' Reads a byte from 'pc' and increments 'pc'
Function rp()
 If pc >= FILE_LEN Then
   Error "PC " + Str$(pc) + " > file length " + Str$(FILE_LEN)
 EndIf
 rp = m(pc)
 pc = pc + 1
End Function

' Reads a byte from 'a' but DOES NOT increment a
Function rb(a)
 If a >= FILE_LEN Then
   Error "Address " + Str$(a) + " > file length " + Str$(FILE_LEN)
 EndIf
 rb = m(a)
End Function

' Reads a 16-bit word from 'a' but DOES NOT increment a
Function rw(a)
 If a >= FILE_LEN - 1 Then
   Error "Address " + Str$(a) + " > file length " + Str$(FILE_LEN)
 EndIf
 rw = m(a) * 256 + m(a + 1)
End Function

' Writes byte 'x' to 'a'
Sub wb(a, x)
 If a >= BASE_STATIC Then
   Error "Address for write is invalid: &h" + lpad$(Hex$(a), 4, "0")
 EndIf
 If x < 0 Or x > 255 Then Error "Value for write is invalid: " + Str$(x)
 m(a) = x
End Sub

' Writes 16-bit word 'x' to 'a'
Sub ww(a, x)
 If a >= BASE_STATIC - 1 Then
   Error "Address for write is invalid: &h" + lpad$(Hex$(a), 4, "0")
 EndIf
 If x < 0 Or x > 65536 Then Error "Value for write is invalid: " + Str$(x)
 m(a) = x \ 256
 m(a + 1) = x Mod 256
End Sub

Sub mem_init(f$)
 Local ad, i, j, s$, sz

 Print "Loading '"; f$; "'"

 sz = mm.info(filesize f$)

 ' Storage for z-machine memory.
 ' Each z-machine byte is stored as a MMBasic float (4 bytes).
 ' Terribly memory inefficient, but likely to provide the fastest memory access.
 Dim m(128 * 1024 - 1)

 Open f$ For Input As #1

 Print "0% ... ";
 j = 1
 Do
   s$ = Input$(255, #1)
   If Len(s$) = 0 Then Exit Do
   For i = 1 To Len(s$)
     m(ad) = Peek(Var s$, i)
     ad = ad + 1
   Next i
   If ad > j * sz \ 10 Then Print Str$(j * 10) + "% ... "; : j = j + 1
 Loop
 Print "100%"
 Print "Read"; ad; " bytes"

 Close #1

 ' Read header data.
 Dim pc = m(&h06) * 256 + m(&h07)
 Dim GLOBAL_VAR = m(&h0C) * 256 + m(&h0D)
 Dim BASE_STATIC = m(&h0E) * 256 + m(&h0F)
 Dim FILE_LEN = (m(&h1A) * 256 + m(&h1B)) * 2

 If FILE_LEN > ad Then Error "Story file is truncated"
End Sub

open mailbox
take leaflet
read leaflet
south
east
open window
enter window
take all
open sack
west
take all
open trophy case
move rug
open trap door
turn lantern on
down
n
i
quit
y

*replay

[execute:24] Error: EXEC is not declared

cls
Xmax = MM.HRES
Ymax = MM.VRES

for count = 1 to (RAND(1000) + 500)
 pixel RAND(Xmax), RAND(Ymax), map(RAND(255))
next count

end

function RAND(max)
 RAND = int(rnd() * int(max))
end function

 pixel (RAND(Xmax)), RAND(Ymax), map(RAND(255))

You can call RUN from within a program with some restrictions.

RUN "myprog.bas" is OK but
RUN myprog$ is not.

dim myprog$,path$

path$ = "A:/" : myprog$ = "speedtest.bas"

RUN ""+path$+myprog$+""