How a computer turns input into output, and what makes a set of instructions an algorithm. No code yet: this chapter sets up the vocabulary the rest of the course uses.

Printing text to the screen with print, and the syntax rules that make it work. Four Make exercises build the same joke program under increasingly tight constraints.

Storing data in named variables, replacing that data while the program runs, and joining strings together with concatenation.

Reading what the user types with input, storing it in a variable, and building a response around it.

Arithmetic operators and casting between text and numbers, so a program can calculate with its input instead of only echoing it.

The remainder operator % and the power operator **, and the problems each one solves: leftovers, splitting seconds into minutes, squares and cubes.

Boolean conditions and two-way decisions, letting a program take a different path depending on what it finds.

Chaining conditions with elif so a program can choose between more than two options, and why the order of the branches decides the outcome.

Repeating code with while loops and counters, including loops that keep asking until they get the answer they want.

Repeating code a set number of times with for loops and range. Count controlled iteration: the number of repetitions is known before the loop starts.

Storing many values under one name, reading them back by index, and changing a list while the program runs.

Letting the computer pick: random whole numbers with randint and randrange, a random item from a list with choice, and games built on them.

Working with text: its length, upper and lower case, cutting out substrings with slicing, looping through the characters, and converting to and from ASCII codes.

Data with rows and columns, stored as a list of lists: reading and changing one item with two indices, and visiting every item with nested loops.

Opening a text file and reading it into a program, all at once with a for loop or one line at a time with readline, and using what it holds.

Saving data from a program into a text file: write mode replaces what was there, append mode adds to the end, and every line ends with a newline.

Splitting a program into named subroutines, passing arguments into them, and tracing the order in which they run.