From 7225fec89d7cfbc4516b14778fdceebb90a53699 Mon Sep 17 00:00:00 2001 From: John O'Donnell Date: Fri, 14 Jan 2022 09:09:23 +0000 Subject: [PATCH] main sections for subsets in user guide --- docs/UserGuide/Sigma16UserGuide.html | 1248 +++++++++++++------------- docs/UserGuide/Sigma16UserGuide.org | 70 +- docs/welcome/welcome.html | 30 +- src/base/assembler.mjs | 23 +- src/server/sigserver.mjs | 17 +- 5 files changed, 720 insertions(+), 668 deletions(-) diff --git a/docs/UserGuide/Sigma16UserGuide.html b/docs/UserGuide/Sigma16UserGuide.html index 20a3ebd..0fd9b30 100644 --- a/docs/UserGuide/Sigma16UserGuide.html +++ b/docs/UserGuide/Sigma16UserGuide.html @@ -3,7 +3,7 @@ "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> - + Sigma16 User Guide @@ -243,215 +243,217 @@

Sigma16 User Guide

-Version 3.4.1, December 2021. -Copyright (c) 2021 John T. O'Donnell +Version 3.4.1, January 2022. +Copyright (c) 2022 John T. O'Donnell

Table of Contents

-
-

Introduction

-
+
+

Introduction

+

Sigma16 is a computer architecture designed for research and teaching in computer systems. The architecture is simple yet -powerful. It is organized into subsets to make it easier to use: -the core subset is suitable for beginners, the standard subset -offers flexible programming techniques, and the full system supports -the study of systems programming. +powerful.

@@ -476,23 +478,37 @@

Introduction

-For a quick start, begin with the tutorials, which introduce the -architecture step by step. The tutorials explain the machine, show -how to program it, and demonstrate how to enter and run a program -and how to use the programming environment. +The architecture is organized into subsets to make it easier to use: +

+
    +
  • The Core subset contains a small and simple instruction set which +is a good starting point for learning about computer architecture. +Although it is simple, Core is powerful enough to support realistic +programming.
    • +
  • The Standard subset offers flexible programming techniques, +including flexible manipulation of bits and fields and arithmetic on +natural numbers and arbitrary precision integers.
    • +
  • The full System supports the study of systems programming. It +supports interrupts, concurrent processes, and critical regions.
    • +
+

+Core is a subset of Standard, which is a subset of System. To learn +the architecture, start with Core and then go on to Standard and +System.

-The remainder of the user guide is organised by topic, with chapters -on the architecture, the assembly language, the linker, and -programming techniques. +For a quick start, begin with the Core architecture tutorials, which +introduce the architecture step by step. The tutorials explain the +machine, show how to program it, and demonstrate how to enter and run +a program and how to use the programming environment.

-
-

Tutorials

-
+
+

Core architecture

+

The following short tutorials introduce the system; full details appear in later sections. You can keep the tutorials visible in the @@ -502,13 +518,13 @@

Tutorials

-

Core architecture tutorial

+

Core architecture tutorials

-
-

Hello, world!

-
+
+

Hello, world!

+

Let's begin by running a simple example program. For now, we focus only on how to use the software tools. You don't need to understand @@ -595,9 +611,9 @@

Hello, world!

-
-

A quick tour

-
+
+

A quick tour

+

This tutorial introduces the main components of the architecture as well as the graphical user interface. @@ -685,17 +701,13 @@

A quick tour

-
-

Registers, constants, and arithmetic

-
-

-This tutorial introduces the main components of the app. -

- +
+

Registers, constants, and arithmetic

+

-The architecture has a register file which is an array of 16 -registers, named R0, R1, R2, …, R15. The Register File is displayed -in a box on the Processor page. +Programs do most of their work using the register file, which is +an array of 16 registers named R0, R1, R2, …, R15. The Register +File is displayed in a box on the Processor page.

@@ -719,7 +731,7 @@

Registers, constants, and arithmetic

into a register. For example, to load 42 into register 3, write

-
+
 lea  R3,42[R0]   ; R3 := 42
 

 
@@ -768,7 +780,7 @@ 
Registers, constants, and arithmetic

 into R4:
 

 
-
+
 add   R4,R8,R1  ; R4 := R8 + R1
 

 
@@ -786,7 +798,7 @@ 
Registers, constants, and arithmetic

 The following program calculates 3+4:
 

 
-
+
 lea   R5,3[R0]    ; R5 := 3
 lea   R8,4[R0]    ; R8 := 4
 add   R2,R5,R8    ; R2 := R5 + R8 = 3+4 = 7
@@ -808,7 +820,7 @@ 
Registers, constants, and arithmetic

 register):
 

 
-
+
 add  R4,R11,R0   ; R4 := R11 + R0
 sub  R5,R2,R13   ; R5 := R2 - R13
 mul  R2,R10,R7   ; R2 := R10 * R7
@@ -838,7 +850,7 @@ 
Registers, constants, and arithmetic

 whatever value was previously there.  So consider this example:
 

 
-
+
 lea   R7,20[R0]  ; R7 := 20
 lea   R8,30[R0]  ; R8 := 30
 add   R7,R7,R8   ; R7 := R7 + R8
@@ -874,7 +886,7 @@ 
Registers, constants, and arithmetic

 the number.  Thus $00a5 and 0165 both represent the integer 165.
 
 
-
+
 lea   R1,13[R0]     ; R1 =  13 (hex 000d)
 lea   R2,$002f[R0]  ; R2 := 47 (hex 002f)
 lea   R3,$0012[R0]  ; R3 := 18 (hex 0012)
@@ -918,7 +930,7 @@ 
Registers, constants, and arithmetic

 avoid R0 and R15).
 

 
-
+
 lea  R1,3[R0]   ; R1 := 3
 lea  R2,4[R0]   ; R2 := 4
 lea  R3,5[R0]   ; R3 := 5
@@ -932,7 +944,7 @@ 
Registers, constants, and arithmetic

 There is a special instruction to do this:
 

 
-
+
 trap  R0,R0,R0   ; halt
 

 
@@ -1009,7 +1021,7 @@ 
Registers, constants, and arithmetic

 
  • We wish to compute R5 = (a+b) * (c-d)
    • 
 
 
-
    +
     add   R6,R1,R2     ; R6 := a + b
 sub   R7,R3,R4     ; R7 := c - d
 mul   R5,R6,R7     ; R5 := (a+b) * (c-d)
@@ -1059,9 +1071,9 @@ 
    Registers, constants, and arithmetic
    -
    -

    Keeping variables in memory

    -
    +
    +

    Keeping variables in memory

    +

    So far we have used registers in the register file to hold variables. However, there are only 16 of these, and two have special purposes (R0 @@ -1149,7 +1161,7 @@

    Keeping variables in memory

    Solution:

    -
    +
     load   R1,a[R0]      ; R1 := a
 load   R2,b[R0]      ; R2 := b
 add    R3,R1,R2      ; R3 := a+b
@@ -1190,7 +1202,7 @@ 
    Keeping variables in memory
    
 For example, to define variables x, y, z and give them initial values:
 
    
 
-
    +
     x    data   34    ; x is a variable with initial value 34
 y    data    9    ; y is initially 9
 z    data    0    ; z is initially 0
@@ -1223,7 +1235,7 @@ 
    Keeping variables in memory
    
 and memory are changed.
 
 
-
    +
     ; Program Add.  See Sigma16/README.md in top folder
 ; A minimal program that adds two integer variables
 
@@ -1339,7 +1351,7 @@ 
    Keeping variables in memory
    
 
    
 Here are some syntactically valid statements:
 
    
-
    +
     loop   load   R1,count[R0]    ; R1 = count
        add    R1,R1,R2        ; R1 = R1 + 1
 
    
@@ -1348,7 +1360,7 @@ 
    Keeping variables in memory
    
 Each of the following statements is wrong!
 
