To read an integer we use either %d and %i format strings, but to read a float we use %e, %f, and %g format strings of type double
to be sure,
of course, Let’s deconstruct some examples
The %f format string
to explain, Well, imagine this
To begin with, suppose, we have a float variable a=32 and, at that instant, we would like to print variable a with %f format string
float a=32.0f; printf("%f",a); //result 32.000000
Guess what the output will be?
unquestionably, The answer is 32.000000
But wait!
at this instant, Why does the output have 6 fractional digits?
as can be seen, The %f format string will always display the floating point variable in a fixed decimal format which means it will always have a fraction part which is by default six (.000000)
with this intention,32 will become 32.000000,
in a word,
The %e format string
The %e format string will always display the floating point variable in exponential format
float a=32.0f; printf("%e",a);// the result is 3.200000e+001
as i have shown, if we use %e we get the answer as 3.200000
undoubtedly, the 200000 is the default 6-fraction digits
But why
Because we right-shifted the decimal point by one digit right
Number | exponential notation | scientific notation |
---|---|---|
1000 | 1e3 | 1×103 |
1000000 | 1![]() | 1x![]() |
1000000000 | 1![]() | 1x![]() |
The %g format string
The %g format string can display the floating point variable in either exponential format or fixed decimal format
At the same time, how %g decide to display exponential format or fixed decimal format?
at this point, It all depends upon the floating-point variable size
In short, it switches to exponential format when a floating point variable exponent is less than -4(that is, 0.0004=4x=4
) or greater than the precision(which is by default 6) such as[1234567]
Trailing zeros and trailing decimal point are not printed
float a=32.0f; printf("%g",a); // the result is 32
Have you noted, to point out, the % g format string is not displaying the trailing zeros of 32
whereas the %f format string can display the trailing zero of 32.000000 and on this occasion, it is not possible with the %g format string
until now, okay,
the %f format string can displays 32.23 as 32.230000 but the %g format string can displays the 32.23 as 32.23(the trailing zeros are neglected)
Furthermore, you can print the trailing zeros and trailing decimal point with %g format string only in case, when you use the #flag
float a=32.0f; printf("%#g",a); // the result is 32.0000
if the floating variable is too large or too small then, at that instant, the %g format string switches to the exponential format
so, that variable adjust itself with fewer characters
float a=321224587.23f; printf("%g",a); // the result is 3.21225e+008
On one hand, To read and print the double value with %g format string
Use l(ell) with scanf for %g format string(%lg) and the l(ell) will not have any effect on printf function with %g format string
double a=32.23; double b; printf("enter the value of B\n"); scanf("%lg",&b); printf("VALUE of a= %g\n",a); // the result is 32.23 printf("VALUE of b= %g\n",b);
On the other hand, in C99 to read and write the type of long double use the letter L in front of the %g format string
long double a=32.23; scanf("%Lf",&a); printf("VALUE of a= %Lg\n",a);
For instance, if you use the C89 version of C then the effect of using conversion specifications %g and %G is undefined but, it is illegal in C99
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