#define PI 3.1415926
#define MAX_SIZE 100
#define GREETING "Hello, World!"

#define SQUARE(x) ((x) * (x))
#define MIN(a, b) ((a) < (b) ? (a) : (b))
#define POW(x, y) (pow(x, y))  // 假設(shè)pow是計(jì)算冪的函數(shù)

#include <stdio.h>
#include <stdlib.h>

#include <stdio.h>

int main() {
    printf("Hello, World!\n");
    return 0;
}

#include <stdlib.h>

int main() {
    int num = atoi("123");  // 將字符串轉(zhuǎn)換為整數(shù)
    return 0;
}

#include <string.h>

int main() {
    char str[100];
    strcpy(str, "Hello, World!");
    return 0;
}

#include "myheader.h"

// mathutils.h
int add(int a, int b);
int subtract(int a, int b);

#include "mathutils.h"

int main() {
    int sum = add(5, 3);
    int difference = subtract(5, 3);
    return 0;
}

// mydefs.h
#ifndef MYDEFS_H
#define MYDEFS_H

#define MAX_SIZE 100
#define URL "http://mywebsite.com"
#define PI 3.14159
#define SQUARE(x) ((x) * (x))
#define MIN(a, b) ((a) < (b) ? (a) : (b))
#define MAX(a, b) ((a) > (b) ? (a) : (b))

#endif // MYDEFS_H

#include <stdio.h>
#include "mydefs.h"

int main() {
    int size = MAX_SIZE;
    float radius = 4.5;
    float area = PI * SQUARE(radius);
    int minVal = MIN(10, 20);
    int maxVal = MAX(10, 20);

    printf("Max size: %d\n", size);
    printf("URL: %s\n", URL);
    printf("Area of circle: %.2f\n", area);
    printf("Minimum value: %d\n", minVal);
    printf("Maximum value: %d\n", maxVal);

    return 0;
}

#define DEBUG 1

#if DEBUG
    printf("Debug information\n");
#endif

#if defined(WIN32)
    printf("Windows platform\n");
#elif defined(LINUX)
    printf("Linux platform\n");
#else
    printf("Other platform\n");
#endif
// 如果 DEBUG 被定義且為1，則會打印調(diào)試信息。
// 接著檢查是否定義了 WIN32 或 LINUX，并根據(jù)定義打印相應(yīng)的平臺信息。

#define WINDOWS

#ifdef WINDOWS
    printf("Compiled for Windows\n");
#endif

#ifndef LINUX
    printf("Not compiled for Linux\n");
#endif
// 如果 WINDOWS 被定義，則會編譯相關(guān)的代碼。
// 如果 LINUX 沒有被定義，則編譯第二個(gè) printf。

// 假設(shè)這些宏是根據(jù)編譯環(huán)境預(yù)先定義的
#define WINDOWS
// #define LINUX
// #define MACOS

int main() {
    #ifdef WINDOWS
        printf("Running on Windows.\n");
    #elif defined(LINUX)
        printf("Running on Linux.\n");
    #elif defined(MACOS)
        printf("Running on MacOS.\n");
    #else
        printf("Unknown operating system.\n");
    #endif

    return 0;
}

// 將此注釋或取消注釋以啟用/禁用調(diào)試模式
#define DEBUG_MODE

int main() {
    #ifdef DEBUG_MODE
        printf("Debug mode is enabled.\n");
        // 調(diào)試相關(guān)的代碼
    #else
        printf("Debug mode is disabled.\n");
        // 非調(diào)試相關(guān)的代碼
    #endif

    return 0;
}

#define FEATURE_X
// #define FEATURE_Y

int main() {
    printf("Program starts.\n");

    #ifdef FEATURE_X
        printf("Feature X is enabled.\n");
        // 執(zhí)行與 Feature X 相關(guān)的代碼
    #endif

    #ifdef FEATURE_Y
        printf("Feature Y is enabled.\n");
        // 執(zhí)行與 Feature Y 相關(guān)的代碼
    #endif

    printf("Program ends.\n");
    return 0;
}

#line number "filename"

#pragma warning(disable : 4996) // 禁用特定的警告

#pragma optimize("", off) // 關(guān)閉優(yōu)化
// ...
#pragma optimize("", on) // 開啟優(yōu)化

#pragma region MyRegion
// ...
#pragma endregion MyRegion

#pragma pack(push, 1) // 設(shè)定1字節(jié)對齊
struct MyStruct {
    char a;
    int b;
};
#pragma pack(pop) // 恢復(fù)默認(rèn)對齊

#include <stdio.h>

int main() {
	printf("File :%s\n", __FILE__);
	printf("Date :%s\n", __DATE__);
	printf("Time :%s\n", __TIME__);
	printf("Line :%d\n", __LINE__);
#ifdef __cplusplus
	printf("Compiled in C++\n");
#else
	printf("Compiled in C\n");
#endif

	getchar();
	return 0;
}