    
 
-
    +
        add   R2, R8, R9    ; spaces in the operand field
 loop1  store x[R0],R5  ; wrong order: should be R5,x[R0]
     addemup            ; invalid mnemonic
@@ -1369,7 +1381,7 @@ 
    Keeping variables in memory
    
 fields are what you intended.  For example if you meant to say
 
    
 
-
    +
     add R1,R2,R3  ; x := a + b
 
    
 
@@ -1377,7 +1389,7 @@ 
    Keeping variables in memory
    
 but you have a spurious space, like this
 
    
 
-
    +
     add R1, R2,R3  ; x := a + b
 
    
 
@@ -1405,7 +1417,7 @@ 
    Keeping variables in memory
    
 Examples:
 
    
 
-
    +
        lea   R1,40[R0]      ; R1 = 40
    lea   R2,$ffff[R0]   ; R2 = -1
 
@@ -1451,7 +1463,7 @@ 
    Keeping variables in memory
    
 vertically, like this:
 
    
 
-
    +
     load   R1,three[R0]  ; R1 = 3
 load   R2,x[R0]      ; R2 = x
 mul    R3,R1,R2      ; R3 = 3*x
@@ -1463,7 +1475,7 @@ 
    Keeping variables in memory
    
 Not like this:
 
    
 
-
    +
        load   R1,three[R0]     ; R1 = 3
  load  R2,x[R0] ; R2 = x
       mul R3,R1,R2           ; R3 = 3*x
@@ -1488,9 +1500,9 @@ 
    Keeping variables in memory
    -
    -

    Files and modules

    -
    +
    +

    Files and modules

    +

    Whatever method you use to edit your programs, be sure to save your work to a file from time to time. If you don't do that, sooner or @@ -1617,16 +1629,16 @@

    Files and modules

    -
    -

    Jumps and conditionals

    -
    +
    +

    Jumps and conditionals

    +

    Conditionals allow a program to decide which statements to execute based on Boolean expressions. One example is the if-then statement, for example:

    -
    +
     if x<y
   then statement 1
 statement 2
@@ -1636,7 +1648,7 @@ 
    Jumps and conditionals
    
 A related form is the if-then-else statement:
 
    
 
-
    +
     if x<y
   then statement 1
   else statement 2
@@ -1649,7 +1661,7 @@ 
    Jumps and conditionals
    
 bexp to decide whether to jump to someLabel, or not to jump:
 
    
 
-
    +
     if bexp then goto someLabel
 
    
 
@@ -1657,7 +1669,7 @@ 
    Jumps and conditionals
    
 The commonest case is where bexp is a comparision between two integers:
 
    
 
-
    +
     if x < y then goto someLabel
 
    
 
@@ -1684,7 +1696,7 @@ 
    Jumps and conditionals
    
 is a relation, such as lt, eq, and so on:
 
    
 
-
    +
     jumplt  someLabel[R0]  ; if <  then goto someLabel
 jumple  someLabel[R0]  ; if <= then goto someLabel
 jumpeq  someLabel[R0]  ; if =  then goto someLabel
@@ -1719,7 +1731,7 @@ 
    Jumps and conditionals
    
 address of the sub instruction.
 
    
 
-
    +
     label1   add  R2,R4,R13
 label2
          sub  R15,R0,R1
@@ -1730,7 +1742,7 @@ 
    Jumps and conditionals
    
 similar fixed patterns.  Suppose Bexp is a Boolean in any register Rd
 
    
 
-
    +
     if bexp
   then statement 1
 statement 2
@@ -1742,7 +1754,7 @@ 
    Jumps and conditionals
    
 
    
 
 
-
    +
          if !bexp then goto L1
      statement 1
 L1:
@@ -1754,7 +1766,7 @@ 
    Jumps and conditionals
    
 Her is an example:
 
    
 
-
    +
     a := 93
 x := 35
 y := 71
@@ -1766,7 +1778,7 @@ 
    Jumps and conditionals
    
 The corresponding assembly language is:
 
    
 
-
    +
     ; a := 93
       lea     R1,93[R0]    ; R1 := 93
       store   R1,a[R0]     ; a := 93
@@ -1812,7 +1824,7 @@ 
    Jumps and conditionals
    
 and which doesn't use a Boolean.
 
    
 
-
    +
     jump   somewhere[R0]    ; go to somewhere
 
    
 
@@ -1820,7 +1832,7 @@ 
    Jumps and conditionals
    
 The general form is
 
    
 
-
    +
     if x < y
   then S1
   else S2
@@ -1832,7 +1844,7 @@ 
    Jumps and conditionals
    
 and conditional goto:
 
    
 
-
    +
         if x >= y then goto L1
     S1
     goto L2
@@ -1842,15 +1854,15 @@ 
    Jumps and conditionals
    -
    -

    Loops

    -
    +
    +

    Loops

    +

    Loops are implemented using compilation patterns based on comparisons and jumps. The fundamental form is the while loop.

    -
    +
     while Bexp do S1
 S2
 
    
@@ -1859,7 +1871,7 @@ 
    Loops
    
 The compilation pattern is:
 
    
 
-
    +
     L1   if not Bexp then goto L2
      S2
      goto L1
@@ -1871,7 +1883,7 @@ 
    Loops
    
 expressed as a while loop:
 
    
 
-
    +
     while true do S1
 
    
 
@@ -1879,7 +1891,7 @@ 
    Loops
    
 This doesn't need a Boolean expression; it is simply compiled into:
 
    
 
-
    +
     loop
    instructions for S1
    jump   loop[R0] 
@@ -1937,7 +1949,7 @@ 
    Loops
    
 and the containment may go several levels deep.
 
    
 
-
    +
     if b1
   then S1
        if b2 then S2 else S3
@@ -1979,9 +1991,9 @@ 
    Loops
    -
    -

    Machine language

    -
    +
    +

    Machine language

    +

    The actual bits representing an instruction (written in hex) (e.g 0d69) are machine language. The actual hardware runs the machine @@ -2129,7 +2141,7 @@

    Machine language

    Example of RRR:

    -
    +
     add  R13,R6,R9
 
    
 
@@ -2183,7 +2195,7 @@ 
    Machine language
    
 
    
 Format of RX instruction
 
    
-
    +
     load R1,x[R0]
 
    
 
@@ -2206,7 +2218,7 @@ 
    Machine language
    
 machine code for load R1,x[R0] is:
 
    
 
-
    +
     f101
 0008
 
    
@@ -2256,19 +2268,19 @@ 
    Machine language
    -
    -

    Pseudoinstructions

    -
    -
    +
    
+
    Pseudoinstructions
    
+
    
+
     jumpc0 Rd,disp[Ra]
 
    
 
 
-
    +
     jumpc1 Rd,disp[Ra]
 
    
 
-
    +
     jumplt  someLabel[R0]  ; if <  then goto someLabel
 jumple  someLabel[R0]  ; if <= then goto someLabel
 jumpeq  someLabel[R0]  ; if =  then goto someLabel
@@ -2279,9 +2291,9 @@ 
    Pseudoinstructions
    
 
    
 
    
 
-
    
-
    A strange program
    
-
    
+
    
+
    A strange program
    
+
    
 
    
 Consider ``Program Strange'' below.  This program doesn't compute
 anything particularly useful.  It's rather strange and not a model for
@@ -2309,7 +2321,7 @@ 
    A strange program
    
 
  • y data -5424
    • 
 
 
-
    +
     ; Strange: A Sigma16 program that is a bit strange    
         load   R1,y[R0]
         load   R2,x[R0]
@@ -2483,12 +2495,9 @@ 
    A strange program
    
 
    
 
    
 
-
    
-
    Testing and debugging
    
-
    
-
    
-
    Breakpoints
    
-
    
+
    
+
    Breakpoints
    
+
    
 
    
 Quick summary, explanation follows.  There are two ways to set a
 breakpoint:
@@ -2549,10 +2558,11 @@ 
    Breakpoints
    
 external break is better.
 
    
 
    
+
    
 
-
      
-
    • Trap break
      
-
      
+
      
+
      Trap break
      
+
      
 
      
 You can use a trap instruction to break execution when it executes.
 The first operand of the instruction is a register that must contain
@@ -2564,7 +2574,7 @@ 
      Breakpoints
      
 in this code.
 
      
 
-
      +
       ...
 add    R1,R2,R3
 load   R4,x[R1]
@@ -2579,7 +2589,7 @@ 
      Breakpoints
      
 the break.
 
      
 
-
      +
       ...
 add    R1,R2,R3
 lea    R9,4       ; R9 := trap break code
@@ -2605,10 +2615,11 @@ 
      Breakpoints
      
 Examples / Testing / Looper.
 
      
 
      
-
      • 
+
    
 
-
  • External break
    
-
    
+
    
+
    External break
    
+
    
 
    
 You can also tell the user interface to perform a breakpoint without
 modifying the program.  You need to know the address of the
@@ -2640,14 +2651,13 @@ 
    Breakpoints
    
 popup again and click Disable.
 
