diff --git a/【实践课内】5.循环结构2/7-1 循环-sum.c b/【实践课内】5.循环结构2/7-1 循环-sum.c
new file mode 100644
index 0000000..41ccb76
--- /dev/null
+++ b/【实践课内】5.循环结构2/7-1 循环-sum.c	
@@ -0,0 +1,33 @@
+#include <stdio.h>
+
+int main() {
+    int n, sum_pos = 0, sum_neg = 0;
+
+    scanf("%d", &n);
+
+    for (int i = 1; i <= n; i++) {
+        int x;
+
+        scanf("%d", &x);
+
+        if (x > 0) {
+            sum_pos += x;
+        } else if (x < 0) {
+            sum_neg += x;
+        }  // when x == 0, do nothing
+    }
+
+    if (sum_pos == 0) {
+        printf("no positive number ");
+    } else {
+        printf("%d ", sum_pos);
+    }
+
+    if (sum_neg == 0) {
+        printf("no negative number\n");
+    } else {
+        printf("%d\n", sum_neg);
+    }
+
+    return 0;
+}
diff --git a/【实践课内】5.循环结构2/7-1 循环-sum.jpg b/【实践课内】5.循环结构2/7-1 循环-sum.jpg
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diff --git a/【实践课内】5.循环结构2/7-2 循环-奇怪的斐波那契数列.c b/【实践课内】5.循环结构2/7-2 循环-奇怪的斐波那契数列.c
new file mode 100644
index 0000000..e47a88a
--- /dev/null
+++ b/【实践课内】5.循环结构2/7-2 循环-奇怪的斐波那契数列.c	
@@ -0,0 +1,22 @@
+#include <stdio.h>
+
+int main() {
+    int n, f,
+        f_pre2 = 7, f_pre1 = 11;
+
+    scanf("%d", &n);
+
+    for (int i = 2; i <= n; i++) {
+        f = (f_pre1 + f_pre2) % 3;
+        f_pre2 = f_pre1;
+        f_pre1 = f;
+    }
+
+    if (f == 0) {
+        printf("YES\n");
+    } else {
+        printf("NO\n");
+    }
+
+    return 0;
+}
diff --git a/【实践课内】5.循环结构2/7-2 循环-奇怪的斐波那契数列.jpg b/【实践课内】5.循环结构2/7-2 循环-奇怪的斐波那契数列.jpg
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diff --git a/【实践课内】5.循环结构2/7-3 循环-字符统计.c b/【实践课内】5.循环结构2/7-3 循环-字符统计.c
new file mode 100644
index 0000000..9447021
--- /dev/null
+++ b/【实践课内】5.循环结构2/7-3 循环-字符统计.c	
@@ -0,0 +1,22 @@
+#include <stdio.h>
+
+int main() {
+    int sum_alpha = 0, sum_digit = 0, sum_space = 0, sum_other = 0;
+    char c;
+
+    while (scanf("%c", &c) != EOF && c != '\n') {
+        if (('A' <= c && c <= 'Z') || ('a' <= c && c <= ' z')) {  // isalpha(c)
+            sum_alpha++;
+        } else if ('0' <= c && c <= '9') {  // isdigit(c)
+            sum_digit++;
+        } else if (c == ' ') {
+            sum_space++;
+        } else {
+            sum_other++;
+        }
+    }
+
+    printf("%d %d %d %d\n", sum_alpha, sum_space, sum_digit, sum_other);
+
+    return 0;
+}
diff --git a/【实践课内】5.循环结构2/7-3 循环-字符统计.jpg b/【实践课内】5.循环结构2/7-3 循环-字符统计.jpg
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diff --git a/【实践课内】5.循环结构2/7-4 循环-直角三角形的输出.c b/【实践课内】5.循环结构2/7-4 循环-直角三角形的输出.c
new file mode 100644
index 0000000..572f784
--- /dev/null
+++ b/【实践课内】5.循环结构2/7-4 循环-直角三角形的输出.c	
@@ -0,0 +1,17 @@
+#include <stdio.h>
+
+int main() {
+    int n;
+
+    scanf("%d", &n);
+
+    for (int i = n; i >= 1; i--) {
+        for (int j = 1; j <= i; j++) {
+            printf("*");
+        }
+
+        printf("\n");
+    }
+
+    return 0;
+}
diff --git a/【实践课内】5.循环结构2/7-4 循环-直角三角形的输出.jpg b/【实践课内】5.循环结构2/7-4 循环-直角三角形的输出.jpg
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