CS I · Wed Oct 28 · 13.3 · Do Now

Where Java Came From

Terminology and concepts to look out for: programming language · source code · compiler
Relevance to me: Yesterday you saw that programs written by people carry a question to a model and carry the answer back. Today you find out where one of the languages those programs are written in, Java, came from.
Board Question: People write code using words like print and if, but a computer's chip runs only very simple instructions made of numbers. What do you think happens in between? Give your guess in one sentence, and say whether a person or a program does that step.

Get your question code on the right, then answer Section 1 of the Board Question form in complete sentences.

Board Question

Paste the code into the Question code box of the Board Question form. Then answer Section 1 in complete sentences that restate the question. Keep the form open: you answer Section 2 after table talk.

The Board Question form is not linked yet. Write your answer in your lab notebook, in complete sentences.

Announcements

Programming Languages and Where Java Came From

1 This section explains what a programming language is, how a person's code becomes something a computer can run, and where the Java language came from.

Programming Languages

2 On October 14, the class read that a program is a set of instructions that a person wrote, while a model is trained on examples. Monday's passage showed that everything in an AI tool except the model is an ordinary program, written by people in a programming language.

3 A programming language is a set of words, symbols and rules for writing instructions that a computer can carry out. Each programming language has strict rules about how a statement is built and which symbols may appear in it. A statement in a programming language is designed to have exactly one meaning, wherever it appears. English is not a programming language, because nobody designed it for computers and many English sentences can mean two different things. For example, "The coach saw the player with the camera" does not say who has the camera, so a computer could not run it. Java is one programming language, and Python and JavaScript are two others.

Source Code and the Compiler

4 Source code is the text that a person writes in a programming language. It is meant to be read by people as well as by the computer. In Java, source code is saved in plain text files whose names end in .java. The short program below is Java source code that a person could type into a file named Main.java. The class will read code like this in November.

1public class Main {
2    public static void main(String[] args) {
3        System.out.println("Hello from McDonogh 35");
4    }
5}

Hello from McDonogh 35

5 A compiler is a program that reads source code, checks that it follows the language's rules, and turns it into a form the computer can run. Java's compiler is a program called javac. First, a person saves the source code as Main.java. Next, the person runs javac on that file. Then javac checks every statement against the rules of Java. If a rule is broken, such as a missing semicolon, javac reports an error with its line number and makes no new file. If there are no errors, javac writes a new file named Main.class, which the computer can run.

6 The person writes the source code, and the compiler does the turning. A compiler is not the person who wrote the program, because it only checks and turns instructions that a person already wrote. The Main.class file is not source code either, because the compiler made it and no person typed it. Figure 1 shows these steps as three boxes.

Where Java Came From

7 Java began inside a small research group at Sun Microsystems called the Green Project. In a 2019 interview, James Gosling said the project started at the very end of 1990 and ended in September 1992. The group studied consumer electronics such as TVs and VCRs. Gosling, often called the father of Java, was the only member who had built a compiler before. He volunteered to make the C language safer for those devices, and that work grew into a new language. According to his own account, he named the language Oak after an oak tree outside his office window.

8 The devices the group studied were built with many different kinds of chips. A company that changed to a new chip often had to rewrite large parts of its code. For this reason, the group wanted code that could move to a different chip without being rewritten. Trademark lawyers found too many conflicts with the name Oak, so the team chose the name Java instead. Sun introduced Java to the public on May 23, 1995. Java later became known for the slogan "write once, run anywhere," which Gosling has described as a marketing line. Oracle completed its purchase of Sun on January 27, 2010, and Oracle now looks after Java.

Java and JavaScript

9 Java and JavaScript are two different programming languages. JavaScript was created at Netscape in 1995 by Brendan Eich. In December 1995, Netscape and Sun announced the name JavaScript as part of a partnership between the two companies. The companies linked the two names, even though the designs of the languages were only alike on the surface. Mozilla's documentation tells readers not to confuse the two languages, and it notes that both names are trademarks of Oracle. In this class, Java code is always called Java. The next lesson explains why so many people chose Java and what "write once, run anywhere" means.

Summary

10 A programming language is a set of words, symbols and rules for writing instructions, and source code is the text a person writes in one. A compiler such as javac checks source code against the language's rules and turns it into a form the computer can run. Java began in Sun's Green Project under the name Oak, was introduced in 1995, and has been looked after by Oracle since 2010.

Sources: Oracle, The Java Tutorials: About the Java Technology; Oracle, The javac Command (Java SE 21); Oracle, The Java Tutorials: Common Problems; Downey and Mayfield, Think Java (2020); Downey, Think Python, 2nd ed.; Gosling, Oral History of James Gosling (Computer History Museum, 2019); Krill, Java turns 30 (InfoWorld, 2025); Wirfs-Brock and Eich, JavaScript: The First 20 Years (2020); Oracle, Oracle Completes Acquisition of Sun (2010); Oracle, Java Software; Mozilla, JavaScript (MDN Web Docs).

