修改文件结构。

POP/14/Exercise02.c

@@ -0,0 +1,31 @@
+#include <stdio.h>
+
+char toUpper(char input) {
+    if (input >= 'a') {
+        return input - 'a' + 'A';
+    }
+    else {
+        return input;
+    }
+}
+
+int main() {
+    char ch;
+    FILE* fl;
+    fl = fopen("upper.txt", "w+");
+    while (1) {
+        ch = getchar();
+        if (ch == '#') {
+            break;
+        } 
+        fprintf(fl, "%c", toUpper(ch));
+    }
+    fflush(fl);
+    // fclose(fl);
+    // fl = fopen("upper.txt", "r");
+    rewind(fl);
+    while(!feof(fl)) {
+        putchar(fgetc(fl));
+    }
+    return 0;
+}