C conversion specifiers and modifiers
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A handy reference to C conversion specifiers and modifiers
In this post I want to create a helpful reference for all the C conversion specifiers you can use, commonly with printf()
, scanf()
and similar I/O functions.
Specifier | Meaning |
---|---|
%d / %i | Signed decimal integer |
%u | Unsigned decimal integer |
%c | Unsigned char |
%s | String |
%p | Pointer in hexadecimal form |
%o | Unsigned octal integer |
%x / %X | Unsigned hexadecimal number |
%e | Floating point number in exponential format in e notation |
%E | Floating point number in exponential format in E notation |
%f | double number in decimal format |
%g / %G | double number in decimal format or exponential format depending on the value |
In addition to those specifiers, we have a set of modifiers.
Let’s start with digits. Using a digit between %
and the format specifier, you can tell the minimum field width. Example: %3d
will take 3 spaces regardless of the number printed.
This:
printf("%4d\n", 1);
printf("%4d\n", 12);
printf("%4d\n", 123);
printf("%4d\n", 1234);
should print
1
12
123
1234
If you put a dot before the digit, you are not telling the precision: the number of decimal digits. This of course applies to decimal numbers. Example:
printf("%4.2f\n", 1.0);
printf("%4.3e\n", 12.232432442);
printf("%4.1e\n", 12.232432442);
printf("%4.1f\n", 123.22);
will print:
1.00
1.223e+01
1.2e+01
123.2
In addition to digits, we have 3 special letters: h
, l
and L
.
h
, used with integer numbers, indicates ashort int
(for example%hd
) or ashort unsigned int
(for example%hu
)l
, used with integer numbers, indicates along int
(for example%ld
) or a long unsigned int (for example%lu
).L
, used with floating point numbers, indicates along double
, for example%Lf
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