I’ve used a basic program on C64 in the past and a Cartridge machinecode monitor in the past.
I’ve really forgotten how, what i’ve used and what i’ve done with it.
Not nearly as much as my friends at that time.
I started with a Vic-20 and played around with machinecode on a 6502.
I didn’t have a C64 for many years.

I’ve recently started to build a 6502 computer again, and programming on 65xx again (Generic 6502 and C64). (2022)

Below is my setup on linux, to write assembly code, compiling and running the code in a emulator.

I have installed the Acme compiler and Vice as a emulator.
Both can compile/run machinecode for multiple computer emulations. So maybe i can run my old Vic-20 machine code or the few C64 programs i’ve written.

I’ve only made the bash script, the included asm files i copied from someone on the internet. ( Credit lookup )

makeprg bash file:

#!/bin/bash
set -x
f=""
if [ "$2" == "f" ] ; then f="-fullscreen" ; fi 
if [ ! -f $1.asm ] ; then
cp template.asm $1.asm
fi
vi $1.asm
acme --cpu 6510 --format cbm --outfile $1.prg $1.asm
if [ ! $? -eq 0 ] ; then exit 1 ; fi 
c1541 -format foo,id d64 $1.d64 -write $1.prg
if [ ! $? -eq 0 ] ; then exit 1 ; fi 
x64 $f $1.prg 

template.asm

!source "basic-boot.asm"

+start_at $0900

; Set background and border to black
ldx #$00
stx bgcol
stx bocol

; Flicker border and background
.loop
  inc bgcol
  inc bocol
  jmp .loop

basic-boot.asm

; A BASIC booter, encodes `10 SYS <address>`.
; Macroified from http://www.pouet.net/topic.php?which=6541

!source "constants.asm"

!macro start_at .address {
  * = basic
  !byte $0c,$08,$00,$00,$9e
  !if .address >= 10000 { !byte 48 + ((.address / 10000) % 10) }
  !if .address >=  1000 { !byte 48 + ((.address /  1000) % 10) }
  !if .address >=   100 { !byte 48 + ((.address /   100) % 10) }
  !if .address >=    10 { !byte 48 + ((.address /    10) % 10) }
  !byte $30 + (.address % 10), $00, $00, $00
  * = .address
}

; A cooler example is to write
;
;   10 SYS <address>: REM <backspaces>Your comment
;
; When the user types LIST, he will just see
;
;   10 Your comment
;
; but still be able to run it.
; For this, see http://codebase64.org/doku.php?id=base:acme-macro-tu

When running above bash script. it will open the file if it exists, else it will take a template file.
After opening it with vi, and editing it, it starts a the compiler and creates a C64 d64 disk.
This is going to be autorun/started with the VIce emulator.
Appending -f to the bash script will start it in fullscreen mode.
./makeprg myawesomedemo.asm -f

Below it is running without the fullscreen option. but is shows how to start the interactive monitor in vice.

• n – step x instructions
  n 100
• m monitor

(C:$103e) m
>C:103e  cd 12 d0 d0  fb a2 00 bd  5c 10 bc 79  10 88 d0 fd   ........\..y....
>C:104e  8d 20 d0 8d  21 d0 e8 e0  1d d0 ec 4c  81 ea 06 00   . ..!......L....
>C:105e  0e 06 0e 0e  03 0e 03 03  01 03 01 01  01 01 03 01   ................
>C:106e  03 03 0e 03  0e 0e 06 0e  00 06 00 07  09 09 09 09   ................
>C:107e  09 09 09 07  09 09 09 09  09 09 09 07  09 09 09 09   ................
>C:108e  09 09 09 07  09 09 09 09  00 00 00 00  ff ff ff ff   ................
>C:109e  00 00 00 00  ff ff ff ff  00 00 00 00  ff ff ff ff   ................
>C:10ae  00 00 00 00  ff ff ff ff  00 00 00 00  ff ff ff ff   ................
>C:10be  00 00 00 00  ff ff ff ff  00 00 00 00  ff ff ff ff   ................
(C:$10ce) 

• d -assemble

(C:$1041) d 1000
.C:1000  78          SEI
.C:1001  A5 00       LDA $00
.C:1003  8A          TXA
.C:1004  98          TYA
.C:1005  8D 20 D0    STA $D020
.C:1008  8D 21 D0    STA $D021
.C:100b  A0 7F       LDY #$7F
.C:100d  8C 0D DC    STY $DC0D
.C:1010  8C 0D DD    STY $DD0D
.C:1013  AD 0D DC    LDA $DC0D
.C:1016  AD 0D DD    LDA $DD0D
.C:1019  A9 01       LDA #$01
.C:101b  8D 1A D0    STA $D01A
.C:101e  A9 39       LDA #$39
.C:1020  A2 10       LDX #$10
.C:1022  8D 14 03    STA $0314
.C:1025  8E 15 03    STX $0315

Etc .. see https://vice-emu.sourceforge.io/vice_12.html