Rama 2 by Arthur C. Clarke and Gentry Lee

Wakefield smiled and continued, watching Nicole carefully to ensure that she was following his explanation. “Apparently, when Janos fell and his fingers hit the control box, he generated three commands. At least that’s what RoSur thought; it was told that there were three manual commands in it’s queue. Of course they were all garbage. But RoSur had no way of know­ing this.

“Maybe now you can appreciate some of the nightmares that plague sys­tem software designers. There’s just no way anybody could ever anticipate all possible contingencies. The designers had protected against one inadvertent garbage command—someone brushing the control box during an operation, for example—but not several bad commands. Manual commands were essen­tially considered to be emergencies by the overall system design. Hence they had the highest priority in the interrupt structure of the RoSur software and were always processed immediately, The design acknowledged, however, that there could be a single ‘bad’ manual command and had the capability of rejecting it and moving on to the next priority interrupts, which included fault protection.”

“Sorry,” said Nicole. “You’ve lost me. How could a design be structured to disregard a single bad command, but not several? I thought this simple processor operated in series.”

Richard turned to his portable computer and, working from notes, called up on the monitor a mass of numbers arrayed in rows and columns. “Here are the operations, instruction by instruction, that the RoSur software imple­mented after there were manual commands in its queue.”

“They repeat,” Janos observed, “every seven operations.”

“Exactly,” Richard replied. “RoSur tried three times to process the first manual command, was unsuccessful in each attempt, and then went on to the next command. The software operated exactly as it was designed—”

“But why,” Tabori asked, “did it go back to the first command after­ward?”

“Because the software designers never considered the possibility of multi­ple bad manual commands. Or at least never designed for the condition. The internal question the software asks after finishing with the processing of each command is whether or not there is another manual command in the buffer. If there is not, then the software rejects the first command and is free to handle another interrupt. If there is, however, the software is told to store the rejected command and process the next command. Now, if two com­mands in a row are rejected, the software assumes that the command proces­sor hardware is broken, swaps to the redundant hardware set, and tries again to process the same manual commands. You can understand the reasoning. Suppose one . . .”

Nicole listened for several seconds as Richard and Janos talked about redundant subsystems, buffered commands, and queue structures. She had very little training in either fault protection or redundancy management and could not follow the exchange. “Just a moment,” she interjected at length, “you’ve lost me again. Remember, I’m not an engineer. Can’t somebody give me a summary in normal English?”

Wakefield was apologetic. “Sorry, Nicole,” he said. “You know what an interrupt-driven software system is?” She nodded. “And you are familiar with the way priorities operate in such a system? Good. Then the explana­tion is simple. The fault protection interrupts based on the accelerometer and imaging data were lower priority than the manual commands inadver­tently entered by Janos when he was falling. The system became locked in a software loop trying to process the bad commands and never had a chance to heed the fault signals from the sensor subsystems. That’s why the scalpel kept cutting.”

For some reason Nicole was disappointed. The explanation was clear enough, and she had certainly not wanted the analysis to implicate Janos or any other member of the crew. But it was too simple. It had not been worth all her time and energy.

Nicole sat down on the cot in Richard Wakefield’s hut. “So much for my mystery,” she said.

Janos sat beside her. “Cheer up, Nicole,” he said. “This is good news. At least now we know for certain that we didn’t foul up the initialization pro­cess. There’s a logical explanation for what happened.”

“Great,” she replied sarcastically. “But General Borzov is still dead. And now Reggie Wilson is too.” Nicole thought about the American journalist’s erratic behavior over the last several days and remembered her earlier conver­sation with Francesca. “Say,” she said spontaneously, “did either of you ever hear General Borzov complain of headaches or any other discomfort? Espe­cially on the day of the banquet?”

Wakefield shook his head. “No,” said Janos. “Why do you ask?”

