What is Excel 4.0 Macro?

Question

When I tried to insert a new sheet, I was given multiple options which I could choose from. One is obviously "Worksheet", another is called "MS Excel 4.0 Macro". So I chose "MS Excel 4.0 Macro", and it looks exactly the same as a new worksheet. I'm just curious what is the difference between a regular worksheet and MS Excel 4.0 Macro sheet?

Answer 1

History
From its first version Excel supported end-user programming of macros (automation of repetitive tasks) and user-defined functions (extension of Excel's built-in function library). In early versions of Excel, these programs were written in a macro language whose statements had formula syntax and resided in the cells of special-purpose macro sheets (stored with file extension .XLM in Windows.) XLM was the default macro language for Excel through Excel 4.0. Beginning with version 5.0 Excel recorded macros in VBA by default but with version 5.0 XLM recording was still allowed as an option. After version 5.0 that option was discontinued. All versions of Excel, including Excel 2010 are capable of running an XLM macro, though Microsoft discourages their use.

^{https://en.wikipedia.org/wiki/Microsoft_Excel}

The purpose of MS Excel 4.0 Macro sheets is to run legacy Excel 4.0 macros. Microsoft replaced Excel 4.0 Macros with VBA in 1993, but they can still be run. Now (almost 30 years later), this is most extensively used by malicious parties (hackers).

For example, you can enter the following into A1:A2:

=EXEC("calc.exe")
=HALT()

Then, to run it (to open the Calculator) you would need to right click A1 and choose Run... -> Run. All the formulas downwards from the clicked cell will be evaluated.

PDF containing the complete Excel 4.0 macro functions reference