使用C語言可以編寫各種各樣的小軟件,以下是一些常見的類型：

控制臺應用程序

1. 簡單計算器
   • 功能：實現基本的加、減、乘、除、取余運算，用戶輸入算式,程序輸出結果。
   • 示例代碼：

     #include <stdio.h>

int main() { double num1, num2; char op; printf("請輸入算式（如 3 + 5）："); scanf("%lf %c %lf", &num1, &op, &num2);

switch (op) {
    case '+':
        printf("結果是：%.2lf\n", num1 + num2);
        break;
    case '-':
        printf("結果是：%.2lf\n", num1 - num2);
        break;
    case '*':
        printf("結果是：%.2lf\n", num1 * num2);
        break;
    case '/':
        if (num2 != 0) {
            printf("結果是：%.2lf\n", num1 / num2);
        } else {
            printf("除數不能為0\n");
        }
        break;
    case '%':
        if (num2 != 0) {
            printf("結果是：%.0lf\n", (int)num1 % (int)num2);
        } else {
            printf("除數不能為0\n");
        }
        break;
    default:
        printf("無效的運算符\n");
}
return 0;

**文件統計工具**
   - 功能：統計一個文本文件中字符數、單詞數和行數。
   - 示例代碼：
```c
#include <stdio.h>
#include <ctype.h>
int main() {
    FILE *file = fopen("example.txt", "r");
    if (file == NULL) {
        perror("無法打開文件");
        return 1;
    }
    int charCount = 0, wordCount = 0, lineCount = 0;
    int inWord = 0;
    int c;
    while ((c = fgetc(file)) != EOF) {
        charCount++;
        if (isspace(c)) {
            inWord = 0;
        } else if (!inWord) {
            inWord = 1;
            wordCount++;
        }
        if (c == '\n') {
            lineCount++;
        }
    }
    fclose(file);
    printf("字符數：%d\n", charCount);
    printf("單詞數：%d\n", wordCount);
    printf("行數：%d\n", lineCount);
    return 0;
}

圖形界面應用程序（借助圖形庫）

1. 簡單繪圖程序（使用Windows控制臺圖形模式或Linux下的ncurses庫等）
   • Windows控制臺圖形模式示例（繪制矩形）：

     #include <windows.h>

void drawRectangle(int x, int y, int width, int height) { HANDLE hConsole = GetStdHandle(STD_OUTPUT_HANDLE); COORD pos;

for (int i = 0; i < height; i++) {
    pos.Y = y + i;
    for (int j = 0; j < width; j++) {
        pos.X = x + j;
        SetConsoleCursorPosition(hConsole, pos);
        if (i == 0 || i == height - 1 || j == 0 || j == width - 1) {
            printf("*");
        } else {
            printf(" ");
        }
    }
}

int main() { drawRectangle(10, 5, 20, 10); return 0; }

   - **ncurses庫示例（在Linux下繪制簡單圖形）**：
```c
#include <ncurses.h>
int main() {
    initscr();
    noecho();
    cbreak();
    move(10, 20);
    addch('*');
    refresh();
    getch();
    endwin();
    return 0;
}

2. 小游戲（如貪吃蛇）
   • 功能：實現經典的貪吃蛇游戲，蛇可以在屏幕上移動、吃食物并增長身體,撞到墻壁或自己身體則游戲結束。
   • 示例代碼（部分關鍵代碼）：

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

define WIDTH 80

define HEIGHT 20

typedef struct { int x, y; } Point;

typedef struct { Point *body; int length; int direction; } Snake;

typedef struct { Point pos; } Food;

void setup(Snake snake, Food food); void draw(Snake snake, Food food); void input(Snake snake); void logic(Snake snake, Food *food);

int main() { Snake snake; Food food; setup(&snake, &food);

while (1) {
    draw(&snake, &food);
    input(&snake);
    logic(&snake, &food);
    Sleep(100);
}
free(snake.body);
return 0;

void setup(Snake snake, Food food) { snake->length = 5; snake->body = (Point )malloc(snake->length sizeof(Point)); snake->direction = 0; // 0:右, 1:下, 2:左, 3:上

for (int i = 0; i < snake->length; i++) {
    snake->body[i].x = WIDTH / 2 - i;
    snake->body[i].y = HEIGHT / 2;
}
srand(time(NULL));
food->pos.x = rand() % WIDTH;
food->pos.y = rand() % HEIGHT;

void draw(Snake snake, Food food) { system("cls"); for (int i = 0; i < HEIGHT; i++) { for (int j = 0; j < WIDTH; j++) { int isSnake = 0; for (int k = 0; k < snake->length; k++) { if (snake->body[k].x == j && snake->body[k].y == i) { isSnake = 1; break; } } if (isSnake) { printf("O"); } else if (i == food->pos.y && j == food->pos.x) { printf("X"); } else { printf(" "); } } printf("\n"); } }

void input(Snake *snake) { if (GetAsyncKeyState(VK_UP) && snake->direction != 1) { snake->direction = 3; } else if (GetAsyncKeyState(VK_DOWN) && snake->direction != 3) { snake->direction = 1; } else if (GetAsyncKeyState(VK_LEFT) && snake->direction != 0) { snake->direction = 2; } else if (GetAsyncKeyState(VK_RIGHT) && snake->direction != 2) { snake->direction = 0; } }

void logic(Snake snake, Food food) { for (int i = snake->length - 1; i > 0; i--) { snake->body[i] = snake->body[i - 1]; }

switch (snake->direction) {
    case 0:
        snake->body[0].x++;
        break;
    case 1:
        snake->body[0].y++;
        break;
    case 2:
        snake->body[0].x--;
        break;
    case 3:
        snake->body[0].y--;
        break;
}
if (snake->body[0].x < 0 || snake->body[0].x >= WIDTH || snake->body[0].y < 0 || snake->body[0].y >= HEIGHT) {
    exit(0);
}
for (int i = 1; i < snake->length; i++) {
    if (snake->body[0].x == snake->body[i].x && snake->body[0].y == snake->body[i].y) {
        exit(0);
    }
}
if (snake->body[0].x == food->pos.x && snake->body[0].y == food->pos.y) {
    snake->length++;
    snake->body = (Point *)realloc(snake->body, snake->length * sizeof(Point));
    srand(time(NULL));
    food->pos.x = rand() % WIDTH;
    food->pos.y = rand() % HEIGHT;
}

以上只是C語言編寫小軟件的一些簡單示例，C語言還可以用于編寫更復雜的系統工具、網絡程序等。