Cook Health Alliance

The Saturn V rocket went to the moon in the summer of 1969. Think about the technology back then and how hard it might have been to program the controls for a rocket that was to fly to the moon and back. The astronauts had not control over the flight of the rocket. It was all done by a computer program dependent on memory made up of individual iron cores that were either magnetized for a “1” or demagnetized for a “0” with the additional knowledge that every time an iron core was accessed, it would demagnetize. The programmer had to remember to rewrite the value into each iron core every time it was accessed.

Videos and Descriptions

YouTube has several good videos describing the memory on the Apollo Saturn V’s. The first one describes the memory module:

and Saturn V Computer ring:

in the rocket itself. The second one describes the Apollo rope memory. Advertisements may come up at the start of the videos, since they do not allow embedding. Skip the ads. I will create a Discussion group in either Teams or D2L to allow you to comment.

Re-entry of Apollo XIII

Apollo 13 had a major catastrophe on its flight to the moon. The final problem was that the heat shield was damaged in the explosion. If it failed, the module would not be able to re-enter. Most re-entries took about three minutes for radio silence. After four minutes of silence, the people in the Houston ground-center became very worried.

Margaret Hamilton

Programming of the Saturn V was difficult. It had room for the large ring containing the computer. Think about the Lunar Lander. Every ounce counted, so the computer had to be much smaller and the program had to be very precise. Margaret Hamilton was the person who had the astronauts lives in her programming skills. She had the privilege of celebrating when the first lunar lander landed and took off safely.

We have already covered console reads from the keyboard and writes to the display using cin and cout. If you do not know how to use cin and cout, please review it before proceeding. ifstream is for an input file connection and an ofstream is for an output file connection. Once set up, they can be used the same as cin and cout respectively. Both ifstream and ofstream are C++ classes and so you need to create an instance of each class in order to use it. You have been using classes throughout your coding work with C++. The one that is easiest to explain is the class “string”. String is a class and the name of your string is the instance of the class. In your header section, it would described as:

string myString = "This is a string."

later in the code, you might want to find its length.

int len = myString.length();           // This finds the length of the string store in your instance of string.

To be fair, there are five different ways to find the length of a string. The first four are more useful than the fifth. https://www.geeksforgeeks.org/5-different-methods-find-length-string-c/

length() is considered a method of the class string and can be called by adding it to the instance of the class string by adding a “.” and then the name of the method to the instance name, as seen in the example above.

Now getting back to ifstream and ofstream.  First create the instance of each class to use.

ofstream outFile;       // define the interface to the file for writing information.
ifstream inFile;        // define the interface to the file for reading information.

The next thing to do is to open the file and seek the start of the file, again done by two methods:

   inFile.open(fileName);
   inFile.seekg(0);

Now to read something from the file one line at a time until no more lines are left in the file and divide up the line into phrases that are separated by commas:

for (string line; getline(inFile, line); ) {   // Read a line, stopping at newline (\n), keep going until EOF (end of file).
       stringstream stream(line);                // Set up the line to be readable through a stream.
      index = 0;
      while (getline(stream, word[index], ',')) {
          cout << headers[index] << word[index] << "\n";
          index++;
      }
      sum += stod(word[2]);
      count++;
 }

Output to a file is even simpler, First open the file. You have to see if the file exists. If it does, give the user the choice to write over the file or append to the file. If the file does not exist, create it.

if (isFileExist(fileName)) {
     // The file exists, so give the user the choice to start a new file or append to the existing file.
     int appendToFile = stoi(input("Do you want to:\n1) Open fresh file?\n2) Append to current file?\nChose"));
     switch (appendToFile)
     {
        case 1:
           outFile.open(fileName);     // Open an existing file, overwriting current content..
           break;
        default:
           outFile.open(fileName, fstream::app); // Open an existing file and allow appending new data.
           break;
      }
}
else outFile.open(fileName, fstream::out);  // Force the creation of the file and then open.

Once you have opened/created the file you can write to it just like you do to the console through cout.

 outFile << employee << "," << birthdate << "," << wages << endl;

The above code will write a comma separated list with three fields to one line in the file. Be sure to close the files when you are done.

outFile.close();
inFile.close();

Celebrating the 4th of July is important to me and others in the United States of America. Each country has special celebrations based on their own history. Ours is declaring independence from England, a treasonous act that could have brought death to each of the signers of the Declaration of Independence. Having an ancestor, Lieutenant Colonel Cornelius Ludlow (who was in charge of General Washington’s rear guard on the move to Valley Forge), it is a doubly important day to me. Unfortunately, a lot of revisionist history has been given out recently. That is a disservice to the memory of those who set the foundation for our nation. Yes, there were actions some of our forefathers did that were not good. But they set the stone in motion that would eventually lead to the emancipation of slaves and the various civil rights that have been put into law more recently.

Two examples of people who were anti-slavery at the time of the American Revelation were Betsy Ross and Edward Coles. Betsy Ross was the creator of the first flag of the United States. Edward Coles is a cousin of one of my ancestors and freed the slaves he inherited.

Betsy Ross grew up as a Quaker, which was opposed to slavery and helped Pennsylvania become the first state to outlaw slavery. Many Presidents, including Barack Obama, used the Betsy Ross flag in their ceremonies.

As you can see by the above picture, the Betsy Ross flag was not controversial at Barack Obama’s Inauguration. He used it to show the heritage of our United States. Betsy Ross was not a slave owner. By all indications, she opposed slavery.

Growing up, I heard the story of Edward Coles long before I knew his name. My mother would tell me about how a group of descendants of freed slaves heard about one of her cousins medical needs and offered support to my mother’s cousin to help him through his struggles. Slavery is wrong. The original Betsy Ross flag shows a field of blue with thirteen stars in a circle. This represents the equality of opportunity for all citizens of the United States. I wish all those who celebrate a wonderful fourth of July. I wish everyone all the freedom and opportunity that you desire.

Happy 4th of July!