“Well, I asked the portable diagnostician, based on Borzov’s biometry data, to give me the possible causes of his symptoms, given that the general was not having an appendicitis. The most likely cause was listed as drug reaction. Sixty-two percent probable. I thought that maybe he might have had an adverse reaction to some medication.”

“Really?” Janos said, his curiosity piqued. “Why have you never said anything about this to me before?”

“I was going to … several times,” Nicole answered. “But I didn’t think you were interested. Remember when I stopped by your room on the New­ton the day after General Borzov died? It was right after the crew meeting. From the way you responded I concluded that you didn’t want to rehash—”

“Goodness.” Janos shook his head. “How we humans fail to communi­cate. It was just a headache. Nothing more or less. I certainly didn’t mean to give you the impression that I was unwilling to talk about Valeriy’s death.”

“Speaking of communicating,” Nicole said as she rose wearily from the cot, “I must go to see Dr. Brown and Admiral Heilmann before I go to bed.” She looked at Wakefield. “Thanks a lot for your help, Richard. I wish I could say that I felt better now.”

Nicole walked over beside Janos. ‘Tm sorry, friend,” she said. “I should have shared my whole investigation with you. It probably would have been over much faster—”

^ “It’s fine,” Janos replied. “Don’t worry about it.” He smiled. “Come on, I’ll walk with you as far as my suite.”

Nicole could hear the loud conversation inside before she knocked on the door to the hut. David Brown, Otto Heilmann, and Francesca Sabatini were arguing about how to reply to the latest directions from Earth.

“They’re overreacting,” Francesca was saying. “And they’ll realize it as soon as they have some time to reflect. This is not the first mission to suffer a loss of human life. They didn’t cancel the American space shuttle when that schoolteacher and her crew were killed.”

“But they have ordered us to return to the Newton as soon as possible/’ Admiral Heilmann protested.

“So tomorrow we’ll talk to them again and explain why we want to survey New York first. Takagishi says the sea will start to melt in another day or two and we’ll have to leave anyway. Besides, Wakefield and Takagishi and I did hear something that night, even if David doesn’t believe us.”

“I don’t know, Francesca,” Dr. Brown was starting to respond when he finally heard Nicole’s knock. “Who’s there?” he asked crossly.

“Cosmonaut des Jardins, I have some important medical information—”

“Look, des Jardins,” Brown interrupted quickly, “we’re very busy. Can’t it wait until morning?”

All right, Nicole said to herself. I can wait until morning. She wasn’t anxious to answer Dr. Brown’s questions about Takagishi’s heart condition anyway. “Roger,” she said out loud, laughing at herself for using the expres­sion.

Within seconds Nicole could hear the discussion start again behind her. She walked slowly back to her hut. Tomorrow has to be a better day, she said as she crawled onto her cot.

31 ORVIETO PRODIGY

Good night, Otto,” David Brown said as the German admiral left his hut. “See you in the morning.” Dr. Brown yawned and stretched. He looked at his watch. It was a little more than eight hours until the lights should come on again.

He pulled off his flight suit and had a drink of water. He had just laid down on his cot when Francesca entered his hut. “David,” she said, “we have more problems.” She walked over and gave him a short kiss. “I’ve been talking to Janos. Nicole suspects that Valeriy was drugged.”

“Whaaat?” he replied. He sat up on his cot. “How could she? There was no way—”

“Apparently there was some evidence in his biometry data and she clev­erly found it. She mentioned it to Janos tonight.”

“You didn’t react when he told you, did you? I mean, we must be abso­lutely—”

“Of course not,” Francesca answered. “Anyway, Janos would never sus­pect anything in a thousand years. He is a total innocent. At least where things like this are concerned.”

“Damn that woman,” David Brown said. “And damn her biometry.” He rubbed his face with his hands. “What a day. First that stupid Wilson tries to be a hero. Now this. … I told you we should have destroyed all the data from the operation. It would have been an easy matter to wipe out the central files. Then things would never—”