The first problem is that an int can be 1,2 or 4 bytes in size and it depends on the compiler, processor and OS. In this post I'll show how to use precisely defined types that you can use throughout your code so that you will not need to worry about the size of types.
Common types that you will use are signed and unsigned ints, so these will need to be defined and standardized:
Signed ints: sint8, sint16,sint32, sint64
Unsigned ints: uint8, uint16, uint32, uint64
For floating point I use, float32 and float64
The C language is missing the bool type, so I define this as well, which is great as I can now mix the embedded C code with the C++ unit test harness code running on my Windows PC. I also prefer returning a bool instead of error codes so as to keep things simple.
Here is an example of my defines.h that I use when writing C projects for PIC micro-controllers.
#ifndef DEFINES_H #define DEFINES_H #ifdef WIN32 typedef char sint8; // -128 T0 127 typedef unsigned char uint8; // 0 TO 255 typedef signed short sint16; // -32768 TO 32767 typedef unsigned short uint16; // 0 TO 65535 typedef long sint32; // -2147483648 TO 2147483647 typedef unsigned long uint32; //0 TO 4294967295 typedef float float32; //(1.4012984643248171e-45f) to(3.4028234663852886e+38f) typedef double double64; // 4.9406564584124655e-324 to 1.7976931348623158e+308 //A byte is a one byte unsigned integer typedef unsigned char BYTE; //A double word is a four byte unsigned integer typedef unsigned long DWORD; //A word is a two byte unsigned integer typedef unsigned short WORD; #else typedef signed int sint8; // -128 T0 127 typedef unsigned int uint8; // 0 TO 255 typedef signed long sint16; // -C32768 TO 32767 typedef unsigned long uint16; // 0 TO 65535 typedef signed long long sint32; // -2147483648 TO 2147483647 typedef unsigned long long uint32; //0 TO 4294967295 typedef float float32; //(1.4012984643248171e-45f) to(3.4028234663852886e+38f) //A byte is a one byte unsigned integer - already defined in CCS compiler //typedef unsigned int BYTE; //A word is a two byte unsigned integer typedef unsigned long WORD; //A double word is a four byte unsigned integer typedef unsigned long long DWORD; typedef unsigned char bool; #define true (bool)1 #define false (bool)0 #endif //C definition of null is (void *) 0, for C++ it is just 0 #ifndef NULL #ifdef __cplusplus #define NULL 0 #else #define NULL ((void *) 0) #endif #endif //Include guard #endif
In my future embedded C posts that I'll be using these types, eg sint16, in my example code.