前面已经讲了C语言基础，从此以后将进行编程实战。C数据类型名较长，编程输入不太方便。

       下面编写一个定义数据类型别名的程序，并定义实现后面例程常用到的位操作及字符串操作函数。

        1. 打开前面教程中创建的C51 Template.uvproj。新建两个文件分别以mtype.h，mytype.c存于C51 Template文件夹下的Library文件夹中。

        2. 完成mtype.h

        2.1 输入如下宏语句，以避免重复包含时编译出错，并在文件开头添加包含文件信息的注释。

/*mytype.hDesigned by Bill LiuVersion 0.0 Modified last by Bill Liu on 10/31/2021
*/
#ifndef __MYTYPE_H_
#define __MYTYPE_H_#endif

     2.2 添加包含Keil C函数库并注释起来。当需用到时取消注释即可。

/*mytype.hDesigned by Bill LiuVersion 0.0 Modified last by Bill Liu on 10/31/2021
*/
#ifndef __MYTYPE_H_
#define __MYTYPE_H_#include <math.h>
//#include <stdlib.h>
//#include <stdio.h>
//#include <ctype.h>
//#include <string.h>
//#include <intrins.h>#endif

    2.3 定义数据类型别名，下面使用typedef定义别名。别名定义时，分别定义了大小写别名，这样可避免使用别名时，没注意到大小写时编译出错。如下：

/*mytype.hDesigned by Bill LiuVersion 0.0 Modified last by Bill Liu on 10/31/2021
*/
#ifndef __MTYPE_H_
#define __MTYPE_H_//#include <math.h>
//#include <stdlib.h>
//#include <stdio.h>
//#include <ctype.h>
//#include <string.h>
//#include <intrins.h>
#ifndef BYTE
typedef  unsigned char  BYTE;
#endif
#ifndef byte
typedef unsigned char byte;
#endif
#ifndef ui8
typedef  unsigned char ui8;
#endif
#ifndef UI8
typedef unsigned char UI8;
#endif
#ifndef U8
typedef unsigned char U8;
#endif
#ifndef u8
typedef  unsigned char u8;
#endif#ifndef uchar
typedef  unsigned char uchar;
#endif#ifndef INT8
typedef  signed char INT8;
#endif#ifndef int8
typedef  signed char int8;
#endif#ifndef I8
typedef signed char I8 ;
#endif#ifndef i8
typedef signed char i8;
#endif#ifndef WORD 
typedef unsigned int WORD;
#endif#ifndef word 
typedef  unsigned int word;
#endif#ifndef UINT 
typedef  unsigned int UINT;
#endif#ifndef uint 
typedef  unsigned int uint;
#endif#ifndef UI16 
typedef unsigned int  UI16;
#endif#ifndef ui16 
typedef  unsigned int ui16;
#endif#ifndef U16 
typedef  unsigned int U16;
#endif#ifndef  u16 
typedef   unsigned int u16;
#endif#ifndef  UINT16 
typedef unsigned int UINT16;
#endif#ifndef  uint16 
typedef   unsigned int uint16;
#endif#ifndef I16 
typedef  signed int I16;
#endif#ifndef i16 
typedef  signed int i16;
#endif#ifndef INT16 
typedef  signed int INT16;
#endif#ifndef int16 
typedef  signed int int16;
#endif#ifndef DWORD 
typedef unsigned long DWORD;
#endif#ifndef UINT32 
typedef unsigned long  UINT32;
#endif#ifndef uint32 
typedef  unsigned long uint32;
#endif#ifndef UI32 
typedef unsigned long UI32;
#endif#ifndef ui32 
typedef unsigned long ui32;
#endif#ifndef U32 
typedef unsigned long  u32;
#endif
#ifndef Ui32 
typedef unsigned long  Ui32;
#endif#ifndef I32 
typedef  long signed int I32;
#endif#ifndef i32 
typedef  signed long   i32;
#endif#ifndef INT32 
typedef  signed long INT32;
#endif#ifndef int32 
typedef  signed long int32;
#endif#ifndef FP32 
typedef   float FP32;
#endif#ifndef fp32 
typedef float fp32;
#endif#ifndef F32 
typedef   float F32;
#endif#ifndef Fp32 
typedef   float Fp32;
#endif#ifndef f32 
typedef   float f32;
#endif#ifndef F64 
typedef  double  F64;
#endif#ifndef f64 
typedef  double  f64; 
#endif#ifndef FP64 
typedef  double  FP64;
#endiftypedef enum
{FALSE = 0,TRUE  = 1}BOOL;#endif

