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‎Test Environments

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== Test Environments ==

{| class="smalldiv"
| style="background-color:#F6F9ED" |
| style="background-color:#F6F9ED" | Hardware Comments
| style="background-color:#F6F9ED" | '''Nut/OS 4.6.4'''
| style="background-color:#F6F9ED" | '''Nut/OS 4.7.4'''
| style="background-color:#F6F9ED" | '''Nut/OS 4.8.0'''
| style="background-color:#F6F9ED" | '''Nut/OS 4.8.7'''
|-
| Ethernut 1.3 H
|
| No output of Double [http://ethernut.de/arc/WIKI_BINARIES_ZIPPED/output-format-enut13H-nutos-4.6.4.zip '''Binaries''']
| No output of Double [http://ethernut.de/arc/WIKI_BINARIES_ZIPPED/output-format-enut13H-nutos-4.7.4.zip '''Binaries''']
| No output of Double [http://ethernut.de/arc/WIKI_BINARIES_ZIPPED/output-format-enut13H-nutos-4.8.0.zip '''Binaries''']
| No output of Double [[Media:Output-format-enut13H-nutos-4.8.7.zip|'''Binaries''']] '''Compiler:''' AVR-GCC 4.3.2
|-
| Ethernut 2.1 B
|
| No output of Double [http://ethernut.de/arc/WIKI_BINARIES_ZIPPED/output-format-enut21B-nutos-4.6.4.zip '''Binaries''']
| No output of Double [http://ethernut.de/arc/WIKI_BINARIES_ZIPPED/output-format-enut21B-nutos-4.7.4.zip '''Binaries''']
| No output of Double [http://ethernut.de/arc/WIKI_BINARIES_ZIPPED/output-format-enut21B-nutos-4.8.0.zip '''Binaries''']
| No output of Double [[Media:Output-format-enut21B-nutos-4.8.7.zip|'''Binaries''']] '''Compiler:''' AVR-GCC 4.3.2
|-
| Ethernut 3.0 E
|
| OK [http://ethernut.de/arc/WIKI_BINARIES_ZIPPED/output-format-enut30E-nutos-4.6.4.zip '''Binaries''']
| NO
| OK [http://ethernut.de/arc/WIKI_BINARIES_ZIPPED/output-format-enut30E-nutos-4.8.0.zip '''Binaries''']
|
|-
| EIR 1.0 C
| Set jumper JP1 to DEBUG mode.
| OK [http://ethernut.de/arc/WIKI_BINARIES_ZIPPED/output-format-EIR1C-nutos-4.6.4.zip '''Binaries''']
| NO
| OK [http://ethernut.de/arc/WIKI_BINARIES_ZIPPED/output-format-EIR1C-nutos-4.8.0.zip '''Binaries''']
|
|-
| id="compilertd" colspan="5" |'''Compiler:''' ARM-GCC 4.2.2 ; AVR-GCC 4.3.0
|
|}

== Description ==

[[Image:Floatactivation.png|right|thumb|Nut/OS Configurator]]
On this page you will learn about the different format specifiers of the <code>printf()</code> function.

Note that you have to activate floating point numbers in the Nut/OS configurator in order to use them.

== Format Specifiers ==
{| class="contenttable"
!Format Specifier
!Data type
!Example
|-
|<source lang="c">%d</source>
|Int (Integer)
|161
|-
|<source lang="c">%c</source>
|Character
|a
|-
|<source lang="c">%f</source>
|Floating-point number (Holds a total of '''7''' digits)
|3.141592
|-
|<source lang="c">%lf</source>
|Double (long floating) (Holds a total of '''16''' digits)
|3.141592653589793
|-
|<source lang="c">%s</source>
|String
|abcdef
|-
|<source lang="c">%x</source>
|Hexadecimal
|A1
|}

== Source Code ==

<source lang="c">
#include <dev/board.h>
#include <stdio.h>

int main(void)
{
unsigned long baud = 115200;

