初学STM32编程时，经常见到数据类型定义的符号：u8、u16等，51都是自己定义数据类型的简写符号，STM32是哪里定义的呢？今天没事就看了看系统头文件，数据类型的定义在其中的3个头文件里：
（1）stdint.h（摘取定义部分）
代码语言：javascript复制/*
* 'signed' is redundant below, except for 'signed char' and if
* the typedef is used to declare a bitfield.
*/
/* 7.18.1.1 */
/* exact-width signed integer types */
typedef signed char int8_t;
typedef signed short int int16_t;
typedef signed int int32_t;
typedef signed __INT64 int64_t;
/* exact-width unsigned integer types */
typedef unsigned char uint8_t;
typedef unsigned short int uint16_t;
typedef unsigned int uint32_t;
typedef unsigned __INT64 uint64_t;
/* 7.18.1.2 */
/* smallest type of at least n bits */
/* minimum-width signed integer types */
typedef signed char int_least8_t;
typedef signed short int int_least16_t;
typedef signed int int_least32_t;
typedef signed __INT64 int_least64_t;
/* minimum-width unsigned integer types */
typedef unsigned char uint_least8_t;
typedef unsigned short int uint_least16_t;
typedef unsigned int uint_least32_t;
typedef unsigned __INT64 uint_least64_t;
/* 7.18.1.3 */
/* fastest minimum-width signed integer types */
typedef signed int int_fast8_t;
typedef signed int int_fast16_t;
typedef signed int int_fast32_t;
typedef signed __INT64 int_fast64_t;
/* fastest minimum-width unsigned integer types */
typedef unsigned int uint_fast8_t;
typedef unsigned int uint_fast16_t;
typedef unsigned int uint_fast32_t;
typedef unsigned __INT64 uint_fast64_t;
/* 7.18.1.4 integer types capable of holding object pointers */
#if __sizeof_ptr == 8
typedef signed __INT64 intptr_t;
typedef unsigned __INT64 uintptr_t;
#else
typedef signed int intptr_t;
typedef unsigned int uintptr_t;
#endif
/* 7.18.1.5 greatest-width integer types */
typedef signed __LONGLONG intmax_t;
typedef unsigned __LONGLONG uintmax_t;（2）STM32F10x.h（摘取定义部分）
代码语言：javascript复制/*!< STM32F10x Standard Peripheral Library old types (maintained for legacy purpose) */
typedef int32_t s32;
typedef int16_t s16;
typedef int8_t s8;
typedef const int32_t sc32; /*!< Read Only */
typedef const int16_t sc16; /*!< Read Only */
typedef const int8_t sc8; /*!< Read Only */
typedef __IO int32_t vs32;
typedef __IO int16_t vs16;
typedef __IO int8_t vs8;
typedef __I int32_t vsc32; /*!< Read Only */
typedef __I int16_t vsc16; /*!< Read Only */
typedef __I int8_t vsc8; /*!< Read Only */
typedef uint32_t u32;
typedef uint16_t u16;
typedef uint8_t u8;
typedef const uint32_t uc32; /*!< Read Only */
typedef const uint16_t uc16; /*!< Read Only */
typedef const uint8_t uc8; /*!< Read Only */
typedef __IO uint32_t vu32;
typedef __IO uint16_t vu16;
typedef __IO uint8_t vu8;
typedef __I uint32_t vuc32; /*!< Read Only */
typedef __I uint16_t vuc16; /*!< Read Only */
typedef __I uint8_t vuc8; /*!< Read Only */（3）core_cm3.h（摘取部分）
代码语言：javascript复制/**
* IO definitions
*
* define access restrictions to peripheral registers
*/
#ifdef __cplusplus
#define __I volatile /*!< defines 'read only' permissions */
#else
#define __I volatile const /*!< defines 'read only' permissions */
#endif
#define __O volatile /*!< defines 'write only' permissions */
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