    2.4 定义位操作函数。 单片机程序很大一部分是写寄存器，改变寄存器某位的值，但有的寄存器可以直接进行位读写,有的则不能.51单片机中寄存器地址可以被8整除的一般可以可以直接进行位读写，否则就不可以。不可以的，就需先将寄存器的值读入一个变量中，再改变变量对应需要改变的位，然后再将这个变量赋值给寄存器。如果每次都写这样的代码，就会比较费事。先写成库函数，到时直接调用就比较方便。

     2.4.1 在mtype.h定义位操作函数。在定义函数前,先声明一个枚举型,以限制bit位的位置的取值范围。

//function for operating data's bit  typedef enum   //define char bit position range
{pos0=0,     //define bit0 position as 0pos1,       //define bit1 position as 1pos2,       //define bit2 position as 2pos3,				//define bit3 position as 3pos4,       //define bit4 position as 4pos5,       //define bit5 position as 5pos6,				//define bit6 position as 6pos7 				//define bit6 position as 6
} BITPOS;/**********************************************************************
Function: SetBit(BYTE* pBYTE, BITPOS bPos); 
Return value: changed byte value
Discription: set one bit of 8bits data  as 1
Example:BYTE tem = T4T3M;  //define tem and read T4T3M register into temT4T3M = SetBit(&tem, pos0);
***********************************************************************/
BYTE SetBit(BYTE* pBYTE, BITPOS bPos);/**********************************************************************
Function: ResetBit(BYTE* pBYTE, BITPOS bPos);
Return value: changed byte value
Discription: reset one bit of 8bits data  as 0
Example:BYTE tem = T4T3M;  //define tem and read T4T3M register into temT4T3M = ResetBit(&tem, pos0);
***********************************************************************/
BYTE ResetBit(BYTE* pBYTE, BITPOS bPos);/**********************************************************************
Function: SetBits(BYTE* pBYTE,BITPOS hBit,BITPOS lBit,BYTE mData); 
Return value: changed byte value
Discription: change  continue bits of 8bits data  to mdata
Example:BYTE tem = T4T3M;  //define tem and read T4T3M register into temT4T3M = SetBits(&tem, 4, 2, 0x05);
***********************************************************************/
BYTE SetBits(BYTE* pBYTE,BITPOS hBit,BITPOS lBit,BYTE mData);   /**********************************************************************
Function: GetBit(i8 mData,BITPOS pos); 
Return value: specified bit value
Discription: Get specified bit of char data
Example:i8 tem = T4T3M;  //define tem and read T4T3M register into temui8 tem1;tem1 = GetBit(tem, 4);
***********************************************************************/
ui8 GetBit(i8 mData,BITPOS pos);   /**********************************************************************
Function: GetBits(i8 mData,BITPOS hBit,BITPOS lBit); 
Return value: specified bits value
Discription: Get specified continue bits of char data
Example:i8 tem = T4T3M;  //define tem and read T4T3M register into temui8 tem1;tem1 = GetBits(tem, 4, 2);
***********************************************************************/
ui8 GetBits(i8 mData,BITPOS hBit,BITPOS lBit);