NutRegisterDevice(&DEV_DEBUG, 0, 0);

freopen(DEV_DEBUG_NAME, "w", stdout);
_ioctl(_fileno(stdout), UART_SETSPEED, &baud);

unsigned int integf = 161;
float floatf = 3.141592;
double doublef = 3.141592653589793;
char characf = 'a';
char *stringf = "abcdef";

printf("Integer:\n\n");
printf("%d|\t\t\t(format specifier: %%d)\n", integf);
printf("%9d|\t\t(format specifier: %%9d)\n", integf);
printf("%09d|\t\t(format specifier: %%09d)\n", integf);
printf("%-9d|\t\t(format specifier: %%-9d)\n", integf);
printf("----------------------------------------------------\n");
printf("Floating:\n\n");
printf("%f|\t\t(format specifier: %%f)\n", (double)floatf);
printf("%1.2f|\t\t\t(format specifier: %%1.2f)\n", (double)floatf);
printf("%1.6f|\t\t(format specifier: %%1.6f)\n", (double)floatf);
printf("%1.8f|\t\t(format specifier: %%1.8f)\n", (double)floatf);
printf("%8.1f|\t\t(format specifier: %%8.1f)\n", (double)floatf);
printf("%8.3f|\t\t(format specifier: %%8.3f)\n", (double)floatf);
printf("%-8.3f|\t\t(format specifier: %%-8.3f)\n", (double)floatf);
printf("%08.3f|\t\t(format specifier: %%08.3f)\n", (double)floatf);
printf("----------------------------------------------------\n");
printf("Double: (long Floating)\n\n");
printf("%lf|\t\t(format specifier: %%lf)\n", doublef);
printf("%1.2lf|\t\t\t(format specifier: %%1.2lf)\n", doublef);
printf("%1.6lf|\t\t(format specifier: %%1.6lf)\n", doublef);
printf("%1.15lf|\t(format specifier: %%1.15lf)\n", doublef);
printf("%15.1lf|\t(format specifier: %%15.1lf)\n", doublef);
printf("%15.3lf|\t(format specifier: %%15.3lf)\n", doublef);
printf("%-15.3lf|\t(format specifier: %%-15.3lf)\n", doublef);
printf("%015.3lf|\t(format specifier: %%015.3lf)\n", doublef);
printf("----------------------------------------------------\n");
printf("Character:\n\n");
printf("%c|\t\t\t(format specifier: %%c)\n", characf);
printf("----------------------------------------------------\n");
printf("String:\n\n");
printf("%s|\t\t\t(format specifier: %%s)\n", stringf);
printf("----------------------------------------------------\n");
printf("Hexadecimal:\n\n");
printf("%d|\t\t\t(format specifier: %%d)\n", integf);
printf("%x|\t\t\t(format specifier: %%x)\n", integf);
printf("%X|\t\t\t(format specifier: %%X)\n", integf);

for(;;);

return 0;
}

</source>

== Details ==

<source lang="c">
unsigned int integf = 161;
float floatf = 3.141592;
double doublef = 3.141592653589793;
char characf = 'a';
char *stringf = "abcdef";
</source>
At first we declare a number of variables and a pointer which will later be formatted and displayed by the format specifiers within <code>printf</code> statements.

<source lang="c">
printf("Integer:\n\n");
printf("%d (format specifier: %%d)\n", integf);
printf("%9d (format specifier: %%9d)\n", integf);
printf("%09d (format specifier: %%09d)\n", integf);
printf("%-9d (format specifier: %%-9d)\n", integf);
</source>
As you can see in the output section, <code>%d</code> displayes an integer value without any spaces in front of.
This specifier can be modified by entering numbers between the <code>%</code> and the <code>d</code>
By using <code>%9d</code> the integer value takes at least 9 spaces for itself. If the value has less than 9 digits, the spaces getfilled by blanks.
If you use <code>%09d</code> instead the spaces gets filled by zeros.

This is called ''Minimum Field Width.''

Putting a - (Minus) in front of the Minimum Field Width value causes the output to be justified on the left.

