| <html lang="en"> |
| <head> |
| <title>Hex Floats - Using the GNU Compiler Collection (GCC)</title> |
| <meta http-equiv="Content-Type" content="text/html"> |
| <meta name="description" content="Using the GNU Compiler Collection (GCC)"> |
| <meta name="generator" content="makeinfo 4.13"> |
| <link title="Top" rel="start" href="index.html#Top"> |
| <link rel="up" href="C-Extensions.html#C-Extensions" title="C Extensions"> |
| <link rel="prev" href="Decimal-Float.html#Decimal-Float" title="Decimal Float"> |
| <link rel="next" href="Fixed_002dPoint.html#Fixed_002dPoint" title="Fixed-Point"> |
| <link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> |
| <!-- |
| Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998, |
| 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, |
| 2008 Free Software Foundation, Inc. |
| |
| Permission is granted to copy, distribute and/or modify this document |
| under the terms of the GNU Free Documentation License, Version 1.2 or |
| any later version published by the Free Software Foundation; with the |
| Invariant Sections being ``Funding Free Software'', the Front-Cover |
| Texts being (a) (see below), and with the Back-Cover Texts being (b) |
| (see below). A copy of the license is included in the section entitled |
| ``GNU Free Documentation License''. |
| |
| (a) The FSF's Front-Cover Text is: |
| |
| A GNU Manual |
| |
| (b) The FSF's Back-Cover Text is: |
| |
| You have freedom to copy and modify this GNU Manual, like GNU |
| software. Copies published by the Free Software Foundation raise |
| funds for GNU development.--> |
| <meta http-equiv="Content-Style-Type" content="text/css"> |
| <style type="text/css"><!-- |
| pre.display { font-family:inherit } |
| pre.format { font-family:inherit } |
| pre.smalldisplay { font-family:inherit; font-size:smaller } |
| pre.smallformat { font-family:inherit; font-size:smaller } |
| pre.smallexample { font-size:smaller } |
| pre.smalllisp { font-size:smaller } |
| span.sc { font-variant:small-caps } |
| span.roman { font-family:serif; font-weight:normal; } |
| span.sansserif { font-family:sans-serif; font-weight:normal; } |
| --></style> |
| <link rel="stylesheet" type="text/css" href="../cs.css"> |
| </head> |
| <body> |
| <div class="node"> |
| <a name="Hex-Floats"></a> |
| <p> |
| Next: <a rel="next" accesskey="n" href="Fixed_002dPoint.html#Fixed_002dPoint">Fixed-Point</a>, |
| Previous: <a rel="previous" accesskey="p" href="Decimal-Float.html#Decimal-Float">Decimal Float</a>, |
| Up: <a rel="up" accesskey="u" href="C-Extensions.html#C-Extensions">C Extensions</a> |
| <hr> |
| </div> |
| |
| <h3 class="section">6.13 Hex Floats</h3> |
| |
| <p><a name="index-hex-floats-2246"></a> |
| ISO C99 supports floating-point numbers written not only in the usual |
| decimal notation, such as <code>1.55e1</code>, but also numbers such as |
| <code>0x1.fp3</code> written in hexadecimal format. As a GNU extension, GCC |
| supports this in C90 mode (except in some cases when strictly |
| conforming) and in C++. In that format the |
| ‘<samp><span class="samp">0x</span></samp>’ hex introducer and the ‘<samp><span class="samp">p</span></samp>’ or ‘<samp><span class="samp">P</span></samp>’ exponent field are |
| mandatory. The exponent is a decimal number that indicates the power of |
| 2 by which the significant part will be multiplied. Thus ‘<samp><span class="samp">0x1.f</span></samp>’ is |
| 1 15/16, |
| ‘<samp><span class="samp">p3</span></samp>’ multiplies it by 8, and the value of <code>0x1.fp3</code> |
| is the same as <code>1.55e1</code>. |
| |
| <p>Unlike for floating-point numbers in the decimal notation the exponent |
| is always required in the hexadecimal notation. Otherwise the compiler |
| would not be able to resolve the ambiguity of, e.g., <code>0x1.f</code>. This |
| could mean <code>1.0f</code> or <code>1.9375</code> since ‘<samp><span class="samp">f</span></samp>’ is also the |
| extension for floating-point constants of type <code>float</code>. |
| |
| </body></html> |
| |
