Fix: leave fileid 0 and 1 to stdio

code/userprog/ksyscall.h

@@ -47,27 +47,39 @@ OpenFileId SysOpen(char *name) {
         = kernel->fileSystem->Open(name);
       if (kernel->fileSystem->fileDescriptorTable[i] == NULL)
         return -1;
-      return i + 1;  // OpenFileId starts from 1
+      return i + 2;  // OpenFileId starts from 2 (0=stdin, 1=stdout reserved)
     }
   return -1;
 }
 
 int SysWrite(char *buffer, int size, OpenFileId id) {
-  int idx = id - 1;  // Convert 1-based id to 0-based index
+  if (id == 1) {  // Console output (stdout)
+    for (int i = 0; i < size; i++)
+      kernel->synchConsoleOut->PutChar(buffer[i]);
+    return size;
+  }
+  int idx = id - 2;  // Convert to 0-based index (ids 2+ are files)
   if (idx < 0 || idx >= 20 || kernel->fileSystem->fileDescriptorTable[idx] == NULL)
     return -1;
   return kernel->fileSystem->fileDescriptorTable[idx]->Write(buffer, size);
 }
 
 int SysRead(char *buffer, int size, OpenFileId id) {
-  int idx = id - 1;  // Convert 1-based id to 0-based index
+  if (id == 0) {  // Console input (stdin)
+    for (int i = 0; i < size; i++)
+      buffer[i] = kernel->synchConsoleIn->GetChar();
+    return size;
+  }
+  int idx = id - 2;  // Convert to 0-based index (ids 2+ are files)
   if (idx < 0 || idx >= 20 || kernel->fileSystem->fileDescriptorTable[idx] == NULL)
     return -1;
   return kernel->fileSystem->fileDescriptorTable[idx]->Read(buffer, size);
 }
 
 int SysClose(OpenFileId id) {
-  int idx = id - 1;  // Convert 1-based id to 0-based index
+  if (id == 0 || id == 1)  // Cannot close console
+    return 0;
+  int idx = id - 2;  // Convert to 0-based index (ids 2+ are files)
   if (idx < 0 || idx >= 20 || kernel->fileSystem->fileDescriptorTable[idx] == NULL)
     return 0;
   delete kernel->fileSystem->fileDescriptorTable[idx];