    
 
    
-
    • 
-
+
    
 
    
 
 
-
    
-
    Summary of Core Architecture
    
-
    
+
    
+
    Summary of Core Architecture
    
+
    
 
    
 The following table summarises the instructions in the Core subset of
 Sigma16.  This is an extract from the table for the full architecture
@@ -2852,44 +2862,50 @@ 
    Summary of Core Architecture
    
 
    
 
    
 
-
    
-
    Standard architecture tutorial
    
-
    
+
    
+
    Standard architecture
    
 
    
-
    
-
    Logic
    
+
+
    
+
    Standard architecture tutorials
    
+
    
 
    
-
    
-
    Bit fields and shifting
    
+
    
+
    Logic
    
 
    
-
    
-
    Stack instructions
    
+
    
+
    Bit fields and shifting
    
 
    
-
    
-
    Saving registers for procedure call
    
+
    
+
    Stack instructions
    
+
    
+
    
+
    Saving registers for procedure call
    
 
    
 
-
-
    
-
    Arithmetic on natural numbers
    
+
    
+
    Arithmetic on natural numbers
    
 
    
 
    
-
    
-
    Systems architecture tutorial
    
-
    
+
+
    
+
    Systems architecture
    
+
    
 
    
-
    
-
    System control registers
    
+
    
+
    Systems architecture tutorials
    
+
    
 
    
-
    
-
    Interrupt handlers
    
+
    
+
    System control registers
    
 
    
+
    
+
    Interrupt handlers
    
 
    
-
    
-
    S32 architecture tutorial
    
 
    
 
    
 
+
 
    
 
    Sigma16 Architecture reference
    
 
    
@@ -2932,9 +2948,9 @@ 
    Sigma16 Architecture reference
    
 
 
    
 
-
    
-
    Words
    
-
    
+
    
+
    Words
    
+
    
 
    
 Sigma16 uses the following terminology:
 
    
@@ -3038,13 +3054,13 @@ 
    Words
    
 
    
 
    
 
-
    
-
    Bits and fields
    
-
    
+
    
+
    Bits and fields
    
+
    
 
    
-
    
-
    Indexing bits in a word
    
-
    
+
    
+
    Indexing bits in a word
    
+
    
 
    
 Bit positions are numbered from right to left, starting with 0.  The
 rightmost (least significant) bit has index 0, and the leftmost
@@ -3131,9 +3147,9 @@ 
    Indexing bits in a word
    
 
    
 
 
-
    
-
    Memory
    
-
    
+
    
+
    Memory
    
+
    
 
    
 The memory is a hardware array of words that are accessed by address.
 A memory address is 16 bits wide, and there is one memory location
@@ -3169,13 +3185,13 @@ 
    Memory
    
 
    
 
    
 
-
    
-
    Registers
    
-
    
+
    
+
    Registers
    
+
    
 
    
-
    
-
    Register file
    
-
    
+
    
+
    Register file
    
+
    
 
    
 The register file is a set of 16 general registers that hold a 16
 bit word.  A register is referenced by a 4-bit binary number.  In
@@ -3251,8 +3267,8 @@ 
    Register file
    
 
    
 
 
      
-
    • R0 contains the constant 0
      
-
      
+
    • R0 contains the constant 0
      
+
      
 
      
 One of the registers, R0, has a special property: it always contains
 the constant 0.  It is legal to perform an instruction that attempts
@@ -3263,8 +3279,8 @@ 
      Register file
      
 
      
 
      • 
 
-
    • R15 is the condition code register
      
-
      
+
    • R15 is the condition code register
      
+
      
 
      
 Several instructions produce status information: the result of a
 comparison, whether there was an overflow, etc.  This information is
@@ -3456,9 +3472,9 @@ 
      Register file
      
 
    
 
    
 
-
    
-
    Instruction control registers
    
-
    
+
    
+
    Instruction control registers
    
+
    
 
    
 There are several instruction control registers that enable the
 processor to keep track of the state of the running program.  These
@@ -3481,9 +3497,9 @@ 
    Instruction control registers
    
 
    
 
    
 
-
    
-
    System control registers
    
-
    
+
    
+
    System control registers
    
+
    
 
 
 
@@ -3547,8 +3563,8 @@ 
    System control registers
      
-
    • Status register flags
      
-
      
+
    • Status register flags
      
+
      
 
      
 The processor can be executing in several modes, which are determined
 by the system control registers.
@@ -3556,8 +3572,8 @@ 
      System control registers
      
 
      
 
      • 
 
-
    • req and mask registers
      
-
      
+
    • req and mask registers
      
+
      
 
      
 Interrupt request and mask bits (req and mask registers)
 
      
@@ -3669,9 +3685,9 @@ 
      System control registers
      
 
    
 
-
    
-
    Interrupts and exceptions
    
-
    
+
    
+
    Interrupts and exceptions
    
+
    
 
      
 
    • mask
      • 
 
@@ -3686,8 +3702,8 @@ 
      Interrupts and exceptions
      
 
    
 
 
      
-
    • Mask and request flags
      
-
      
+
    • Mask and request flags
      
+
      
 
      
 <table>
   <tr>
@@ -3753,9 +3769,9 @@ 
      Interrupts and exceptions
      
 
      
 
    
 
-
    
-
    Instruction representation
    
-
    
+
    
+
    Instruction representation
    
+
    
 
    
 Instructions are represented in the memory of the computer using
 words, just like all other kinds of data.  From the programmer's
@@ -3918,9 +3934,9 @@ 
    Instruction representation
    
 
    
 
    
 
-
    
-
    RRR format
    
-
    
+
    
+
    RRR format
    
+
    
 
    
 RRR instructions are represented in one word comprising four 4-bit
 fields.
@@ -3958,9 +3974,9 @@ 
    RRR format
    
 
    
 
    
 
-
    
-
    RX format
    
-
    
+
    
+
    RX format
    
+
    
 
    
 RX instructions specify a memory location as well as a register
 operand.  The machine language representation is two words:
@@ -4042,9 +4058,9 @@ 
    RX format
    
 
    
 
    
 
-
    
-
    EXP format
    
-
    
+
    
+
    EXP format
    
+
    
 
    
 An EXP instruction contains 14 (hex e) in the op field, and the a and
 b fields are combined into a single 8-bit number that contains a
@@ -4089,9 +4105,9 @@ 
    EXP format
    
 
    
 
    
 
-
    
-
    EXP3 format
    
-
    
+
    
+
    EXP3 format
    
+
    
 
    
 The EXP3 format uses three words to represent an instruction.  The
 first two words have the same layout as for EXP, and the third word
@@ -4109,13 +4125,13 @@ 
    Instructions
    
 
    
 
    
 
-
    
-
    Arithmetic
    
-
    
+
    
+
    Arithmetic
    
+
    
 
    
 
      
-
    • add
      
-
      
+
    • add
      
+
      
 
      
 The instruction add Rd,Ra,Rb has operands Ra and Rb and
 destination Rd.  It fetches the operands Ra and Rb, calculates
@@ -4169,7 +4185,7 @@ 
      Arithmetic
      
 size 3 consists of the bits x.9 x.8 x.7.
 
      
 
-
      +
       add R1,R2,R3    ; R1 := R2 + R3
 
      
 
@@ -4270,8 +4286,8 @@ 
      Arithmetic
      
 
      
 
      • 
 
-
    • sub
      
-
      
+
    • sub
      
+
      
 
      
 Example: sub R1,R2,R3 ; R1 := R2 - R3
 
      
@@ -4320,8 +4336,8 @@ 
      Arithmetic
      
 
      
 
      • 
 
-
    • mul
      
-
      
+
    • mul
      
+
      
 
      
 Example: mul R1,R2,R3 ; R1 := R2 * R3
 
      
@@ -4354,8 +4370,8 @@ 
      Arithmetic
      
 
      
 
      • 
 
-
    • div
      
-
      
+
    • div
      
+
      
 
      
 Example: div R1,R2,R3 ; R1 := R2 / R3, R15 := R2 rem R3
 
      
@@ -4388,7 +4404,7 @@ 
      Arithmetic
      
 For example:
      • 
 
    
 
-
    +
     div    R1,R2,R3       ; R1 := R2/R3, R15 := R2 rem R3
 cmp    R3,R0       ; Did we divide by 0?
 jumpeq zeroDivide[R0] ; If yes, handle error
@@ -4403,8 +4419,8 @@ 
    Arithmetic
    
 
    
 
 
-
  • addc
    
-
    
+
  • addc
    
+
    
 
    
 The addc instruction performs a binary addition with carry
 propagation.  It adds the two operand registers and the carry bit in
@@ -4416,9 +4432,9 @@ 
    Arithmetic
    
 
    
 
    • 
 
-
  • muln
    
-
    
-
    +
  • muln
    
+
    
+
     muln   Rd,Ra,Rb
 
    
 