<source lang="c">
printf("Floating:\n\n");
printf("%f|\t\t(format specifier: %%f)\n", (double)floatf);
printf("%1.2f|\t\t\t(format specifier: %%1.2f)\n", (double)floatf);
printf("%1.6f|\t\t(format specifier: %%1.6f)\n", (double)floatf);
printf("%1.8f|\t\t(format specifier: %%1.8f)\n", (double)floatf);
printf("%8.1f|\t\t(format specifier: %%8.1f)\n", (double)floatf);
printf("%8.3f|\t\t(format specifier: %%8.3f)\n", (double)floatf);
printf("%-8.3f|\t\t(format specifier: %%-8.3f)\n", (double)floatf);
printf("%08.3f|\t\t(format specifier: %%08.3f)\n", (double)floatf);
</source>
The specifier for floating point numbers <code>%f</code> may be customized as well.

<code>%1.6f</code> for example sets the ''Minimum Field Width'' to 1 and the ''Precision Specifier'' to 6. This is the number of decimal places.
Note that the statements using <code>%f</code> and <code>%1.6f</code> look the same. Thats because <code>%f</code> uses a default decimal places (Precision) value of 6, as <code>%1.6f</code> does.
When using more than 7 digits, e.g. %1.7f (1+7=8), as only 7 digits are supported, the additional ones hold random numbers. (See line 5)

<source lang="c">
printf("Double: (long Floating)\n\n");
printf("%lf|\t\t(format specifier: %%lf)\n", doublef);
printf("%1.2lf|\t\t\t(format specifier: %%1.2lf)\n", doublef);
printf("%1.6lf|\t\t(format specifier: %%1.6lf)\n", doublef);
printf("%1.15lf|\t(format specifier: %%1.15lf)\n", doublef);
printf("%15.1lf|\t(format specifier: %%15.1lf)\n", doublef);
printf("%15.3lf|\t(format specifier: %%15.3lf)\n", doublef);
printf("%-15.3lf|\t(format specifier: %%-15.3lf)\n", doublef);
printf("%015.3lf|\t(format specifier: %%015.3lf)\n", doublef);
</source>
<source lang="c">
printf("Character:\n\n");
printf("%c|\t\t\t(format specifier: %%c)\n", characf);
</source>
<source lang="c">
printf("%s|\t\t\t(format specifier: %%s)\n", stringf);
</source>
<source lang="c">
printf("Hexadecimal:\n\n");
printf("%d|\t\t\t(format specifier: %%d)\n", integf);
printf("%x|\t\t\t(format specifier: %%x)\n", integf);
printf("%X|\t\t\t(format specifier: %%X)\n", integf);
</source>
Note that the last two <code>printf</code> statements use the same <code>int</code> variable as the first one does. By using the <code>%x</code> specifier, the decimal number gets automatically converted into the hexadecimal system.

== Output ==
Output with Nut/OS 4.6.4 on Ethernut 3.0 E:
Integer:

161| (format specifier: %d)
161| (format specifier: %9d)
000000161| (format specifier: %09d)
161 | (format specifier: %-9d)
----------------------------------------------------
Floating:

3.141592| (format specifier: %f)
3.14| (format specifier: %1.2f)
3.141592| (format specifier: %1.6f)
3.14159203| (format specifier: %1.8f)
3.1| (format specifier: %8.1f)
3.142| (format specifier: %8.3f)
3.142 | (format specifier: %-8.3f)
0003.142| (format specifier: %08.3f)
----------------------------------------------------
Double: (long Floating)

3.141593| (format specifier: %lf)
3.14| (format specifier: %1.2lf)
3.141593| (format specifier: %1.6lf)
3.141592653589793| (format specifier: %1.15lf)
3.1| (format specifier: %15.1lf)
3.142| (format specifier: %15.3lf)
3.142 | (format specifier: %-15.3lf)
00000000003.142| (format specifier: %015.3lf)
----------------------------------------------------
Character:

a| (format specifier: %c)
----------------------------------------------------
String:

abcdef| (format specifier: %s)
----------------------------------------------------
Hexadecimal:

161| (format specifier: %d)
a1| (format specifier: %x)
A1| (format specifier: %X)

== See also ==
* More [[Nut/OS Examples]]

== External Links ==

[http://en.wikipedia.org/wiki/Printf#1970s:_C.2C_Lisp] Wikipedia article about the printf function".

 

[[Category:Code Snippets]]

{{Languages}}

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