--- title: printf TARGET DECK: Obsidian::STEM FILE TAGS: c17::printf tags: - c17 - printf --- ## Overview The syntax for the format placeholder is `%[flags][width][.precision][length]specifier`. %%ANKI Basic What four optional parts make up a `printf` argument? Back: Flags, width, precision, and length. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1708974221761--> END%% %%ANKI Basic What is the purpose of the width field in a `printf` argument? Back: It specifies a minimum number of characters to ouput. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1732285301746--> END%% %%ANKI Basic What is the purpose of the precision field in a `printf` argument? Back: It specifies the maximum limit on the output, depending on the argument type. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1732285301754--> END%% %%ANKI Basic What is the purpose of the length field in a `printf` argument? Back: It specifies the size of the `printf` argument before default promotion. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1732285301762--> END%% %%ANKI Basic Which header file contains basic `printf` functionality? Back: `<stdio.h>` Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1708384441467--> END%% %%ANKI Cloze {1:`width`} specifies a {2:minimum} while {2:`precision`} specifies a {1:maximum}. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1708384441472--> END%% %%ANKI Cloze The {1:`width`} and {1:`precision`} fields are output related whereas the {2:`length`} field is input related. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1708425941269--> END%% ## Flags | Flag | Description | | ---- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | `-` | Left-aligns the output | | `+` | Prepends a plus for positive signed-numeric types | | `␣` | Prepends a space for positive signed-numeric types | | `0` | Prepends zeros for numeric types | | `#` | For `g` and `G`, trailing zeros are not removed. For `f`, `F`, `e`, `E`, `g`, and `G`, output always has a decimal point. For `o`, `x`, and `X`, the text `0`, `0x`, and `0X` is prepended to nonzero numbers respectively. | %%ANKI Cloze The {`-`} flag {left-aligns} the output. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1707918756812--> END%% %%ANKI Basic What is the output of `printf("%-2d abc", 100)`? Back: `100␣abc` Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1708384441477--> END%% %%ANKI Basic What is the output of `printf("%-4d abc", 100)`? Back: `100␣␣abc` Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1708384441481--> END%% %%ANKI Basic What is the output of `printf("%.4d abc", 100)`? Back: `0100␣abc` Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1708384441486--> END%% %%ANKI Basic What is the output of `printf("%04d abc", 100)`? Back: `0100␣abc` Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1708384441491--> END%% %%ANKI Basic What is the output of `printf("%.4s abc", "efg")`? Back: `efg␣abc` Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1708384441495--> END%% %%ANKI Basic What is the output of `printf("%.2s abc", "efg")`? Back: `ef␣abc` Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1708384441499--> END%% %%ANKI Basic What is the output of `printf("%.2f abc", 0.01234)`? Back: `0.01␣abc` Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1708384441503--> END%% %%ANKI Basic How does the precision field affect `"%s"` parameters? Back: Strings are truncated if longer than the specified precision. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1708384441507--> END%% %%ANKI Basic How does the precision field affect `"%f"` parameters? Back: Decimal values are truncated if longer than the specified precision. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1708384441511--> END%% %%ANKI Basic What does a negative width field value indicate? Back: This is actually a positive width with a `-` (left-align) flag. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1708384441515--> END%% %%ANKI Basic The `-` `printf` flag overrides what default behavior? Back: Output is right-aligned by default. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1707918756840--> END%% %%ANKI Cloze The {`+`} `printf` flag {prepends a plus for positive signed-numeric types}. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1707918756846--> END%% %%ANKI Basic The `+` `printf` flag overrides what default behavior? Back: Nothing is prepended to positive signed-numeric types by default. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1707918756852--> END%% %%ANKI Cloze The {`␣`} `printf` flag {prepends a space for positive signed-numeric types}. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1707918756856--> END%% %%ANKI Basic The `␣` `printf` flag overrides what default behavior? Back: Nothing is prepended to positive signed-numeric types by default. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1707918756861--> END%% %%ANKI Basic How do the `+` and `␣` `printf` flags relate to one another? Back: Both prepend a character to positively signed-numeric types. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1707918756865--> END%% %%ANKI Basic What happens if both the `+` and `␣` `printf` flags are specified? Back: The `+` flag takes precedence. