get started on homework12

hw12/README.md

@@ -0,0 +1,78 @@
+#### 12.16
+```c
+#include "csapp.h"
+void *thread(void *vargp);
+
+int main(int argc, char **argv) 
+{
+    int n = atoi(argv[1]);
+    if (n <= 0) {
+        fprintf(stderr, "Number of threads must be a positive integer.\n");
+        exit(1);
+    }
+
+    pthread_t *tids = (pthread_t *)Malloc(n * sizeof(pthread_t));
+
+    for (int i = 0; i < n; ++i)
+        Pthread_create(&tids[i], NULL, thread, NULL);
+
+    for (int i = 0; i < n; ++i)
+        Pthread_join(tids[i], NULL);
+
+    Free(tids);
+    exit(0);
+}
+
+void *thread(void *vargp) /* Thread routine */
+{
+    printf("Hello, world!\n");
+    return NULL;
+}
+```
+
+#### 12.17
+
+#### 12.18
+
+#### 12.19
+
+#### 12.20
+
+#### 12.21
+
+#### 12.22
+
+#### 12.23
+
+#### 12.24
+
+#### 12.25
+
+#### 12.26
+
+#### 12.27
+
+#### 12.28
+
+#### 12.29
+
+#### 12.30
+
+#### 12.31
+
+#### 12.32
+
+#### 12.33
+
+#### 12.34
+
+#### 12.35
+
+#### 12.36
+
+#### 12.37
+
+#### 12.38
+
+#### 12.39
+