Your first explainable program

15-minute session: read for 3 minutes, trace for 3, experiment for 7, and complete the check for 2. Spend longer whenever you need.

A program is a set of instructions. Read the example from its entry point to the output statement. Text in quotes is data; the output operation is an instruction. Predict the printed line before running. Change only the message, run again, then remove one required punctuation mark and read the first error. Restore the working source.

puts prints a line. def and end delimit a method. each yields values to a block. An instance variable beginning with @ belongs to an object; two objects can hold different values.

puts "Ready"

Expected result: Ready

Practice and evidence

Keep three notes: your prediction, the actual result, and why they match or differ. The completion check grades understanding; the practice task builds skill.

Language reference