@@ -4432,9 +4448,9 @@ 
    Arithmetic
    
 
    
 
    • 
 
-
  • divn
    
-
    
-
    +
  • divn
    
+
    
+
     divn   Rd,Ra,Rb
 
    
 
@@ -4459,9 +4475,9 @@ 
    Arithmetic
    
 
 
    
 
-
    
-
    Logic and bits
    
-
    
+
    
+
    Logic and bits
    
+
    
 
    
 The instructions in this section treat a word as a sequence of bits,
 not as a number.  There are instructions that perform logic operations
@@ -4504,8 +4520,8 @@ 
    Logic and bits
    
 
    
 
 
      
-
    • cmp
      
-
      
+
    • cmp
      
+
      
 
      
 The compare instruction cmp Ra,Rb compares the values in the operand
 registers Ra and Rb, and then sets flags in the condition code
@@ -4536,15 +4552,15 @@ 
      Logic and bits
      
 by a jump pseudoinstruction, for example:
 
      
 
-
      +
       cmp     R4,R9      ; compare R4 with R9
 jumpgt  abc]R0]    ; if R4 > R9 then goto abc
 
      
 
      
 
      • 
 
-
    • logicw
      
-
      
+
    • logicw
      
+
      
 
      
 The logicw instruction performs a bitwise logic operation on two
 operands: each bit of the result is obtained by performing the logic
@@ -4921,8 +4937,8 @@ 
      Logic and bits
      
 
      
 
      • 
 
-
    • logicb
      
-
      
+
    • logicb
      
+
      
 
      
 The logicb instruction performs an arbitrary Boolean logic function
 on two operand bits, producing a result bit.  All three bits must be
@@ -4935,7 +4951,7 @@ 
      Logic and bits
      
 This logicb instruction performs R1.3 := R1.9 xor R1.2:
 
      
 
-
      +
       logicb  R1,3,9,2,6
 logicb  d,e,f,g,h
 
      
@@ -4958,7 +4974,7 @@ 
      Logic and bits
      
 pseudoinstructions:
 
      
 
-
      +
       invb    R1,3,9     ; R1.3 := !R1.9
 andb    R1,3,9,2   ; R1.3 := R1.9 & R1.2
 orb     R1,3,9,2   ; R1.3 := R1.9 | R1.2
@@ -4969,7 +4985,7 @@ 
      Logic and bits
      
 The instruction format is EXP, with the following fields:
 
      
 
-
      +
       logicb  Rd,e,f,g,h
 
      
 
@@ -4984,8 +5000,8 @@ 
      Logic and bits
      
 
      
 
      • 
 
-
    • shiftl, shiftr
      
-
      
+
    • shiftl, shiftr
      
+
      
 
      
 The instruction shiftl Rd,Ra,k shifts the value in the operand
 register Ra by k bits to the left, and the result is placed in the
@@ -4994,7 +5010,7 @@ 
      Logic and bits
      
 rightmost k bits become 0.
 
      
 
-
      +
       shiftl  R2,R3,5
 op = e (EXP format)
 d = 2 (destination register)
@@ -5027,7 +5043,7 @@ 
      Logic and bits
      
 changed.
 
      
 
-
      +
       shiftr  R2,R3,5
 
      
 
@@ -5038,8 +5054,8 @@ 
      Logic and bits
      
 
      
 
      • 
 
-
    • extract, extracti
      
-
      
+
    • extract, extracti
      
+
      
 
      
 The extract instruction copies an arbitrary field of bits from a
 source register and inserts those bits into an arbitrary position in
@@ -5068,7 +5084,7 @@ 
      Logic and bits
      
 statement is:
 
      
 
-
      +
       extract Rd,f,g,Re,h
 
      
 
@@ -5077,7 +5093,7 @@ 
      Logic and bits
      
 the corresponding bit in the source field:
 
      
 
-
      +
       Rd.i := Rs.k
 Rd.i-1 := Rs.k-1
 ...
@@ -5087,7 +5103,7 @@ 
      Logic and bits
      
 
      
 Example:
 
      
-
      +
       extract R2,7,4,R3,20
 R2.7 := R3.20
 R2.6 := R3.19
@@ -5147,7 +5163,7 @@ 
      Logic and bits
      
 
    • sindex (0..15) is the starting bit index in the source register
      • 
 
    
 
-
    +
     lea      R1,$ffff[R0]     ; ffff
 add      R2,R0,R0         ; 0000
 extract  R2,R1,11,3,4     ; 0f00  R2.11-8 := R1.3-0
@@ -5221,7 +5237,7 @@ 
    Logic and bits
    
 Here is another example:
 
    
 
-
    +
     add      R3,R0,R0
 extract  R3,R1,13,5,1     ; 2000
 lea      R4,$ffff[R0]
@@ -5235,9 +5251,9 @@ 
    Logic and bits
    
 
 
 
-
    
-
    Memory
    
-
    
+
    
+
    Memory
    
+
    
 
    
 A memory address is a 16-bit binary number.  Instructions don't
 specify addresses directly; they specify an address with two
@@ -5264,8 +5280,8 @@ 
    Memory
    
 
    
 
 
      
-
    • lea
      
-
      
+
    • lea
      
+
      
 
      
 The load effective address instruction lea Rd,disp[Rx] calculates
 the effective address of the operand disp[Rx] and places the result in
@@ -5275,8 +5291,8 @@ 
      Memory
      
 
      
 
      • 
 
-
    • load
      
-
      
+
    • load
      
+
      
 
      
 The load instruction load Rd,disp[Rx] calculates the effective
 address of the operand disp[Rx] and copies the word in memory at the
@@ -5296,7 +5312,7 @@ 
      Memory
      
 
      
 Examples
 
      
-
      +
       load  R12,count[R0]   ; R12 := count
 load  R6,arrayX[R2]   ; R6 := arrayX[R2]
 load  R3,$2b8e[R5]    ; R3 := mem[2b8e+R5]
@@ -5304,8 +5320,8 @@ 
      Memory
      
 
      
 
      • 
 
-
    • store
      
-
      
+
    • store
      
+
      
 
      
 The store instruction store Rd,disp[Rx] calculates the effective
 address of the operand disp[Rx] and the value of the destination
@@ -5344,7 +5360,7 @@ 
      Memory
      
 Examples
 
      
 
-
      +
       store  R3,$2b8e[R5]
 store  R12,count[R0]
 store  R6,arrayX[R2]
@@ -5352,8 +5368,8 @@ 
      Memory
      
 
      
 
      • 
 
-
    • Stack representation
      
-
      
+
    • Stack representation
      
+
      
 
      
 Three instructions (push, pop, top) support operations on a stack
 represented as an array of contiguous elements, where the stack grows
@@ -5406,14 +5422,14 @@ 
      Memory
      
 
      
 
      • 
 
-
    • push
      
-
      
+
    • push
      
+
      
 
      
 The push instruction pushes an element onto a stack.  It is RRR
 format, and its general form is:
 
      
 
-
      +
       push   Rd,Ra,Rb
 
      
 
@@ -5435,7 +5451,7 @@ 
      Memory
      
 and the stack mask bit is set.  The operational semantics is:
 
      
 
-
      +
       if Ra < Rb
   then Ra := Ra + 1; mem[Ra] := Rd
   else R15.sovfl := 1, req.sovfl := 1
@@ -5458,14 +5474,14 @@ 
      Memory
      
 
      
 
      • 
 
-
    • pop
      
-
      
+
    • pop
      
+
      
 
      
 The push instruction removes an element onto a stack and returns it.
 The instruction is RRR format, and its general form is:
 
      
 
-
      +
       pop    Rd,Ra,Rb
 
      
 
@@ -5488,7 +5504,7 @@ 
      Memory
      
 semantics is:
 
      
 
-
      +
       if Ra >= Rb
   then Rd := mem[Ra]; Ra := Ra - 1
   else R15.suvfl := 1, req.suvfl := 1
@@ -5496,14 +5512,14 @@ 
      Memory
      
 
      
 
      • 
 
-
    • top
      
-
      
+
    • top
      
+
      
 
      
 The top instruction returns the top element on a stack but does not
 remove it.  The instruction is RRR format, and its general form is:
 
      
 
-
      +
       top    Rd,Ra,Rb
 
      
 
@@ -5525,7 +5541,7 @@ 
      Memory
      
 semantics is:
 
      
 
-
      +
       if Ra >= Rb
   then Rd := mem[Ra]
   else R15.suvfl := 1, req.suvfl := 1
@@ -5533,8 +5549,8 @@ 
      Memory
      
 
      
