完结第三章

Chapter3/IO/getchar_putchar.c

@@ -0,0 +1,11 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+int main()
+{
+    int ch;
+    ch = getchar();
+    putchar(ch);
+
+    exit(0);
+}

Chapter3/IO/gets_puts.c

@@ -0,0 +1,13 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#define STRSIZE 32
+
+int main()
+{
+    char str[STRSIZE];
+    gets(str);
+    puts(str);
+
+    exit(0);
+}

Chapter3/IO/test.c

@@ -0,0 +1,91 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+
+#define WEIGHT 3.0e-23
+#define KQ 950
+
+static void water(void)
+{
+    float num;
+    float sum;
+
+    printf("Please input for num:");
+    scanf("%f", &num);
+
+    if (num <= 0)
+    {
+        fprintf(stderr, "Input Error!\n");
+        exit(1);
+    }
+    sum = num * KQ / WEIGHT;
+
+    printf("Total = %e\n", sum);
+
+    return;
+}
+
+static void area(void)
+{
+    float a, b, c;
+    float s, area;
+
+    printf("Please input:");
+    scanf("%f%f%f", &a, &b, &c);
+    // 对scanf做好校验是好习惯
+    if (a + b <= c || b + c <= a || a + c <= b)
+    {
+        fprintf(stderr, "EINVAL!\n");
+        exit(0);
+    }
+
+    printf("a = %f\n", a);
+    printf("b = %f\n", b);
+    printf("c = %f\n", c);
+
+    // s = 1 / 2 * (a + b + c);
+    s = 1.0 / 2 * (a + b + c);
+    printf("s = %f\n", s);
+    // s=0.000000
+    // 1 / 2是int型计算，得到的是商0余1
+
+    area = sqrt(s * (s - a) * (s - b) * (s - c));
+    printf("area = %f\n", area);
+}
+
+void root(void)
+{
+    float a, b, c;
+    float disc;
+    float p, q;
+    float x1, x2;
+
+    printf("Please input :\n");
+    scanf("%f%f%f", &a, &b, &c);
+
+    if (b * b - 4 * a * c < 0)
+    {
+        fprintf(stderr, "EINVAL\n");
+        exit(1);
+    }
+    disc = b * b - 4 * a * c;
+    p = -b / 2 * a;
+    q = sqrt(disc) / 2 * a;
+
+    x1 = p + q;
+    x2 = p - q;
+
+    printf("x1 = %f\n", x1);
+    printf("x2 = %f\n", x2);
+}
+
+int main()
+{
+    // water();
+
+    // area();
+
+    root();
+
+    exit(0);
+}