6 ms·

Coding a new BASIC interpreter in 2025 to replace a slow one

87 points by nanochess 1y ago

codazoda 1y ago
I applied for a job about 12 years ago where the company was still using BASIC for some of their software. If I remember correctly it was numbered BASIC, not the more modern stuff. I think the software was doing some type of accounting—stuff that worked and they didn't want to change.
- dajtxx 1y ago
  I had a job in the early 90s where another team were using Wang 2200s which I'm sure were coded with line-numbered BASIC. Could be one of those with the everlasting ERP type software running on an emulator.
- user3939382 1y ago
  Wish I could have found that 35 years ago.
Joker_vD 1y ago
> I discovered the pointer to the next line wasn't a good idea, because it needed to move every pointer after a line insertion. Huh? Don't you need to only change the "next-line-pointer" for the line that's right before the inserted line? > but the NEXT changed the line, but on the next statement it would lost track and get back to the line following the NEXT. The loops also require their own stack, but including the counter variable address, a pointer to the TO expression, and a pointer to the STEP expression (5 words in total). Mmm. IIRC, usually the compiled NEXT statement would store the pointer to the corresponding FOR statement, so you don't need an additional stack for loop depth during the execution. But you still need it (or some other sort of chaining) during the program input so whatever. > Typing the program was difficult, as the keyboard bounced a lot. This happens when you read too fast the keyboard, so fast you can see that effectively the key contact isn't perfect. Yeah... I've read that keyboard microcontrollers has to deal with contact bounce even today.
- II2II 1y ago
  > I discovered the pointer to the next line wasn't a good idea, because it needed to move every pointer after a line insertion. I get the impression that they were storing everything sequentially in memory, rather than having a linked list of instructions. Why? I can only speculate. Perhaps it is to make memory management simpler (don't have to keep track of which addresses are in use), or to avoid memory fragmentation in system with limited memory (any modification of code would introduce unusable holes). If that's the case, what you want is an offset rather than an absolute address.
  - Someone 1y ago
    > I get the impression that they were storing everything sequentially in memory, rather than having a linked list of instructions. Why? I can only speculate. I expect that’s because that is how ‘every’ homecomputer basic did it. Yes, that makes it slow to insert or remove a line close to the start of a long program, but it allow those offsets to be 8 bits, gaining a precious byte over a 16-bit absolute address. Now, why they initially chose to waste those bytes? I wouldn’t know, but I guess that, because (FTA) “The CP1610 processor cannot address directly the internal memory in byte terms, instead everything is handled by full word”, they didn’t think of using a single byte.
- Someone 1y ago
  > Mmm. IIRC, usually the compiled NEXT statement would store the pointer to the corresponding FOR statement, so you don't need an additional stack for loop depth during the execution I think you do. Apart from common sense, nothing forbids one from writing stuff like 100 for i = 1 to 10 110 if i = 4 gosub 100 120 print i 130 next 140 return I think many basics also allowed changing that goto 100 to goto 200 and adding 200 for j = 1 to 4 210 print i 220 print j 230 next Yes, things would likely end badly, but the basic interpreter would not be smart enough to reject such programs. Its editor didn’t even guarantee that a for statement had a corresponding next or vice versa; all it guaranteed was that the program consisted of a list of lines that each in isolation are valid basic code.
  - 1y ago
analog8374 1y ago
I love basic Can you OOPize it?
- zanderwohl 1y ago
  Yes, meet Visual Basic 6. It has many OO features stapled on.
  - pasc1878 1y ago
    Or VB.Net for more OOP
  - turtleyacht 1y ago
    Classic ASP (Active Server Pages), and take it to the web.
- andsoitis 1y ago
  The following BASIC implementations support OOP: - Visual Basic .NET - PureBasic - XoJo - FreeBASIC - Gambas - PowerBASIC You can peruse various implementations, IDEs, and tutorials here: https://github.com/JohnBlood/awesome-basic https://github.com/JohnBlood/awesome-basic
____tom____ 1y ago
For those interested in BASIC, here's "A curated list of awesome BASIC dialects, IDEs, and tutorials": https://github.com/JohnBlood/awesome-basic?tab=readme-ov-file https://github.com/JohnBlood/awesome-basic?tab=readme-ov-fil... It's not as popular as Python, obviously, but that lists over fifty implementations of BASIC.
bluedino 1y ago
I always wondered if any engineers suggested changes to make some BASICs faster and the companies didn't want it competing with "real" software
3036e4 1y ago
There is a chapter in the Blue Book about how the GW-BASIC byte code is structured, and from what I understand it used pointers to lines, not just offsets? But I did not look too carefully (guess the answer is in the source code: https://gitlab.com/tkchia/GW-BASIC https://gitlab.com/tkchia/GW-BASIC). That book is full of interesting facts and fun low-level tricks for (GW-)BASIC programming. Available for download here: https://github.com/robhagemans/hoard-of-gwbasic https://github.com/robhagemans/hoard-of-gwbasic Before reading that I never considered how primitive early BASICs were. There is a lot of linear-searching for things (variables, line-numbers) that has to be considered when optimizing.
wkjagt 1y ago
Oscar Toledo (nanochess) is one of my personal heros. And one of his books, Boot Sector Games, is one of my favorite books. Seeing him post something like he just did gives me a kind of joy that is becoming pretty rare on the internet these days, for me at least.