 
      • 
 
-
    • save
      
-
      
+
    • save
      
+
      
 
      
 The save instruction stores a sequence of adjacent registers into a
 block of contiguous memory locations.  The sequence of registers is
@@ -5557,7 +5573,7 @@ 
      Memory
      
 For example, the following save instruction
 
      
 
-
      +
       save R2,R9,20[R14]
 
      
 
@@ -5565,7 +5581,7 @@ 
      Memory
      
 is equivalent to the following sequence of store instructions:
 
      
 
-
      +
       store  R2,20[R14]
 store  R3,21[R14]
 store  R4,22[R14]
@@ -5584,7 +5600,7 @@ 
      Memory
      
 an EXP format instruction:
 
      
 
-
      +
       save Rd,Re,gh[Rf]
 
      
 
@@ -5616,14 +5632,14 @@ 
      Memory
      
 example, 
 
      
 
-
      +
       save    R11,R3,3[R5]
 
      
 
 
      
 is equivalent to
 
      
-
      +
       store   R11,3[R5]
 store   R12,4[R5]
 store   R13,5[R5]
@@ -5637,15 +5653,15 @@ 
      Memory
      
 
      
 
      • 
 
-
    • restore
      
-
      
+
    • restore
      
+
      
 
      
 Restore Rd,disp[Ra] loads R1, …, Rd from consecutive memory
 locations starting from the effective address.
 For example,
 
      
 
-
      +
       restore R5,20[R14]
 
      
 
@@ -5653,7 +5669,7 @@ 
      Memory
      
 is equivalent to
 
      
 
-
      +
       load   R1,20[R14]
 load   R2,21[R14]
 load   R3,22[R14]
@@ -5692,7 +5708,7 @@ 
      Memory
      
 
      
 For example, consider this instruction:
 
      
-
      +
       restore  R3,R10,4[R14]
 
      
 
@@ -5700,7 +5716,7 @@ 
      Memory
      
 The effect is equivalent to
 
      
 
-
      +
       load  R3,4[R14]
 load  R4,5[R14]
 load  R5,6[R14]
@@ -5715,32 +5731,32 @@ 
      Memory
      
 
    
 
    
 
-
    
-
    Flow of control
    
-
    
+
    
+
    Flow of control
    
+
    
 
    
 
      
-
    • jump
      • 
-
    • jumpc0, jumpc1
      • 
-
    • jal
      • 
-
    • jumpz, jumpnz
      • 
+
    • jump
      • 
+
    • jumpc0, jumpc1
      • 
+
    • jal
      • 
+
    • jumpz, jumpnz
      • 
 
    
 
    
 
-
    
-
    System
    
-
    
+
    
+
    System
    
+
    
 
    
 
      
-
    • trap
      • 
-
    • getctl, putctl
      • 
-
    • resume
      • 
+
    • trap
      • 
+
    • getctl, putctl
      • 
+
    • resume
      • 
 
    
 
    
 
    
-
    
-
    Assembly language instruction formats with examples
    
-
    
+
    
+
    Assembly language instruction formats with examples
    
+
    
 
    • 
 
 
 
 
    
 
 
@@ -5836,9 +5852,9 @@ 
    Assembly language instruction formats with examples
    
 
-
    
-
    Instruction set
    
-
    
+
    
+
    Instruction set
    
+
    
 
    
 
 
    
@@ -6594,8 +6610,8 @@ 
    Instruction set
    
 
    
 
 
      
-
    • Pseudoinstructions
      
-
      
+
    • Pseudoinstructions
      
+
      
 
      
 save  
 save     |       RX   | RX    | f,9  | M[ea] := R1, …, M[ea+d-1] := Rd  M[Rb+ofs+(f-e+1)] := Rf |
@@ -6608,11 +6624,11 @@ 
      Instruction set
      
 
      
 
 
-
      
-
      Sigma32 Architecture reference
      
-
      
+
      
+
      Sigma32 architecture
      
+
      
 
      
-(Future extension - no currently available)
+(Future extension - not currently available)
 
      
 
 
      
@@ -6638,9 +6654,9 @@ 
      Sigma32 Architecture reference
      
 
      
 
      
 
-
      
-
      Assembly language reference
      
-
      
+
      
+
      Assembly language reference
      
+
      
 
      
 :CUSTOMID: sec-assembly-language
 
      
@@ -6697,7 +6713,7 @@ 
      Assembly language reference
      
 
      
 Assembly language
 
      
-
      +
       add    R3,R5,R1
 sub    R4,R2,R3
 mul    R1,R9,R10   
@@ -6706,16 +6722,16 @@ 
      Assembly language reference
      
 
      
 Machine language
 
      
-
      +
       0351
 1423
 219a
 
      
 
      
 
-
      
-
      Assembly language statement formats
      
-
      
+
      
+
      Assembly language statement formats
      
+
      
 
      
 Assembly language statements generally correspond to the instruction
 formats, but there is not an exact correspondence for several reasons:
@@ -6889,9 +6905,9 @@ 
      Assembly language statement formats
      
 
      
 
 
-
      
-
      Programs, modules, and files
      
-
      
+
      
+
      Programs, modules, and files
      
+
      
 
      
 The assembler inputs a program in assembly language.  Its primary
 output is an object module which contains the machine language code.
@@ -6926,9 +6942,9 @@ 
      Programs, modules, and files
      
 
      
 
      
 
-
      
-
      Values
      
-
      
+
      
+
      Values
      
+
      
 
      
 A value is a 16-bit word.  An assembly language program uses
 expressions to denote values, but the actual underlying quantity is a
@@ -6951,9 +6967,9 @@ 
      Values
      
 
    
 
    
 
-
    
-
    Expressions
    
-
    
+
    
+
    Expressions
    
+
    
 
    
 An expression is syntax that denotes a value. 
 
    
@@ -7149,9 +7165,9 @@ 
    Expressions
    
 
    
 
    
 
-
    
-
    Location counter
    
-
    
+
    
+
    Location counter
    
+
    
 
    
 The assembler maintains a variable called the location counter, which
 is the address where the next word of object code will be loaded.  The
@@ -7175,9 +7191,9 @@ 
    Location counter
    
 
    
 
    
 
-
    
-
    Attributes
    
-
    
+
    
+
    Attributes
    
+
    
 
    
 A machine language program consists of words stored in memory at
 particular addresses.  A word is just a collection of 16 bits; it has
@@ -7209,9 +7225,9 @@ 
    Attributes
    
 
    
 
    
 
-
    
-
    Code statements
    
-
    
+
    
+
    Code statements
    
+
    
 
    
 Each line of source code is an assembly language statement.  Unlike
 higher level languages, assembly language statements are not nested.
@@ -7262,9 +7278,9 @@ 
    Code statements
    
 
 
    
 
-
    
-
    Instructions
    
-
    
+
    
+
    Instructions
    
+
    
 
    
 
 
    
 
 
@@ -7333,9 +7349,9 @@ 
    Instructions
    
 
 
-
    
-
    data
    
-
    
+
    
+
    data
    
+
    
 
    
 The data statement specifies a sequence of constants to be placed in
 consecutive memory locations starting at the location counter, subject
@@ -7348,7 +7364,7 @@ 
    data
    
 Suppose x1, x2, etc are 4-digit hex constants.  Then
 
    
 
-
    +
     data  x1,x2,x3,x4,x5,x6
 
    
 
@@ -7356,7 +7372,7 @@ 
    data
    
 is equivalent to
 
    
 
-
    +
     data x1,x2,x3
 data x4,x5,x6
 
    
@@ -7386,9 +7402,9 @@ 
    data
    
 
    
 
 
-
    
-
    Directives
    
-
    
+
    
+
    Directives
    
+
    
 
    
 A directive is an assembly language statement that gives further
 information about how to translate the program to object code and how
@@ -7397,9 +7413,9 @@ 
    Directives
    
 
    
 
    
 
-
    
-
    module
    
-
    
+
    
+
    module
    
+
    
 
    
 A program may be organized as a collection of modules, where each
 module appears in a separate file.  When several modules are present,
@@ -7409,7 +7425,7 @@ 
    module
    
 code for module named abc:
 
    
 
-
    +
     abc   module 
 
    
 
@@ -7443,10 +7459,10 @@ 
    module
    
 
    
 
    
 
-
    
-
    equ
    
-
    
-
    +
    
+
    equ
    
+
    
+
     codeWrite  equ  2
 codeRead   equ  1
 
    
@@ -7455,7 +7471,7 @@ 
    equ
    
 The expression in an equ can calculate the size of an object:
 
    
 
