The assembler

The kind of answer

Enacted. The instruction set is a law the machine keeps from without, never from within. The assembler applies the code exactly as it is written, line by line, as a rule is applied.

On paper first

Turn @17 into sixteen bits. Then turn D=M+1 into sixteen bits with the course’s tables. Check both with the Assembler.

What you build

In the Assembler. The files for Project 6 are in the IDE’s own projects folder, so there is nothing to download.

• Add.asm, translated by hand
• Max.asm, translated by hand
• Rect.asm, translated by hand

Each one is done when its test passes in the IDE. A pass cannot be argued with, and neither can a fail.

Week by week

About an afternoon a week. If a week runs long, let it: the strand keeps its own order, not the calendar’s.

Week	Watch	Do
Week 31	6.1; 6.2; 6.3	What an assembler is, and how each kind of instruction is translated. Translate Add.asm by hand and check it against the Assembler in the IDE.
Week 32	6.4; 6.6B	Symbols: labels and variables. Translate Max.asm by hand, finding the labels first and then everything else, as the lecture does.
Week 33	6.5; 6.6; 6.7	Rect.asm by hand. Lectures 6.5 and 6.6 show how to write an assembler as a program; that is for a second year, so watch them as a look ahead.

The lectures

8 lectures, about 123 minutes in all, by Nisan and Schocken. Watch with your parent, one or two at a sitting.

• 6.1 Assembly Languages and Assemblers 15:29
• 6.2 The Hack Assembly Language 9:05
• 6.3 The Assembly Process: Handling Instructions 11:29
• 6.4 The Assembly Process: Handling Symbols 20:14
• 6.6B Project 6 Overview: Without Programming 9:28
• 6.5 Developing a Hack Assembler 13:57
• 6.6 Project 6 Overview: Programming Option 32:12
• 6.7 Perspectives 11:13

For the parent

The course lets the assembler be written as a program or done by hand, and lecture 6.6B covers the by-hand way. A child who knows Scratch can build a small assembler there, with lists for the course’s tables, but it is not needed. Writing it in a real programming language is for a second year.