Discussions today on the TUHS list about the signed/unsigned nature of the C char type led me to reexamine logs of my feature test package at http://www.math.utah.edu/pub/features/ I had 170 build logs for it from 2017.11.07, so I moved those aside and ran another set of builds in our current enlarged test farm. That generated another 361 fresh builds. Those tests are all with the C compiler named "cc". I did not explore what other C compilers did, but I strongly suspect that they all agree on any single platform. On all but THREE systems, the tests report that "char" is signed, with CHAR_MAX == +127. The three outliers have char unsigned with CHAR_MAX == +255, and are * ARM armv7l Linux 4.13.1 (2017) and 5.6.7 (2020) * SGI O2 R10000-SC (150 MHz) IRIX 6.5 (2017 and 2020) * IBM POWER8 CentOS Linux release 7.4.1708 (AltArch) (2017) So, while the ISO C Standards, and historical practice, leave it implementation dependent whether char is signed or unsigned, there is a strong majority for a signed type. ------------------------------------------------------------------------------- - Nelson H. F. Beebe Tel: +1 801 581 5254 - - University of Utah FAX: +1 801 581 4148 - - Department of Mathematics, 110 LCB Internet e-mail: beebe(a)math.utah.edu - - 155 S 1400 E RM 233 beebe(a)acm.org beebe(a)computer.org - - Salt Lake City, UT 84112-0090, USA URL: http://www.math.utah.edu/~beebe/ - -------------------------------------------------------------------------------