-
    +
     astart     data 5
            data 9
            data 78
@@ -7465,10 +7481,10 @@ 
    equ
    
 
    
 
    
 
-
    
-
    block
    
-
    
-
    +
    
+
    block
    
+
    
+
     asize   equ    100
 n       data   asize
 arr     block  asize
@@ -7476,9 +7492,9 @@ 
    block
    
 
    
 
    
 
-
    
-
    org
    
-
    
+
    
+
    org
    
+
    
 
    
 The org statement sets the location counter to a specified address.
 Subsequent instructions and data will be placed in memory at
@@ -7510,9 +7526,9 @@ 
    org
    
 
    
 
    
 
-
    
-
    import
    
-
    
+
    
+
    import
    
+
    
 
    
 The import statement states that the value of an identifier is defined
 in another module.  During the assembly of the module containing the
@@ -7520,7 +7536,7 @@ 
    import
    
 will be replaced by the actual value by the linker.  For example,
 
    
 
-
    +
     x   import  Mod1,x
 y   import  Mod1,abc
 
    
@@ -7533,9 +7549,9 @@ 
    import
    
 
    
 
    
 
-
    
-
    export
    
-
    
+
    
+
    export
    
+
    
 
    
 An export statement says that the module is making the value of a
 symbol available for use in other modules, which may import it.  The
@@ -7546,7 +7562,7 @@ 
    export
    
 Examples:
 
    
 
-
    +
     export  haltcode,0
 export  fcn,002c
 
    
@@ -7558,7 +7574,7 @@ 
    export
    
 it:
 
    
 
-
    +
     Mod1     module
          export fcn
 
@@ -7593,9 +7609,9 @@ 
    export
    
 
    
 
    
 
-
    
-
    Summary of assembly language statements
    
-
    
+
    
+
    Summary of assembly language statements
    
+
    
 
    
 
    
 
 
@@ -7659,13 +7675,13 @@ 
    Summary of assembly language statements
    
 
 
 
-
    
-
    User interface
    
-
    
+
    
+
    User interface
    
+
    
 
    
-
    
-
    Files and modules
    
-
    
+
    
+
    Files and modules
    
+
    
 
      
 
    • In Modules tab, click Choose Files
 
        
@@ -7677,9 +7693,9 @@ 
        Files and modules
        
 
      
 
    
 
    
-
    
-
    Simple standalone programs
    
-
    
+
    
+
    Simple standalone programs
    
+
    
 
    
 If a program does not import any names, it is standalone.  The text
 of the program is shown in the editor pane.  Go to the Assembler pane
@@ -7691,9 +7707,9 @@ 
    Simple standalone programs
    
 
    
 
    
 
-
    
-
    Programs with multiple modules
    
-
    
+
    
+
    Programs with multiple modules
    
+
    
 
    
 A module consists of program text, and it may have an optional file,
 and an optional module name.
@@ -7819,9 +7835,9 @@ 
    Linker
    
 
    
 
    
 
-
    
-
    Object language
    
-
    
+
    
+
    Object language
    
+
    
 
    
 Object code is expressed in a textual language, so the object code
 readable to a human (at least, for a human who understands machine
@@ -7856,20 +7872,20 @@ 
    Object language
    
 
    
 
    
 
-
    
-
    Statement syntax
    
+
    
+
    Statement syntax
    
 
    
-
    
-
    module
    
+
    
+
    module
    
 
    
 
-
    
-
    org
    
+
    
+
    org
    
 
    
 
-
    
-
    data
    
-
    
+
    
+
    data
    
+
    
 
    
 data x0,x1,…,xj-1
 
    
@@ -7879,21 +7895,21 @@ 
    data
    
 location counter.  For each word x, the linker performs:
 
    
 
-
    +
     mem[llc] := x
 llc := llc + 1
 
    
 
    
 
    
 
-
    
-
    import
    
-
    
+
    
+
    import
    
+
    
 
    
 General form
 
    
 
-
    +
     import  modName,externalName,address,field
 
    
 
@@ -7901,21 +7917,21 @@ 
    import
    
 Examples
 
    
 
-
    +
     import  Mod2,abc,03c4,dist
 import  Mod3,ybit,03be,g
 
    
 
    
 
    
 
-
    
-
    export
    
+
    
+
    export
    
 
    
 
 
-
    
-
    relocate
    
-
    
+
    
+
    relocate
    
+
    
 
    
 The relocate statement specifies a list of addresses of words that
 must be relocated.  Suppose the value x is specified in a relocate
@@ -7923,7 +7939,7 @@ 
    relocate
    
 the linker will set mem[x+y] = obj[x]+y.
 
    
 
-
    +
     relocate hex4,hex4,...
 
    
 
@@ -7943,7 +7959,7 @@ 
    relocate
    
 code[addr] := code[addr] + llc
 
    
 
-
    +
     relocate  addr,addr,...,addr
 
    
 
@@ -7954,9 +7970,9 @@ 
    relocate
    
 
    
 
    
 
-
    
-
    Module metadata
    
-
    
+
    
+
    Module metadata
    
+
    
 
    
 The assembler and linker create metadata files which enable the
 emulator to show the assembly language statement corresponding to the
@@ -8033,7 +8049,7 @@ 
    Module metadata
    
 Here is an example of a metadata file:
 
    
 
-
    +
     fasmap 17
 14,14,15,15,16,16,17,17,18,19
 19,20,20,21,21,22,24
@@ -8046,9 +8062,9 @@ 
    Module metadata
    
 
    
 
    
 
-
    
-
    Linker
    
-
    
+
    
+
    Linker
    
+
    
 
      
 
    • GUI: selected module is main program and also receives the
 executable.  All other modules are linked, and their object code is
@@ -8061,13 +8077,13 @@ 
      Linker
      
 
    
 
    
 
-
    
-
    Loader
    
-
    
+
    
+
    Loader
    
+
    
 
    
-
    
-
    Executable code
    
-
    
+
    
+
    Executable code
    
+
    
 
    
 An executable module is written in the same language as object
 modules.  The only difference is that an executable module must
@@ -8100,15 +8116,15 @@ 
    Programming
    
 
    
 
    
 
-
    
-
    Structure of a program
    
-
    
+
    
+
    Structure of a program
    
+
    
 
    
 Simple ("static") variabls need to be declared with a data statement,
 which also gives an initial value.
 
    
 
-
    +
     x  data  23
 
    
 
@@ -8120,13 +8136,13 @@ 
    Structure of a program
    
 
    
 
    
 
-
    
-
    How to perform commmon tasks
    
-
    
+
    
+
    How to perform commmon tasks
    
+
    
 
    
-
    
-
    Using extract
    
-
    
+
    
+
    Using extract
    
+
    
 
    
 A special case is to move a Boolean from one place to another.
 
    
@@ -8193,7 +8209,7 @@ 
    Using extract
    
 Example:
 
    
 
-
    +
     field   R3,4,  ; R3 := 0fc0
 
    
 
@@ -8209,16 +8225,16 @@ 
    Using extract
    
 
    
 
    
 
-
    
-
    Copying one register to another
    
-
    
+
    
+
    Copying one register to another
    
+
    
 
    
 Sometimes you want to copy a value from one register to another: R3 :=
 R12.  There isn't an instruction specifically for this purpose,
 because there is no need: just use the add instruction:
 
    
 
-
    +
     add R3,R12,R0 ; R3 := R12
 
    
 
@@ -8232,9 +8248,9 @@ 
    Copying one register to another
    
 
    
 
    
 
-
    
-
    Compilation
    
-
    
+
    
+
    Compilation
    
+
    
 
    
 There are two ways to handle variables:
 
    
@@ -8259,7 +8275,7 @@ 
    Compilation
    
 language, using each style:
 
    
 
-
    +
     x = 50;
 y = 2*z;
 x = x+1+z;
@@ -8269,7 +8285,7 @@ 
    Compilation
    
 Statement-by-statement style
 
    
 
-
    +
     ; x = 50;
      lea    R1,$0032   ; R1 = 50
      store  R1,x[R0]   ; x = 50
@@ -8293,7 +8309,7 @@ 
    Compilation
    
 Register-variable style
 
    
 
-
    +
     ; Usage of registers
 ;   R1 = x
 ;   R2 = y
@@ -8347,19 +8363,19 @@ 
    Compilation
    
 
    
 
    
 
-
    
-
    Errors: avoiding, finding, and fixing
    
-
    
+
    
+
    Errors: avoiding, finding, and fixing
    
+
    
 
    
-
    
-
    Critical regions
    
-
    
+
    
+
    Critical regions
    
+
    
 
    
 A testset instruction is not semantically equivalent to a load
 followed by a store.  Consider this example:
 
    
 
-
    +
     ; (1) testset
      testset   R1,mutex[R0]
 
    
@@ -8368,7 +8384,7 @@ 
    Critical regions
    
 It is not the same as
 
    
 
-
    +
     ; (2) sequence of instructions
      load     R1,mutex[R0]
      lea      R2,1[R0]
@@ -8397,9 +8413,9 @@ 
    Critical regions
    
 
    
 
    
 
-
    
-
    Robust programming
    
-
    
+
    
+
    Robust programming
    
+
    
 
    
 *Use a systematic programming process
 
    
@@ -8439,13 +8455,13 @@ 
    Robust programming
    
 
    
 
    
 
-
    
-
    Error messages
    
+
    
+
    Error messages
    
 
    
 
-
    
-
    Runtime debugging
    
-
    
+
    
+
    Runtime debugging
    
+
    
 
    
 What if an instruction doesn't do what you expected?
 
