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Asked: 2026-05-25T12:29:15+00:00

I’m looking through the source code of a project written in C. Here is

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I’m looking through the source code of a project written in C. Here is a list of options that are defined (no these aren’t the real defines…not very descriptive!)

...
#define OPTION_5    32768
#define OPTION_6    65536
#define OPTION_7    0x20000L
#define OPTION_8    0x40000L
#define OPTION_9    0x80000L

I’d like to add a new option OPTION_10 but before I do that, I’d like to understand what exactly the hex numbers represent?

Do these numbers convert to the expected decimal values of 131,072 262,144 524,288 ? If so, why not keep the same format as the earlier options?

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  1. Editorial Team

    Do these numbers convert to the expected decimal values of 131,072

    Yes. You can use Google for the conversion: search for “0x20000 in decimal“.

    If so, why not keep the same format as the earlier options?

    I guess simply because programmers know their powers of two up to 65536 and prefer hexadecimal, where they are more recognizable, above that.

    The L suffix forces the literal constant to be typed at least as a long int, but the chosen type may be still larger if that’s necessary to hold the constant. It’s probably unnecessary in your program and the programmer used it because s/he didn’t understand the emphasized clause. The nitty-gritty details are in 6.4.4.1, page 56 of the C99 standard.

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