me to input a bunch of floating point values, but it doesn’t matter what I input the scanf function will always assign “junk” values to the variables, here’s the code:

double a, b, c, d, x, h;
printf("Please enter the coefficient of X cubed: ");
scanf("%3f", &a);
printf("\nPlease enter the coefficient of X squared: ");
scanf("%3f", &b);
printf("\nPlease enter the coefficient of X: ");
scanf("%3f", &c);
printf("\nPlease enter the free coefficient: ");
scanf("%3f", &d);
printf("\nPlease enter x: ");
scanf("%3f", &x);
printf("\nPlease enter the offset: ");
scanf("%3f", &h);

printf("%.3f %.3f %.3f %.3f %.3f %.3f", a,b,c,d,x,h);

I enter the values for a, b, c, d, x and h, but the printf function shows really weird values – completely different from what I entered.

I googled it in every possible way I thought of, and I can’t seem to find the reason it happens.

Can someone try to figure out why it happens?

Answer 1

Use lf conversion specifier to read double values and not f conversion specifier which is specifief to read float values. fscanf and fprintf functions are not symmetrical in that respect.