    
@@ -8472,9 +8488,9 @@ 
    Runtime debugging
    
 
    
 
    
 
-
    
-
    Breakpoints
    
-
    
+
    
+
    Breakpoints
    
+
    
 
    
 (Note: the breakpoint system is not fully implemented yet; the
 following describes a temporary breakpoint facility.)
@@ -8520,9 +8536,9 @@ 
    Breakpoints
    
 
    
 
    
 
-
    
-
    Installation
    
-
    
+
    
+
    Installation
    
+
    
 
    
 You can run most of Sigma16 in a web browser – there's nothing to
 download, nothing to install.  Visit the [Sigma16 home
@@ -8533,9 +8549,9 @@ 
    Installation
    
 
    
 
    
 
-
    
-
    Command line tools
    
-
    
+
    
+
    Command line tools
    
+
    
 
    
 Sigma16 also contains some advanced features that use the command
 line in a shell.  These features include text commands for
@@ -8548,13 +8564,13 @@ 
    Command line tools
    
 
    
 
    
 
-
    
-
    node and npm
    
+
    
+
    node and npm
    
 
    
 
-
    
-
    Configuring the shell
    
-
    
+
    
+
    Configuring the shell
    
+
    
 
    
 Shell running bash
 
    
@@ -8565,7 +8581,7 @@ 
    Configuring the shell
    
 location.  In a bash shell running on cygwin, try /Users/yourlogin.
 
    
 
-
    +
     SIGMA16=/Users/yourlogin/Documents/path/to/SigmaProject/Sigma16
 export SIGMA16
 alias helloworld="node ${SIGMA16}/app/helloworld.js"
@@ -8573,19 +8589,19 @@ 
    Configuring the shell
    
 
    
 
    
 
-
    
-
    Testing the installation
    
-
    
-
    +
    
+
    Testing the installation
    
+
    
+
     $ node --version
 v16.5.0
 
    
 
    
 
    
 
-
    
-
    Building Sigma16
    
-
    
+
    
+
    Building Sigma16
    
+
    
 
    
 The Web version of Sigma16 contains several files that need to be
 built from source.  Of course, if you launch the app from the Sigma16
@@ -8597,11 +8613,11 @@ 
    Building Sigma16
    
 Use emacs to build *.html from source *.org
 
    
 
-
    +
     ^C ^E h h
 
    
 
-
    +
     $ npm install -g wabt
 $ wat2wasm emcore.wat --enable-threads
 
    
@@ -8615,9 +8631,9 @@ 
    About Sigma16
    
 
    
 
    
 
-
    
-
    Copyright and license
    
-
    
+
    
+
    Copyright and license
    
+
    
 
    
 The architecture, software tools, and documentation were designed,
 implemented, and written by John O'Donnell.  Contact email:
@@ -8647,9 +8663,9 @@ 
    Copyright and license
    
 
    
 
    
 
-
    
-
    In case of problems
    
-
    
+
    
+
    In case of problems
    
+
    
 
    
 If you encounter a problem with the app, please file a bug report.  It
 is essential in a bug report (for any software, not just Sigma16) to
@@ -8677,13 +8693,13 @@ 
    In case of problems
    
 
    
 
    
 
-
    
-
    Release notes
    
-
    
+
    
+
    Release notes
    
+
    
 
    
-
    
-
    Version 3.4.0
    
-
    
+
    
+
    Version 3.4.0
    
+
    
 
      
 
    • Bit indexing is changed to "little end" style.  The least
 significant bit has index 0, and the most significant bit has
@@ -8696,9 +8712,9 @@ 
      Version 3.4.0
      
 
    
 
    
 
    
-
    
-
    Version 3.3.2, April 2021
    
-
    
+
    
+
    Version 3.3.2, April 2021
    
+
    
 
      
 
    • There is no change in the architecture
      • 
 
    • The software is modified to enable it to continue working when a
@@ -8708,12 +8724,12 @@ 
      Version 3.3.2, April 2021
      
 
    
 
    
 
    
-
    
-
    Version 3.2.3, development from April 2021
    
+
    
+
    Version 3.2.3, development from April 2021
    
 
    
-
    
-
    Version 3.2.2, March 2021
    
-
    
+
    
+
    Version 3.2.2, March 2021
    
+
    
 
      
 
    • A bug in breakpoints is fixed
      • 
 
    • In addition, there is a new way to specify breakpoings using trap
      • 
@@ -8723,9 +8739,9 @@ 
      Version 3.2.2, March 2021
      
 
    
 
    
 
-
    
-
    Version 3.2.1, February 2021
    
-
    
+
    
+
    Version 3.2.1, February 2021
    
+
    
 
    
 Version 3.2 brings several changes that will be visible to users of
 previous versions of Sigma16:
@@ -8742,7 +8758,7 @@ 
    Version 3.2.1, February 2021
    
 the conditional jumps.)  Here's an example:
 
 
-
    +
     ; Old style -- these instructions have been removed
      cmplt   R1,R2,R3      ; R1 := R2 < R3
      jumpt   R1,loop[R0]   ; if R2 < R3 then goto loop
@@ -8826,9 +8842,9 @@ 
    Version 3.2.1, February 2021
    
 
    
 
 
-
    
-
    Text of GPL3 License
    
-
    
+
    
+
    Text of GPL3 License
    
+
    
 
    
 GNU GENERAL PUBLIC LICENSE
 Version 3, 29 June 2007
@@ -9262,7 +9278,7 @@ 
    Text of GPL3 License
    
 
    
 
    
 
    Author: John T. O'Donnell
    
-
    Created: 2021-12-20 Mon 15:49
    
+
    Created: 2022-01-13 Thu 11:15
    
 
    Validate
    
 
    
 
diff --git a/docs/UserGuide/Sigma16UserGuide.org b/docs/UserGuide/Sigma16UserGuide.org
index 83372b0..75a233a 100644
--- a/docs/UserGuide/Sigma16UserGuide.org
+++ b/docs/UserGuide/Sigma16UserGuide.org
@@ -38,10 +38,7 @@
 
 Sigma16 is a computer architecture designed for research and
 teaching in computer systems.  The architecture is simple yet
-powerful.  It is organized into subsets to make it easier to use:
-the core subset is suitable for beginners, the standard subset
-offers flexible programming techniques, and the full system supports
-the study of systems programming.
+powerful.
 
 This application provides a complete environment for experimenting
 with the architecture.  It includes an editor, assembler, linker,
@@ -58,23 +55,35 @@ the Installation section.  There is also a digital circuit
 these tools, machine language programs can run on both the emulator
 and the circuit.
 
-For a quick start, begin with the tutorials, which introduce the
-architecture step by step.  The tutorials explain the machine, show
-how to program it, and demonstrate how to enter and run a program
-and how to use the programming environment.
-
-The remainder of the user guide is organised by topic, with chapters
-on the architecture, the assembly language, the linker, and
-programming techniques.
-
-* Tutorials
+The architecture is organized into subsets to make it easier to use:
+- The *Core* subset contains a small and simple instruction set which
+  is a good starting point for learning about computer architecture.
+  Although it is simple, Core is powerful enough to support realistic
+  programming.
+- The *Standard* subset offers flexible programming techniques,
+  including manipulation of bits and fields, arithmetic on natural
+  numbers and arbitrary precision integers, and concise support for
+  stack frames.
+- The full *System* supports the study of systems programming.  It
+  supports interrupts, concurrent processes, and mutual exclusion.
+Core is a subset of Standard, which is a subset of System.  To learn
+the full architecture, start with Core and then go on to Standard and
+System.
+
+For a quick start, begin with the Core architecture tutorials, which
+introduce the architecture step by step.  The tutorials explain the
+machine, show how to program it, and demonstrate how to enter and run
+a program and how to use the programming environment.  A reference
+section follows the tutorials.
+
+* Core architecture
 
 The following short tutorials introduce the system; full details
 appear in later sections.  You can keep the tutorials visible in the
 right panel while following along with the exercises in the main
 panel.
 
