- #SWEET16 WOZNIAK GENERATOR#
- #SWEET16 WOZNIAK UPDATE#
- #SWEET16 WOZNIAK PATCH#
- #SWEET16 WOZNIAK WINDOWS#
#SWEET16 WOZNIAK GENERATOR#
When the code generator needed to access a variable, it didn’t do so directly.
#SWEET16 WOZNIAK UPDATE#
Your program has 100 variables? Then that’s 100 passes through the object code to update references to 100 variables.
#SWEET16 WOZNIAK WINDOWS#
Pass 2 made a pass through the object code once for each variable, since the references to a variable were threaded through the object code as a linked list, similar to how 16-bit Windows threaded external references through the code instead of keeping a separate fixup table.
#SWEET16 WOZNIAK PATCH#
Pass 2 was I/O-bound not only because of the need to patch the object code, but also because the table of line numbers was itself written to disk, there not being enough RAM to keep it in memory.
Even though Pass 1 had all the smarts and Pass 2 was just doing clerical work, it was Pass 2 that took the most time because it was I/O-bound, and floppy disks are not speed demons when it comes to random access. Pass 2 consisted of resolving these references and patching up the code. This performed code generation and left placeholders for references to other locations like branch targets or variables. If you dig through the TASC manual, you can find all sorts of wonderful implementation details.Īll of the real work happened in pass 1. Yet somehow, he finished TASC, and it shipped. He had a sprawling compiler, with no comments, and unhelpful variable names.²
Upon returning to Microsoft, he found that he no longer understood the code. Such is the desperation of developing on a system with very tight memory constraints.Įverything was working smoothly, until the author returned to school for a semester. There was no way to bootstrap it from the interpreter.Īs the author added features, he kept hitting the Apple ][‘s 48KB RAM limit and was forced to delete all the comments from the code, and when that wasn’t enough, he resorted to shortening all the important variable names to one character. This meant that once TASC development reached the point that it required chaining, it could be run only in its compiled form. It was one of a handful of language extension provided by TASC itself, through the use of magic comments that begin with an exclamation point. Chaining was a common technique when your program got too large to fit into memory all at once, so you broke it into multiple programs that each handed off control to each other.Įven if you hadn’t made it that deep into the manual, you could have figured out that TASC was used to compile itself because TASC used its own runtime library.Ĭhaining was not a feature native to Applesoft BASIC. All three passes were written largely in Applesoft, and TASC was used to compile itself.Ĭhaining refers to a program instructing the system to replace the current program in memory with another program, but preserve the values of some or all variables. PASS0 and PASS1 chain to PASS1 and PASS2, respectively. PASS0 simply picks up user inputs and sets up compilation parameters, so it is not really part of the actual compilation process. TASC is a “two-pass” compiler, since it compiles in two major steps. Microsoft licensed the product and hired the author, who spent the summer at the Northup building¹ polishing the code. TASC was written by one person in his dorm room while studying at MIT. That compiler went by the name TASC: The Apple soft Compiler. Back in the early 1980’s, the Apple ][ computer was taking the personal computing world by storm, and Microsoft released a compiler for Applesoft BASIC.
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