Self modifying code, lambda calculus - Re: ENIAC programming

[Liam Proven]

On 19 September 2015 at 17:02, Rod Smallwood
<rodsmallwood52 at btinternet.com> wrote:
> Its a while back but I seem to remember in BASIC you replaced a set of line
> numbers with another of the same range but different code.

Blimey, I've never seen that.

I do remember that ZX BASIC had a cool-but-dangerous feature: you
could get it to evaluate an arbitrary string as if it were an
expression. This meant you could do cool things in BASIC programs --
enter formulae such as "2*4+3.5" when the program wanted a numeric
value, for instance.

Then a friend showed me that you could also access the program's own
variables. If the program had variables called a, b & c, you could
also enter "a*b+c" and it would use the values.

Which meant that if it /didn't/ have such variables, the program would
crash out with an "unknown variable name" error... a sort of early
"exploit".



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