-** Core architecture tutorial
+** Core architecture tutorials
 :PROPERTIES:
 :CUSTOM_ID: sec-core-tutorial
 :END:
@@ -1562,7 +1571,6 @@ commercial computers that achieve success in the marketplace
 eventually become encrusted with complications that help support
 backward compatibility; this can lead to great complexity.
 
-*** Testing and debugging
 *** Breakpoints
 
 Quick summary, explanation follows.  There are two ways to set a
@@ -1609,7 +1617,7 @@ to modify the program or reassemble it, or if you realise that you
 want a breakpoint after execution has already started, then an
 external break is better.
 
-**** Trap break
+*** Trap break
 
 You can use a trap instruction to break execution when it executes.
 The first operand of the instruction is a register that must contain
@@ -1651,7 +1659,7 @@ to resume full speed execution.
 For an example of a long running program with a trap break, see
 Examples / Testing / Looper.
 
-**** External break
+*** External break
 
 You can also tell the user interface to perform a breakpoint without
 modifying the program.  You need to know the address of the
@@ -1677,7 +1685,7 @@ that location is encountered.  To prevent this, open the breakpoint
 popup again and click Disable.
 
 
-*** Summary of Core Architecture
+** Summary of Core Architecture
 
 The following table summarises the instructions in the Core subset of
 Sigma16.  This is an extract from the table for the full architecture
@@ -1719,18 +1727,22 @@ Assembly directives
 
 - data
 
-** Standard architecture tutorial
-*** Logic
-*** Bit fields and shifting
-*** Stack instructions
-*** Saving registers for procedure call
+* Standard architecture
+
+* Standard architecture tutorials
+** Logic
+** Bit fields and shifting
+** Stack instructions
+** Saving registers for procedure call
 
+** Arithmetic on natural numbers
 
-*** Arithmetic on natural numbers
-** Systems architecture tutorial
+* Systems architecture
+
+** Systems architecture tutorials
 *** System control registers
 *** Interrupt handlers
-** S32 architecture tutorial
+
 
 * Sigma16 Architecture reference
 :PROPERTIES:
@@ -3462,9 +3474,9 @@ Instructions marked x are not are not implemented in this version.
  restore  |   | RX   | RX    | f,a  | R1 := M[ea], ..., Rd := M[ea+d-1] |
 
 
-* Sigma32 Architecture reference
+* Sigma32 architecture
 
-(Future extension - no currently available)
+(Future extension - not currently available)
 
 Sigma16 consists of a 16-bit architecture (S16) and a 32 bit extended
 architecture (S32).  This section discusses 
diff --git a/docs/welcome/welcome.html b/docs/welcome/welcome.html
index b43d9d4..b92c477 100644
--- a/docs/welcome/welcome.html
+++ b/docs/welcome/welcome.html
@@ -3,7 +3,7 @@
 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
 
 
-
+
 
 
 ‎
@@ -220,11 +220,11 @@
 
    
 
    Sigma16
    
 
-Version 3.4.1, November 2021.
+Version 3.4.1, January 2022.
 
-
    
-
    Overview
    
-
    
+
    
+
    Overview
    
+
    
 
    
 Sigma16 is a computer architecture designed for research and teaching
 in computer systems.  This application provides a complete environment
@@ -243,9 +243,9 @@ 
    Overview
    
 
    
 
    
 
-
    
-
    Getting started
    
-
    
+
    
+
    Getting started
    
+
    
 
    
 The User Guide begins with a set of tutorials that introduce the
 system.  The best place to start is with the Hello, World! tutorial.
@@ -261,9 +261,9 @@ 
    Getting started
    
 
    
 
    
 
-
    
-
    Updates and further information
    
-
    
+
    
+
    Updates and further information
    
+
    
 The Sigma16 Home Page contains a link to run the
 latest version as well as up-to-date information on the system.  It's
@@ -277,9 +277,9 @@ 
    Updates and further information
    
 
    
 
    
 
-
    
-
    License
    
-
    
+
    
+
    License
    
+
    
 
    
 License: GNU GPL Version 3 or later.
 
    
@@ -306,7 +306,7 @@ 
    License
    
 
    
 
    
 
    
-
    Created: 2021-11-14 Sun 15:35
    
+
    Created: 2022-01-10 Mon 20:22
    
 
    Validate
    
 
    
 
diff --git a/src/base/assembler.mjs b/src/base/assembler.mjs
index 9e0f380..3f95ba6 100644
--- a/src/base/assembler.mjs
+++ b/src/base/assembler.mjs
@@ -43,7 +43,7 @@ export class AsmInfo {
 	this.modName = "anonymous";     // defined in optional module statement
         this.text = "";                 // raw source text
         this.asmSrcLines = [];          // list of lines of source text
-	this.asmStmt = [];              // statements correspond to lines of source
+	this.asmStmt = [];              // statements correspond to source lines
 	this.symbols = [];              // symbols used in the source
 	this.symbolTable = new Map ();  // symbol table
 	this.locationCounter = 0;       //  next code address
@@ -539,10 +539,10 @@ comments field
    contains any characters
 */
 
-const identParser = /^[a-zA-Z][a-zA-Z0-9_]*$/;
-const nameParser = /^[a-zA-Z][a-zA-Z0-9_]*$/;
-const intParser = /^-?[0-9]+$/;
-export const hexParser = /^\$([0-9a-f]{4})$/;
+const identParser = /^[a-zA-Z][a-zA-Z0-9_]*$/
+const nameParser =  /^[a-zA-Z][a-zA-Z0-9_]*$/
+const intParser =   /^-?[0-9]+$/
+export const hexParser = /^\$([0-9a-f]{4})$/
 
 const rcParser =
     /^R([0-9a-f]|(?:1[0-5])),([a-zA-Z][a-zA-Z0-9]*)$/;
@@ -623,9 +623,7 @@ const parseSplitFields = new RegExp(regexpSplitFields);
 // const xParser = /^([-a-zA-Z0-9_\$]+)\[(R|r)([0-9a-f]|(?:1[0-5]))\]/;
 
 
-
 function requireX (ma, s, field) {
-    console.log (`requireX <${field}>`)
     const xrParser = /^([^\[]+)\[(.*)\]$/
     let disp = "0"
     let index = 0
@@ -635,6 +633,9 @@ function requireX (ma, s, field) {
         const regsrc = xr[2]
         index = requireReg (ma, s, regsrc)  // disp = field
         console.log (`requireX parse failed`)
+    } else { // allow [R0] to be omitted
+        disp = field
+        index = 0
     }
     const result = {disp, index}
     console.log (`requireX field=${field} disp=<${disp}> index=${index}`)
@@ -684,6 +685,14 @@ function requireNoperands (ma, s, n) {
 
 // k4 is always fixed, never relocatable
 
+function requireK16 (ma, s, field, xs) {
+    com.mode.devlog (`requireK4 <${xs}>`);
+    const a = s.address.word;
+    const v = evaluate (ma, s, a, xs);
+    const result = v.word;
+    return result;
+}
+
 function requireK4 (ma, s, field, xs) {
     com.mode.devlog (`requireK4 <${xs}>`);
     const a = s.address.word;
diff --git a/src/server/sigserver.mjs b/src/server/sigserver.mjs
index a55aa4a..7c6d193 100644
--- a/src/server/sigserver.mjs
+++ b/src/server/sigserver.mjs
@@ -155,7 +155,22 @@ express.static.mime.define({'text/html': ['html']});
 
 app.get ('/', (req,res) => {
     console.log (`responding-/`)
-    res.sendFile (path.join (S16_BUILD_DIR, 'index.html'))
+    res.sendFile (path.join ('/app', 'topindex.html'))
+})
+
+app.get ('/index.html', (req,res) => {
+    console.log (`responding-/-index.html`)
+    res.sendFile (path.join ('/app', 'topindex.html'))
+})
+
+app.get ('/default.html', (req,res) => {
+    console.log (`responding-/-default.html`)
+    res.sendFile (path.join ('/app', 'topindex.html'))
+})
+
+app.get ('/docstyle.css', (req,res) => {
+    console.log (`responding-/`)
+    res.sendFile (path.join ('/app', 'docstyle.css'))
 })
 
 //-----------------------------------------------------------------------