User manual

MPLAB
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XC8 C Compiler User’s Guide
DS52053A-page 20  2012 Microchip Technology Inc.
2.4.7 Plain char Types
The type of a plain char is unsigned char. It is generally recommended that all def-
initions for the char type explicitly state the signedness of the object.
2.4.7.1 EXAMPLE
The following example
char foobar;
defines an unsigned char object called foobar.
2.4.7.2 DIFFERENCES
The 8-bit compilers have always treated plain char as an unsigned type.
The 16- and 32-bit compilers used signed char as the default plain char type. The
-funsigned-char option on those compilers changed the default type to be
unsigned char.
2.4.7.3 MIGRATION TO THE CCI
Any definition of an object defined as a plain char and using the 16- or 32-bit compilers
needs review. Any plain char that was intended to be a signed quantity should be
replaced with an explicit definition, for example.
signed char foobar;
You may use the -funsigned-char option on XC16/32 to change the type of plain
char, but since this option is not supported on XC8, the code is not strictly conforming.
2.4.8 Signed Integer Representation
The value of a signed integer is determined by taking the two’s complement of the inte-
ger.
2.4.8.1 EXAMPLE
The following shows a variable, test, that is assigned the value -28 decimal.
signed char test = 0xE4;
2.4.8.2 DIFFERENCES
All compilers have represented signed integers in the way described in this section.
2.4.8.3 MIGRATION TO THE CCI
No action required.