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Assembler Tutorial

This program is part of the software suitethat accompanies the book

The Digital Core, by Noam Nisan and Shimon Schocken

2003, www.idc.ac.il/csd, forthcoming by MIT Press

The software suite was developed by students at theEfi Arazi School of Computer Science at IDC

Chief Software Architect: Yaron Ukrainitz

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Translators:

Assembler: translates programs written in the Hack assembly language to executable code written in the Hack machine language;

JcVM (modeled after Java’s JVM): translates programs written in the stack-based Virtual Machine (VM) language to assembly programs;

Jack Compiler: translates programs written in the Java-like Jack language to VM programs that can run on the Virtual Machine.

Simulators:

used to build hardware platforms and execute programs;

supplied by us.

Translators:

Written by the students;

Executable solutions available.

The book’s software suite:

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The book’s software suite:

The Assembler generates binary code that can be tested either in the hardware simulator or in the CPU emulator.

This tutorial describes the Assembler

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Assembler Tutorial

Purpose: learn how to use the supplied Assembler, designed to translate programs from Hack assembly to Hack machine code

Required knowledge: Chapter 5 of the book

Contents:

I. Assembly program example

II. Command-level Assembler

III. Interactive Assembler

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Assembler Tutorial

Part I:

Before we start talking about the Assembler, let’s take a look at a typical assembly program

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Example

/* sum=1+2+ … +100 */@i // i=1M=1@sum // sum=0M=0

(loop)@i // if i-100>0 goto endD=M@100D=D-A@endD;jgt@i // sum+=iD=M@sumM=D+M@I // i++M=M+1@loop // goto loop0;jmp

(end)

/* sum=1+2+ … +100 */@i // i=1M=1@sum // sum=0M=0

(loop)@i // if i-100>0 goto endD=M@100D=D-A@endD;jgt@i // sum+=iD=M@sumM=D+M@I // i++M=M+1@loop // goto loop0;jmp

(end)

sum.asm

000000000001000011101111110010000000000000010001111010101000100000000000000100001111110000010000000000000110010011100100110100000000000000010010111000110000000100000000000100001111110000010000000000000001000111110000100010000000000000010000111111011100100000000000000001001110101010000111

000000000001000011101111110010000000000000010001111010101000100000000000000100001111110000010000000000000110010011100100110100000000000000010010111000110000000100000000000100001111110000010000000000000001000111110000100010000000000000010000111111011100100000000000000001001110101010000111

sum.bin

Assembler

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Example

/* sum=1+2+ … +100 */@i // i=1M=1@sum // sum=0M=0

(loop)@i // if i-100>0 goto endD=M@100D=D-A@endD;jgt@i // sum+=iD=M@sumM=D+M@I // i++M=M+1@loop // goto loop0;jmp

(end)

/* sum=1+2+ … +100 */@i // i=1M=1@sum // sum=0M=0

(loop)@i // if i-100>0 goto endD=M@100D=D-A@endD;jgt@i // sum+=iD=M@sumM=D+M@I // i++M=M+1@loop // goto loop0;jmp

(end)

The assembly process:

Translates Prog.asm into Prog.bin

Comments and white space are ignored

Variables (e.g. i and sum) are allocated to memory

Labels (e.g. loop and end) are psuedo commands that generate no code

Each assembly command is translated into a 16-bit instruction written in the Hack machine language.

The assembly program:

Stored in a text file named Prog.asm

Written and edited in a text editor

sum.asm

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Assembler Tutorial

Purpose: learn how to use the supplied Assembler, designed to translate programs from Hack assembly to Hack machine code

Required knowledge: Chapter 5 of the book

Contents:

I. Assembly program example

II. Command-level Assembler

III. Interactive Assembler

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Assembler Tutorial

Part II:

Learn how to use the Assembler from the operating system’s shell level, batch style.

(the Assembler that you have to write should have the same GUI and behavior)

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The command-level assembler

The OS “type” command can be used to inspect the assembly source (.asm file)

(in your computer the path will probably be different)

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Inspecting the source file

Source code is shown

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Invoking the Assembler

Invoke the Assembler program

Name of the source assembly file (full path). This file name is an argument of the Assembler program.

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The OS “type” command can be used to inspect the translated code(.bin file)

Invoking the Assembler

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Binary code is shown

Inspecting the translated code

Two ways to test the binary code:

1. Invoke the Hardware Simulator, load the Computer chip, then load the code (.bin file) into the internal ROM chip;

2. Load and run the code in the CPU Emulator (much quicker).

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Assembler Tutorial

Purpose: learn how to use the supplied Assembler, designed to translate programs from Hack assembly to Hack machine code

Required knowledge: Chapter 5 of the book

Contents:

I. Assembly program example

II. Command-level Assembler

III. Interactive Assembler

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Hardware Simulation Tutorial

Part III:

Learn how to use the interactive assembler

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Loading an assembly program

1. To load an assembly program, click here.

2. Navigate to a directory and select an .asm file.

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Loading an assembly program

Read-only view of the assembly source code

To edit it, use an external text editor.

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Translating a program

Translate line-by-line

Translate the entire program

Stop the translation

Re-start the translation

Immediate translation(no animation)

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1. Click an assembly command

2. The translated binary code is

highlighted

Inspecting the translation

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Saving the translated code

Saves the translated binary code in a .bin file

If an assembly command contains a syntax error, the translation stops with an error message

The “save file” operation is enabled only if the translation was error-free.

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Comparing the translated code to a compare-file

1. Load a comparison file

2. Select a comparison (.bin) file

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2, Translate the program (any translation mode can be used, as usual)

Comparing the translated code to a compare-file

1. Comparison file is shown

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The translation of the highlighted line does not match the corresponding line in the compare file.

Comparing the translated code to a compare-file

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Mistakes are the portals of discovery

James Joyce (1882-1941)