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diff --git a/reference/C/FUNCTIONS/format.html b/reference/C/FUNCTIONS/format.html new file mode 100644 index 0000000..0d18e69 --- /dev/null +++ b/reference/C/FUNCTIONS/format.html @@ -0,0 +1,315 @@ +<title>printf format identifiers.</title> +<head> +<script language="JavaScript"> +</script> +</head> +<body bgcolor="#ffffcc"> +<hr> +<center> +<h1>printf format identifiers.</h1> +</center> +<hr> +<p> +printf formatting is controlled by 'format identifiers' which, are shown +below in their simplest form. +<p> +<center> +<table border bgcolor="ivory" width="80%"> +<tr> +<td> +<pre> + + %d %i Decimal signed integer. + %o Octal integer. + %x %X Hex integer. + %u Unsigned integer. + %c Character. + %s String. See below. + %f double + %e %E double. + %g %G double. + %p pointer. + %n Number of characters written by this printf. + No argument expected. + %% %. No argument expected. + +</pre> +</td> +<tr> +</table> +</center> +<p> + +These identifiers actually have upto 6 parts as shown in the table below. +They MUST be used in the order shown. +<p> + +<center> +<table border bgcolor="ivory" width="80%"> +<tr align=center> +<td><a href="#percent">%</a></td> +<td><a href="#flags">Flags</a></td> +<td><a href="#width">Minimum field width</a></td> +<td><a href="#period">Period</a></td> +<td><a href="#precision">Precision. Maximum field width</a></td> +<td><a href="#id">Argument type</a></td> +</tr> +<tr align=center> +<td>Required</td> +<td>Optional</td> +<td>Optional</td> +<td>Optional</td> +<td>Optional</td> +<td>Required</td> +</table> +</center> +<p> + +<a name=percent> +<hr> +<h2>%</h2> +The % marks the start and therfore is manatory. +<p> + +<a name=flags> +<hr> +<h2>Flags</h2> +The format identifers can be altered from their default function by +applying the following <b>flags</b>: +<p> + +<center> +<table border bgcolor="ivory" width="80%"> +<tr> +<td> +<pre> + + - Left justify. + 0 Field is padded with 0's instead of blanks. + + Sign of number always O/P. + blank Positive values begin with a blank. + # Various uses: + %#o (Octal) 0 prefix inserted. + %#x (Hex) 0x prefix added to non-zero values. + %#X (Hex) 0X prefix added to non-zero values. + %#e Always show the decimal point. + %#E Always show the decimal point. + %#f Always show the decimal point. + %#g Always show the decimal point trailing + zeros not removed. + %#G Always show the decimal point trailing + zeros not removed. + +</pre> +</td> +</tr> +</table> +</center> + +<ul> +<li>The flags must follow the <a href="#percent">%</a>. +<li>Where it makes sense, more than one flag can be used. +</ul> +Here are a few more examples. +<p> + +<center> +<table border bgcolor="ivory" width="80%"> +<tr> +<td> +<pre> + + printf(" %-10d \n", number); + printf(" %010d \n", number); + printf(" %-#10x \n", number); + printf(" %#x \n", number); +</pre> +</td> +</tr> +</table> +</center> + +<p> +<a name=width> +<hr> +<h2>Minimum field width.</h2> +By default the width of a field will be the minimum required to hold +the data. If you want to increase the field width you can use the +following syntax. +<p> +<center> +<table border bgcolor="ivory" width="80%"> +<tr> +<td> +<pre> + + main() + { + int number = 5; + char *pointer = "little"; + + printf("Here is a number-%4d-and a-%10s-word.\n", number, pointer); + } + + /********************************* + * + * Program result is: + * + * Here is a number- 5-and a- little-word. + * + *********************************/ +</pre> +</td> +</tr> +</table> +</center> +<p> +As you can see, the data is right justified within the field. It can +be left justified by using the <a href="#flags">- flag</a>. +A <a href="#precision">maximum string</a> width can also be specified. +<p> +The width can also be given as a variable as shown below. +<p> +<center> +<table border bgcolor="ivory" width="80%"> +<tr> +<td> +<pre> + + main() + { + int number=5; + + printf("---%*d----\n", 6, number); + } + + /********************************* + * + * Program result is: + * + * ---- 5--- + * + *********************************/ +</pre> +</td> +</tr> +</table> +</center> +<p> +The * is replaced with the supplied <b>int</b> to provide the ability to +dynamically specify the field width. +<p> +<hr> +<a name=period> +<h2>Period</h2> +If you wish to specify the <a href="#precision">precision</a> of an argument, +it MUST be prefixed with the period. +<p> +<a name=precision> +<hr> +<h2>Precision</h2> + +The Precision takes different meanings for the different format types. + +<h3>Float Precision</h3> +<pre> + %8.2f +</pre> +This says you require a total field of 8 characters, within the 8 +characters the last 2 will hold the decimal part. + +<pre> + %.2f +</pre> + +The example above requests the minimum field width and the last two +characters are to hold the decimal part. + +<h3>Character String Maximum field width</h3> + +The precision within a string format specifies the maximum +field width. +<pre> + %4.8s +</pre> +Specifies a minimum width of 4 and a maximum width +of 8 characters. If the string is greater than 8 characters, +it will be cropped down to size. +<p> +<img src=../../GRAPHICS/computer.gif> +<a href=../EXAMPLES/sprintf1.c>Here is a little program</a> +that shows an alternative to <a href=strncpy.html>strncpy</a>. + +<h3>* Precision</h3> + +As with the 'width' above, the precision does not have to be hard +coded, the * symbol can be used and an integer supplied to give its +value. +<p> +<hr> +<a name=id> +<h2>Format Identifiers</h2> +The format identifier describes the expected data. The identifier is the +character that ends +Here is a list of the format identifers as used in 'printf' ,'sprintf' +,'fprintf' and 'scanf'. + +<ol> +<li>Except for '%' and 'n', all the identifiers expect to extract an argument +from the <b>printf</b> parameter list. +<li>All of the parmameters should be the value +to be inserted. EXCEPT %s, this expects a <a href="../CONCEPT/pointers.html"> +pointer</a> to be passed. +</ol> +<h2>An example.</h2> +<p> +<center> +<table border bgcolor="ivory" width="80%"> +<tr> +<td> +<pre> + + main() + { + int number=5; + char *pointer="little"; + + printf("Here is a number %d and a %s word.\n", number, pointer); + } + /********************************* + * + * Program result is: + * + * Here is a number 5 and a little word. + * + *********************************/ +</pre> +</td> +</tr> +</table> +</center> +<p> + +<hr> +<p> +<center> +<table border=2 width="80%" bgcolor="ivory"> +<tr align=center> +<td width="25%"> +<a href="../cref.html"> Top</a> +</td><td width="25%"> +<a href="../master_index.html"> Master Index</a> +</td><td width="25%"> +<a href="../SYNTAX/keywords.html"> Keywords</a> +</td><td width="25%"> +<a href="funcref.htm"> Functions</a> +</td> +</tr> +</table> +</center> +<p> +<hr> +<address>Martin Leslie +</address><p> +</body> +</html> |