Module 1 review: sections 1.1 to 1.5

1.1 Computer programs

A computer does nothing on its own. A program is what puts it to work.

A program is a list of very simple instructions, together with the data those instructions act on. The computer follows the list exactly and very quickly. The same machine can play music, show a web page, or add up a column of numbers, because each of those jobs is a different program loaded into the same hardware.

Three words the quiz expects you to keep straight:

• Hardware is the physical equipment: the chips, the drive, the screen.
• Software is the collection of programs that run on the hardware.
• Programming is the work of designing and writing those programs. A person who does it is a programmer.

1.2 The anatomy of a computer

You do not need to be an engineer, but you should know the main parts and what each one is for.

• The CPU, or central processing unit, does the actual work: arithmetic, comparisons, and moving data around. It runs one simple instruction at a time, but billions of them per second.
• Memory, also called RAM or primary storage, holds the program and its data while the program runs. It is fast. It is also volatile, which means it loses everything when the power goes off.
• Secondary storage is the hard disk or solid state drive. It is slower than memory, but it keeps your files when the machine is off.
• Input and output devices, such as the keyboard, screen, and network card, move data between you and the machine.
• A bus is the set of connections that lets these parts pass data back and forth.

To run a program, the computer first copies it from secondary storage into memory, and then the CPU works through it step by step.

1.3 The Python programming language

Where Python came from, and what "high level" means.

Python was written by Guido van Rossum and first released in 1991. The name comes from the British comedy group Monty Python, not the snake.

Python is a high level language. You write instructions that read a little like English and ordinary math, and a separate program called the interpreter turns them into the tiny steps the CPU understands. You never have to write CPU instructions yourself.

Python is clean and quick to read, which is why it is a common first language. It is not a teaching toy. It is used every day for data analysis, science, web servers, and automation. In this course we use Python 3.

1.4 Becoming familiar with your programming environment

Where your code lives and how you run it.

You write a Python program as plain text in an editor and save it in a file whose name ends in .py. The text you write is called the source code.

Most people work in an IDE, an integrated development environment, which puts the editor, a way to run the program, and tools for finding mistakes in one window. When your program produces text, it appears in a panel called the console or terminal.

Two habits the book pushes from the first day: back up your work often, and keep backup copies of earlier versions. A lost file is a lost afternoon.

1.5 Analyzing your first program

The traditional first program prints one line of text. Every word of it is worth naming.

print("Hello, World!")

• print is a function, a named operation that is already built into Python.
• The parentheses hold what you hand to the function. Each value you hand it is an argument.
• "Hello, World!" is a string, which is just text inside quotation marks. It is the argument here.

A few rules that show up on the quiz:

• Statements run in order, from the top of the file to the bottom, one statement per line.
• The exact rules for how code must be written are the language's syntax. Break one and you get a syntax error, and the program will not run at all.
• print() with nothing in the parentheses prints an empty line.
• You can print several values at once by separating them with commas: print("Total:", 42).

Quick check