--- title: Strings TARGET DECK: Obsidian::STEM FILE TAGS: c17 tags: - c17 --- ## Overview A contiguous sequence of characters terminated by the `NUL` character (refer to [[ascii|ASCII]]). Text data is said to be more platform-independent than [[endianness|binary]] data since it is unaffected by word size or byte ordering. %%ANKI Basic What is a C-style string? Back: A character array terminated with a `NUL` character. Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016. END%% %%ANKI Basic What character terminates all C-style strings? Back: `NUL` Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016. END%% %%ANKI Basic What is the decimal value of `NUL` in ASCII encoding? Back: `0` Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016. END%% %%ANKI Basic Text is more platform-independent than e.g. integer encodings because it is unaffected by what two properties? Back: Word size and byte ordering. Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016. END%% %%ANKI Basic What kind of array can be expressed as a literal? Back: Strings. Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020). END%% %%ANKI Cloze A {string} is a {`NUL`}-terminated array of {`char`}. Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020). END%% %%ANKI Cloze `` uses prefix {`mem`} to refer to {array} arguments. Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020). END%% %%ANKI Cloze `` uses prefix {`str`} to refer to {string} arguments. Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020). END%% ## `printf` 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). Tags: printf END%% %%ANKI Basic Which header file contains basic `printf` functionality? 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). Tags: printf 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). Tags: printf 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). Tags: printf END%% | 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf END%% 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf END%% 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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. Tags: printf 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. Tags: printf 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. Tags: printf 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. Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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). Tags: printf 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. Tags: printf 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. Tags: printf 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. Tags: printf 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). Tags: printf END%% %%ANKI Basic Which C header specifies `printf` macros for fixed-width integral 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). Tags: printf 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. Tags: printf END%% %%ANKI Basic What prefix do `printf` macros from `` 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. Tags: printf END%% ## Escape Sequences C has a standard for processing different escape sequences. Many languages built with C in mind parse these escape sequences in a similar way. * `\ooo`: Consists of one to three octal digits. * [[bash/index|Bash]] supports this sequence as `$'\ooo'`. %%ANKI Basic How are C escape sequences for octal digits denoted? Back: As `\ooo`. Reference: Brian W. Kernighan and Dennis M. Ritchie, *The C Programming Language*, 2nd ed (Englewood Cliffs, N.J: Prentice Hall, 1988). END%% %%ANKI Basic In C, `\ooo` allows specifying how many octal digits? Back: One to three. Reference: Brian W. Kernighan and Dennis M. Ritchie, *The C Programming Language*, 2nd ed (Englewood Cliffs, N.J: Prentice Hall, 1988). END%% %%ANKI Basic How are C escape sequences exposed in bash? Back: Using ANSI-C quoting, i.e. `$$'string'`. Reference: Mendel Cooper, “Advanced Bash-Scripting Guide,” n.d., 916. Tags: bash END%% * `\xhh`: Consists of one or more [[radices#Hexadecimal|hexadecimal]] digits. The `x` prefix is required to distinguish from octal escape sequences. * [[bash/index|Bash]] supports this sequence as `$'\xhh'`. One or two digits is supported. %%ANKI Basic How are C escape sequences for hexadecimal digits denoted? Back: As `\xhh`. Reference: Brian W. Kernighan and Dennis M. Ritchie, *The C Programming Language*, 2nd ed (Englewood Cliffs, N.J: Prentice Hall, 1988). END%% %%ANKI Basic In C, `\x` allows specifying how many hexadecimal digits? Back: One or more. Reference: Brian W. Kernighan and Dennis M. Ritchie, *The C Programming Language*, 2nd ed (Englewood Cliffs, N.J: Prentice Hall, 1988). END%% %%ANKI Basic What footgun does C's `\x` sequence expose? Back: Using more than two hexadecimal digits can produce undefined results. Reference: Arnold D. Robbins, “GAWK: Effective AWK Programming,” October 2023, [https://www.gnu.org/software/gawk/manual/gawk.pdf](https://www.gnu.org/software/gawk/manual/gawk.pdf). END%% * `\uhhhh`: Introduced in C11 to represent Unicode code points. *Must* have exactly four hexadecimal characters specified with `0` leading padding if necessary. * [[bash/index|Bash]] supports this sequence as `$'uhhhh'`. One to four hex digits is supported. %%ANKI Basic What two ways are C escape sequences for unicode denoted? Back: As `\uhhhh` or `\Uhhhhhhhh`. Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020). Tags: encoding::unicode END%% %%ANKI Basic In C, `\u` allows specifying how many hexadecimal digits? Back: Exactly four. Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020). Tags: encoding::unicode END%% %%ANKI Basic In what standard were C's `\u` and `\U` escape sequences introduced? Back: C11. Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020). Tags: encoding::unicode END%% * `\Uhhhhhhhh`: Introduced in C11 to represent larger unicode code points. *Must* have exactly eight hexadecimal characters specified with `0` leading padding if necessary. %%ANKI Basic In C, `\U` allows specifying how many hexadecimal digits? Back: Exactly eight. Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020). Tags: encoding::unicode END%% %%ANKI Basic Why does C have both `\u` and `\U`? Back: `\U` accommodates for larger code point values. Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020). Tags: encoding::unicode END%% ## Bibliography * Arnold D. Robbins, “GAWK: Effective AWK Programming,” October 2023, [https://www.gnu.org/software/gawk/manual/gawk.pdf](https://www.gnu.org/software/gawk/manual/gawk.pdf). * Brian W. Kernighan and Dennis M. Ritchie, *The C Programming Language*, 2nd ed (Englewood Cliffs, N.J: Prentice Hall, 1988). * 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). * Mendel Cooper, “Advanced Bash-Scripting Guide,” n.d., 916. * “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).