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1707918756870--> END%% %%ANKI Cloze The {`0`} `printf` flag {prepends zeros for numeric types}. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1707918756875--> END%% %%ANKI Basic What option must be specified for the `0` `printf` flag to take effect? Back: The "width" option. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1707918756881--> END%% %%ANKI Basic The `0` `printf` flag overrides what default behavior? Back: Spaces are used to match the "width" option by default. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1707918756888--> END%% %%ANKI Basic How is `%#g` different from `%g`? Back: The former always includes a decimal point and may include trailing `0`s. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1710673807973--> END%% %%ANKI Basic How is `%#f` different from `%f`? Back: The former always includes a decimal point. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1710673807976--> END%% %%ANKI Basic How is `%#e` different from `%e`? Back: The former always includes a decimal point. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1710673807979--> END%% %%ANKI Basic Which `printf` flag can be used to ensure decimal points in the output of floating-point types? Back: `#` Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1710673807981--> END%% %%ANKI Basic How is `%#o` different from `%o`? Back: The former prepends a `0` to the output. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1710673807983--> END%% %%ANKI Basic How is `%#x` different from `%x`? Back: The former prepends a `0x` to the output. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1710673807986--> END%% %%ANKI Basic How is `%#X` different from `%X`? Back: The former prepends a `0X` to the output. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1710673807988--> END%% %%ANKI Cloze `%#o` is to {`0`} as `%#x` is to {`0x`}. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1710673807990--> END%% ## Length Length | Description --------- | ----------- `hh` | `int` sized integer argument promoted from a `char` `h` | `int` sized integer argument promoted from a `short` `l` | `long` sized integer argument `ll` | `long long` sized integer argument `z` | `size_t` sized integer argument %%ANKI Basic *Why* do length modifiers for e.g. `char` exist? Back: For maximum portability in the face of default argument promotions. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1708426673637--> END%% %%ANKI Cloze The {`hh`} length corresponds to the {`char`} type declaration. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1708426673664--> END%% %%ANKI Cloze The {`h`} length corresponds to the {`short`} type declaration. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1708426673668--> END%% %%ANKI Cloze The {`l`} length corresponds to the {`long`} type declaration. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1708426673711--> END%% %%ANKI Cloze The {`ll`} length corresponds to the {`long long`} type declaration. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1708426673719--> END%% %%ANKI Cloze The {`z`} length corresponds to the {`size_t`} type declaration. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1708426673725--> END%% ## Specifiers Specifier | Description --------- | ----------- `d`, `i` | a decimal `signed int` `u` | a decimal `unsigned int` `x`, `X` | a hexadecimal `unsigned int` `o` | an octal `unsigned int` `f`, `F` | a `double` in fixed-point notation `e`, `E` | a `double` in standard notation `g`, `G` | a `double` in normal or standard notation `s` | a `NUL`-terminated string `c` | a `char` character `p` | `void*` address in an implementation-defined format %%ANKI Basic What character do `printf` format specifiers start with? Back: `%` Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1707852083029--> END%% %%ANKI Basic Why is `printf` named the way it is? Back: It stands for **print f**ormatted. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1707852083037--> END%% %%ANKI Cloze The {`%d` and `%i`} format specifers work on a {decimal `signed int`}. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1707852083040--> END%% %%ANKI Cloze {`%d` and `%i`} are to `signed` as {`%u`} is to `unsigned`. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1707852083044--> END%% %%ANKI Cloze The {`%u`} format specifier outputs a {decimal `unsigned int`}. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1707852083047--> END%% %%ANKI Basic What distinguishes format specifiers `%d` and `%i`? Back: Nothing. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1707852083050--> END%% %%ANKI Basic Which format specifiers were probably used to yield `printf` output `-12`? Back: `%d` or `%i` Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1707852083054--> END%% %%ANKI Basic What distinguishes format specifiers `%d` and `%u`? Back: The former is for signed integers, the latter unsigned. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1707852083058--> END%% %%ANKI Cloze The {`%x`} format specifier outputs a {lowercase hexadecimal `unsigned int`}. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1707852083063--> END%% %%ANKI Basic Which format specifier was probably used to yield `printf` output `7af`? Back: `%x` Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1707852083068--> END%% %%ANKI Cloze The {`%X`} format specifier outputs an {uppercase hexadecimal `unsigned int`}. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1707852083074--> END%% %%ANKI Basic Which format specifier was probably used to yield `printf` output `7AF`? Back: `%X` Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1707852083080--> END%% %%ANKI Basic What distinguishes format specifiers `%x` and `%X`? Back: The former outputs lowercase hex digits, the latter uppercase. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1707852083086--> END%% %%ANKI Cloze The {`%f`} format specifier outputs a {lowercase fixed-point `double`}. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1710450347005--> END%% %%ANKI Cloze The {`%F`} format specifier outputs an {uppercase fixed-point `double`}. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1710450347008--> END%% %%ANKI Basic What distinguishes format specifiers `%f` and `%F`? Back: The former outputs lowercase identifiers, the latter uppercase. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1710450347010--> END%% %%ANKI Basic What three special identifiers might specifier `%f` output? Back: `inf`, `infinity`, and `nan` Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1710450347012--> END%% %%ANKI Basic Assuming round-to-even, what is the output of `printf("%.0f", 3.5)`? Back: `4` Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016. <!--ID: 1710675908301--> END%% %%ANKI Basic Assuming round-to-even, what is the output of `printf("%.0f", 2.5)`? Back: `2` Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016. <!--ID: 1710675908304--> END%% %%ANKI Basic How does the C standard define the rounding mode of floating-point specifiers? Back: This is implementation specific. Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016. <!--ID: 1710675908306--> END%% %%ANKI Basic What does the rounding mode of floating-point specifiers refer to? Back: How numbers with greater than the specified precision are output. Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016. <!--ID: 1710675908307--> END%% %%ANKI Basic What three special identifiers might specifier `%F` output? Back: `INF`, `INFINITY`, and `NAN` Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1710450452444--> END%% %%ANKI Basic Which format specifier was probably used to yield `printf` output `inf`? Back: `%f` Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1710450347014--> END%% %%ANKI Cloze {1:Fixed-point} notation is to {2:`%f`} whereas {2:standard/exponential} notation is to {1:`%e`}. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1710450347015--> END%% %%ANKI Basic Which format specifier was probably used to yield `printf` output `172.345000`? Back: `%f` Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1710450347017--> END%% %%ANKI Basic What term describes the kind of output notation corresponding to `%f`? Back: Fixed-point notation. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1710450347018--> END%% %%ANKI Basic What distinguishes format specifiers `%e` and `%E`? Back: The former outputs an `e`, the latter an `E`. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1710450347020--> END%% %%ANKI Basic How many digits follow `e` in the output of `printf` specifier `%e`? Back: At least `2`. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1710450452447--> END%% %%ANKI Basic Which format specifiers correspond to scientific notation? Back: `%e` and `%E` Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1710556915108--> END%% %%ANKI Basic Which format specifier was probably used to yield `printf` output `1.723450e+02`? Back: `%e` Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1710450347022--> END%% %%ANKI Basic What is the default precision of `%f`? Back: `6` Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1710452502031--> END%% %%ANKI Basic What is the output of `printf("%e", 3.14)`? Back: `3.140000e00` Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1710450347023--> END%% %%ANKI Basic What is the output of `printf("%e", 314)`? Back: `3.140000e02` Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1710450347025--> END%% %%ANKI Basic What term describes the kind of output notation corresponding to `%e`? Back: Standard or exponential notation. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1710450347026--> END%% %%ANKI Basic What is the default precision of `%e`? Back: `6` Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1710452502034--> END%% %%ANKI Cloze The {`%g`} format specifier outputs a {lowercase `double` in fixed-point or standard notation}. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1710599835115--> END%% %%ANKI Cloze The {`%G`} format specifier outputs an {uppercase `double` in fixed-point or standard notation}. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1710844199536--> END%% %%ANKI Basic The `%g` format specifier subsumes functionality of what other format specifiers? Back: `%f` and `%e` Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1710599806326--> END%% %%ANKI Basic The `%G` format specifier subsumes functionality of what other format specifiers? Back: `%F` and `%E` Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1710599806328--> END%% %%ANKI Basic How does `%g` handle integral values differently from `%f`? Back: It excludes a trailing `.` and insignificant `0`s. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1710603411171--> END%% %%ANKI Basic How does `%g` handle non-integral values differently from `%f`? Back: It excludes insignifant `0`s after the decimal point. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1710603411174--> END%% %%ANKI Basic What distinguishes `%g` from `%G`? Back: The former uses lowercase letters. The latter uses uppercase letters. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1710599806331--> END%% %%ANKI Basic What is the output of `printf("%.1f", 2.0)`? Back: `2.0` Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1712836989972--> END%% %%ANKI Basic Assuming fixed-point notation, what is the output of `printf("%.1g", 2.0)`? Back: `2` Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1712836989975--> END%% %%ANKI Basic Assuming fixed-point notation, what is the output of `printf("%g", 3.14)`? Back: `3.14` Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1710599806333--> END%% %%ANKI Basic Assuming fixed-point notation, what is the output of `printf("%g", 3)`? Back: `3` Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1710599806334--> END%% %%ANKI Basic What is the output of `printf("%f", 3)`? Back: `3.000000` Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1710599806336--> END%% %%ANKI Cloze The {`%o`} format specifier outputs an {octal `unsigned int`}. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1707852083091--> END%% %%ANKI Basic Why doesn't the `%o` format specifier have a corresponding `%O` specifier? Back: There is no distinction between lower and uppercase octal digits. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1707852083096--> END%% %%ANKI Cloze The {`%s`} format specifiers outputs a {`NUL`-terminated string}. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1707852083100--> END%% %%ANKI Basic Which format specifier was probably used to yield `printf` output `abc`? Back: `%s` Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1707852083105--> END%% %%ANKI Cloze The {`%c`} format specifier outputs a {`char` character}. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1707852083109--> END%% %%ANKI Basic Which format specifier was probably used to yield `printf` output `a`? Back: `%c` Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1707852083113--> END%% %%ANKI Cloze The {`%p`} format specifier outputs a {`void*` address}. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1707852083117--> END%% %%ANKI Basic Which format specifier was probably used to yield `printf` output `0b80000000`? Back: `%p` Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1707852083121--> END%% %%ANKI Basic How is the address outputted by the `%p` format specifier written? Back: In an implementation-specific way. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1707852083126--> END%% %%ANKI Basic What should be done to a pointer outputted by the `%p` format specifier? Back: It should be cast to a `void*` pointer. Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020). <!--ID: 1732397726966--> END%% %%ANKI Basic Given `int64_t x`, why is `printf("%d", x)` a problem? Back: `%d` matches an `int` which is not necessarily 64-bits. Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016. <!--ID: 1708454462772--> END%% %%ANKI Basic What must you use when invoking `printf` with a fixed-width integer type? Back: `printf`-specific macros. Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016. <!--ID: 1708454462777--> END%% %%ANKI Basic What is `PRId32` an example macro for? Back: A macro that expands to the correct specifier for a 32-bit signed integral type. Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016. <!--ID: 1708454462780--> END%% %%ANKI Cloze {`PRId32`} is to signed whereas {`PRIu32`} is to unsigned. Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1708454462784--> END%% %%ANKI Basic Which C header specifies `printf` macros for fixed-width integral types? Back: `<inttypes.h>` Reference: “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962). <!--ID: 1708454462788--> END%% %%ANKI Basic Given `int32_t x`, how might we invoke `printf` on it? Back: `printf("%" PRId32, x)` Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016. <!--ID: 1708454584564--> END%% %%ANKI Basic What prefix do `printf` macros from `<inttypes.h>` share? Back: `PRI` Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016. <!--ID: 1708454584568--> END%% ## Bibliography * Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016. * Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020). * “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962).