   2.4.2 在mtype.c中实现定义函数。

//***********************************************************************/
BYTE SetBit(BYTE* pBYTE, BITPOS bPos)
{*pBYTE |= 1 << bPos;return  *pBYTE;
}
//End of SetBit(BYTE* pBYTE, BITPOS bPos)//***********************************************************************/
BYTE ResetBit(BYTE* pBYTE, BITPOS bPos)
{*pBYTE &= ~(1 << bPos);return  *pBYTE;
}
//End of ResetBit(BYTE* pBYTE, BITPOS bPos)//***********************************************************************/
BYTE SetBits(BYTE* pBYTE,BITPOS hBit,BITPOS lBit,BYTE mData)
{ui8 tem = hBit - lBit + 1;tem = (1 << tem) - 1;mData &= tem;              	//discard bits may be redundant*pBYTE &= ~(tem << lBit);  	//clear specified bits*pBYTE |= (mData << lBit);  //set specified bitsreturn  *pBYTE;
}
//End of SetBits(BYTE* pBYTE,BITPOS hBit,BITPOS lBit,BYTE mData)//***********************************************************************/
ui8 GetBit(i8 mData,BITPOS pos) 
{return (mData & (1 << pos)) >> pos;
}
//End of GetBit(i8 mData,BITPOS pos)//***********************************************************************/
ui8 GetBits(i8 mData,BITPOS hBit,BITPOS lBit)
{ui8 tem = hBit - lBit + 1;tem  = 1 << tem - 1;return    (mData & tem << lBit) >> lBit;
}
//End of GetBits(i8 mData,BITPOS hBit,BITPOS lBit)

         2.5 字符串相关的函数定义及实现。字符串是一个以0结尾的ASCII码数组。

         2.5.1 函数定义

 /string function
/***********************************************************************
Function: UcarBToString(ui8 src,ui8* desString);
Return value: desString
Discription: covert binary places of an unsigned char data binary places to string
Example:ui8 tem = 123;ui8 mstr[9] = {0};UcharBToString(tem,mstr);
***********************************************************************/
ui8* UcharBToString(ui8 src,ui8* desString);/***********************************************************************
Function: BStringToUchar(ui8 src[],ui8* destData);
Return value
Discription: covert string made of binary  character to unsigned char
Example:ui8 mstr[9] = "10101";ui8 tem;BStringToUchar(mstr,&tem);
***********************************************************************/
ui8 BStringToUchar(ui8 src[],ui8* destData);/***********************************************************************
Function: SubString(ui8* srcString,ui8* desString,ui8 startPos, ui8 size_n);
Return Value: desString(substring)
Discription:cut a string from destination string
Example:ui8 str1[10] = "123459789";ui8 mstr2[9] = {0};SubString(str1,mstr2,2,4); //"3456"
***********************************************************************/
ui8* SubString(ui8* srcString,ui8* desString, ui8 startPos, ui8 size_n);

       2.5.2 函数实现

//***********************************************************************/
ui8* UcharBToString(ui8 src,ui8* desString)
{ui8 i;memset(desString,0,strlen(desString));for(i = 0; i < 8; i++){if((src << i)&0x80)desString[i] = '1';elsedesString[i] = '0';}return desString;
}
//End of UcharBToString(ui8 src,ui8* desString)//***********************************************************************/
ui8 BStringToUchar(ui8 src[],ui8* destData)
{ui8 len = strlen(src);ui8 i;*destData = 0;for(i = len -1; i >= 0; i--){if(src[i])*destData += 1 << i;}return *destData;
}
//End of BStringToUchar(ui8 src[],ui8* destData)//***********************************************************************/
ui8* SubString(ui8* srcString,ui8* desString, ui8 startPos, ui8 size_n)
{ui8 i;memset(desString,0,strlen(desString));if(sizeof(srcString)/sizeof(char)> startPos + size_n){for(i = 0; i < size_n; i++)desString[i] =  srcString[startPos + i];}return desString;
}
//End of SubString(ui8* srcString,ui8* desString, ui8 startPos, ui8 size_n)