This short post describes TRAP 116 and the BASIC RUN, STOP, END and RANDOMIZE commands. For context and a list of other posts on this...

This post describes the BASIC FOR and NEXT loop commands. For context and a list of other posts on this topic, see the PDP-11 BASIC...

This post describes the BASIC READ, INPUT and RESTORE commands. For context and a list of other posts on this topic, see the PDP-11 BASIC...

This post describes the BASIC IF command. For context and a list of other posts on this topic, see the PDP-11 BASIC reverse engineering...

This post will describe the operation of TRAP 124 and the BASIC DIM and LET commands. For completeness, I'll also describe the DATA and...

In this post we'll look at the expression evaluation code. Expressions are used all over the place and the main entry point to parsing...

This post will describe the operation of a few TRAPs that are used to support the functionality that will be analysed in the next posts....

In this post I'll describe user-defined functions and the BASIC DEF command, starting with some TRAPs that support its operation (TRAP...

This post will describe the operation of the ASCII-to-floating point conversion code, TRAP 6. You will need to have read Part 14, Part...

This post will take a look at some more floating point manipulation TRAPs; TRAP 26 (floating point division) and TRAP 34 (floating point...

This post is about multiplication. There are three different multiplication TRAPs found in the PDP-11 BASIC code, with a different one...

This post will examine some of the floating point operations. We'll be looking at TRAP 24 (negate a floating point number), TRAP 20 (add...

In this post I'm going to start the analysis of the floating point number code. I will be looking at the PDP-11 BASIC representation of...

Update 1st March 2021: This post has been updated to reflect refined understanding of TRAP 64 arising from analysis of the floating point...

In this post I'll describe some of the BASIC commands that use runtime state storage, including GOSUB, GOTO and RETURN. For context and a...

This posts begins the analysis of the BASIC program's runtime state management. I'll start with a quick introduction to how the runtime...

In this post I'll be looking at how the SAVE, OLD and DELETE BASIC commands work. For context and a list of other posts on this topic,...

In this post I'll be looking at how the BASIC LIST command works. For context and a list of other posts on this topic, see the PDP-11...

In Part 6 I analysed the code that: Determined whether the user has pressed return, in which case control returns to the beginning of the...

The purpose of this post is to lay the groundwork required to complete the analysis of the main syntax parsing loop. There are a few...