87 points by nanochess 1y ago

I applied for a job about 12 years ago where the company was still using BASIC for some of their software. If I remember correctly it was numbered BASIC, not the more modern stuff. I think the software was doing some type of accounting—stuff that worked and they didn't want to change.

dajtxx 1y ago
I had a job in the early 90s where another team were using Wang 2200s which I'm sure were coded with line-numbered BASIC. Could be one of those with the everlasting ERP type software running on an emulator.
user3939382 1y ago
Wish I could have found that 35 years ago.

Joker_vD 1y ago

> I discovered the pointer to the next line wasn't a good idea, because it needed to move every pointer after a line insertion. Huh? Don't you need to only change the "next-line-pointer" for the line that's right before the inserted line? > but the NEXT changed the line, but on the next statement it would lost track and get back to the line following the NEXT. The loops also require their own stack, but including the counter variable address, a pointer to the TO expression, and a pointer to the STEP expression (5 words in total). Mmm. IIRC, usually the compiled NEXT statement would store the pointer to the corresponding FOR statement, so you don't need an additional stack for loop depth during the execution. But you still need it (or some other sort of chaining) during the program input so whatever. > Typing the program was difficult, as the keyboard bounced a lot. This happens when you read too fast the keyboard, so fast you can see that effectively the key contact isn't perfect. Yeah... I've read that keyboard microcontrollers has to deal with contact bounce even today.

II2II 1y ago
> I discovered the pointer to the next line wasn't a good idea, because it needed to move every pointer after a line insertion. I get the impression that they were storing everything sequentially in memory, rather than having a linked list of instructions. Why? I can only speculate. Perhaps it is to make memory management simpler (don't have to keep track of which addresses are in use), or to avoid memory fragmentation in system with limited memory (any modification of code would introduce unusable holes). If that's the case, what you want is an offset rather than an absolute address.
- Someone 1y ago
  > I get the impression that they were storing everything sequentially in memory, rather than having a linked list of instructions. Why? I can only speculate. I expect that’s because that is how ‘every’ homecomputer basic did it. Yes, that makes it slow to insert or remove a line close to the start of a long program, but it allow those offsets to be 8 bits, gaining a precious byte over a 16-bit absolute address. Now, why they initially chose to waste those bytes? I wouldn’t know, but I guess that, because (FTA) “The CP1610 processor cannot address directly the internal memory in byte terms, instead everything is handled by full word”, they didn’t think of using a single byte.
Someone 1y ago
> Mmm. IIRC, usually the compiled NEXT statement would store the pointer to the corresponding FOR statement, so you don't need an additional stack for loop depth during the execution I think you do. Apart from common sense, nothing forbids one from writing stuff like 100 for i = 1 to 10 110 if i = 4 gosub 100 120 print i 130 next 140 return I think many basics also allowed changing that goto 100 to goto 200 and adding 200 for j = 1 to 4 210 print i 220 print j 230 next Yes, things would likely end badly, but the basic interpreter would not be smart enough to reject such programs. Its editor didn’t even guarantee that a for statement had a corresponding next or vice versa; all it guaranteed was that the program consisted of a list of lines that each in isolation are valid basic code.
- 1y ago

analog8374 1y ago

I love basic Can you OOPize it?

zanderwohl 1y ago
Yes, meet Visual Basic 6. It has many OO features stapled on.
- pasc1878 1y ago
  Or VB.Net for more OOP
- turtleyacht 1y ago
  Classic ASP (Active Server Pages), and take it to the web.
andsoitis 1y ago
The following BASIC implementations support OOP: - Visual Basic .NET - PureBasic - XoJo - FreeBASIC - Gambas - PowerBASIC You can peruse various implementations, IDEs, and tutorials here: https://github.com/JohnBlood/awesome-basic https://github.com/JohnBlood/awesome-basic

____tom____ 1y ago

For those interested in BASIC, here's "A curated list of awesome BASIC dialects, IDEs, and tutorials": https://github.com/JohnBlood/awesome-basic?tab=readme-ov-file https://github.com/JohnBlood/awesome-basic?tab=readme-ov-fil... It's not as popular as Python, obviously, but that lists over fifty implementations of BASIC.

bluedino 1y ago

I always wondered if any engineers suggested changes to make some BASICs faster and the companies didn't want it competing with "real" software

3036e4 1y ago

There is a chapter in the Blue Book about how the GW-BASIC byte code is structured, and from what I understand it used pointers to lines, not just offsets? But I did not look too carefully (guess the answer is in the source code: https://gitlab.com/tkchia/GW-BASIC https://gitlab.com/tkchia/GW-BASIC). That book is full of interesting facts and fun low-level tricks for (GW-)BASIC programming. Available for download here: https://github.com/robhagemans/hoard-of-gwbasic https://github.com/robhagemans/hoard-of-gwbasic Before reading that I never considered how primitive early BASICs were. There is a lot of linear-searching for things (variables, line-numbers) that has to be considered when optimizing.

wkjagt 1y ago

Oscar Toledo (nanochess) is one of my personal heros. And one of his books, Boot Sector Games, is one of my favorite books. Seeing him post something like he just did gives me a kind of joy that is becoming pretty rare on the internet these days, for me at least.