I Do questions

Nine questions, like the ACT. Use the paragraph numbers. Each question takes one answer, so read all four choices first. Your score and the reasons come at the end.

The main purpose of the passage is to:
According to paragraph 5, what does javac do when a rule of Java is broken?
As it is used in paragraph 3 ("strict rules about how a statement is built"), the word strict most nearly means:
The sentence "The coach saw the player with the camera" (paragraph 3) mainly serves to:
Based on paragraph 6, which of these is source code?
According to the passage, which of these events happened FIRST?
According to paragraph 8, the Green Project wanted code that could move to a different chip without being rewritten because:
According to paragraph 9, Java and JavaScript are connected because:
The passage says Gosling "has described" the slogan "write once, run anywhere" as a marketing line (paragraph 8). The author most likely includes this detail to suggest that the slogan:

Figure 1. Java's story runs from the Green Project at Sun in 1991 to Oracle today, and a person's source code passes through a compiler to become a form the computer can run.

I Do questions

The I Do questions are beside the passage, on the slide before this one. Go back when you are ready to answer.

Programming Languages and Where Java Came From

1 This section explains what a programming language is, how a person's code becomes something a computer can run, and where the Java language came from.

Programming Languages

Source Code and the Compiler

1public class Main {
2    public static void main(String[] args) {
3        System.out.println("Hello from McDonogh 35");
4    }
5}

Hello from McDonogh 35

Where Java Came From

Java and JavaScript

Summary

Table Talk

Revisit your response to the Board Question.

Discuss with your table or partner if possible.

People write code using words like print and if, but a computer's chip runs only very simple instructions made of numbers. What do you think happens in between? Give your guess in one sentence, and say whether a person or a program does that step.

Chromebooks stay closed while you talk. Then answer Section 2 of the Board Question form right here under My View, in complete sentences, and submit it. This is the last time you answer today's Board Question.

Open the I Do form

This form has three sections. Section 1: your first answer to the Board Question. Section 2: nine reading questions on the passage, like the ACT. Section 3: the Board Question one last time, at the end of the I Do.

CR 1. Board Question: People write code using words like print and if, but a computer's chip runs only very simple instructions made of numbers. What do you think happens in between? Give your guess in one sentence, and say whether a person or a program does that step. Give your answer and one reason.

Write your answer in your lab notebook, labeled CR 1.

MC 1. The main purpose of the passage is to:

teach readers how to write and run their first Java program.
argue that Java is a better programming language than JavaScript.
describe James Gosling's whole career at Sun Microsystems.
explain what programming languages and compilers are and trace where Java came from.

MC 2. According to paragraph 5, what does javac do when a rule of Java is broken?

It fixes the error and then writes Main.class.
It deletes the Main.java file.
It reports an error with its line number and makes no new file.
It writes Main.class with a warning at the top.

MC 3. As it is used in paragraph 3 ("strict rules about how a statement is built"), the word strict most nearly means:

old-fashioned.
exact, with no exceptions.
hard to read.
harsh and unkind.

MC 4. The sentence "The coach saw the player with the camera" (paragraph 3) mainly serves to:

show that an English sentence can have more than one meaning.
introduce a program that the class will write about sports.
explain how a camera turns a picture into data.
show that computers can read English if it is written carefully.

MC 5. Based on paragraph 6, which of these is source code?

the lines a student types into a file named Main.java
the javac program itself
the Main.class file that javac writes
the error message javac reports

MC 6. According to the passage, which of these events happened FIRST?

Oracle completed its purchase of Sun.
The Green Project began at Sun Microsystems.
Sun introduced Java to the public.
The team changed the language's name from Oak to Java.

MC 7. According to paragraph 8, the Green Project wanted code that could move to a different chip without being rewritten because:

trademark lawyers required one kind of code for every device.
Sun wanted to sell its own chips to TV companies.
TVs and VCRs needed chips that were faster than computers.
companies that changed to a new chip often had to rewrite large parts of their code.

MC 8. According to paragraph 9, Java and JavaScript are connected because:

James Gosling created both languages at Sun.
JavaScript replaced Java after 1995.
their names were linked by a 1995 partnership, though they are two different languages.
JavaScript is the version of Java that runs on web pages.

MC 9. The passage says Gosling "has described" the slogan "write once, run anywhere" as a marketing line (paragraph 8). The author most likely includes this detail to suggest that the slogan:

proves that Java programs cannot run on more than one kind of computer.
shows that Gosling disliked the language he created.
was written to promote Java, so it should not be read as an exact technical promise.
was invented by Oracle after it bought Sun.

CR 2. Revisit your response to the Board Question. Discuss with your table or partner if possible. People write code using words like print and if, but a computer's chip runs only very simple instructions made of numbers. What do you think happens in between? Give your guess in one sentence, and say whether a person or a program does that step. Give your answer now. Did it stay the same or change? Say what from the reading or your discussion made it stay or change.

Write your answer in your lab notebook, labeled CR 2.