---
title: "G-Code Test for a Job Interview: What to Study and How"
description: "What a G-code test in a CNC job interview usually covers, the codes to know cold, and a fast way to drill them before you walk in."
url: https://gcodepractice.com/journal/g-code-test-for-job-interview/
canonical: https://gcodepractice.com/journal/g-code-test-for-job-interview/
author: "Lawrence Arya"
authorUrl: https://www.linkedin.com/in/vibecoding/
published: 2026-06-02
updated: 2026-06-02
category: "Practice"
tags: ["interview", "test prep", "g-code", "beginner"]
lang: en
---

# G-Code Test for a Job Interview: What to Study and How

> **TL;DR** A G-code test for a job interview usually checks that you can read a short program and recall what the common codes do: G00, G01, G02, G03, the spindle codes M03 and M05, and basic setup codes. You will not need exotic codes. The fastest prep is active recall of the common G-code and M-code, drilled until the answers are instant.

A G-code test in a CNC interview is rarely about trick questions. It checks one thing: can you read a program and say what it does without reaching for the manual. That is recall, and it is exactly what you can practice in advance.

## What they actually ask

Most beginner and operator interviews stay close to the codes you would meet in your first weeks:

- **Read a short block.** "What does `G01 X50 F150` do?" (a straight feed move to X50 at 150 units per minute).
- **Code to meaning.** "What is `G00`?" (rapid positioning).
- **The common mix-ups.** `G00` vs `G01`, or `G02` vs `G03`.
- **Spindle and safety basics.** What `M03` and `M05` do, and why you stop the spindle before a tool change.

You will almost never be asked for an obscure canned cycle on the spot. The point is fluency with the basics.

## The codes to know cold

| Code | Meaning | Why it comes up |
| --- | --- | --- |
| `G00` / `G01` | Rapid / linear feed | The two most common moves |
| `G02` / `G03` | Clockwise / counterclockwise arc | Tests direction recall |
| `G20` / `G21` | Inch / millimeter units | Easy to overlook, easy to test |
| `G90` / `G91` | Absolute / incremental | Shows you understand modes |
| `M03` / `M05` | Spindle on (CW) / stop | Spindle basics, safety habits |

If you can answer every row above instantly, in both directions, you are ready for the code portion of most interviews. The deeper breakdowns live in [common G-codes for CNC beginners](/journal/common-g-codes-for-cnc-beginners/) and [common M-codes for CNC beginners](/journal/common-m-codes-for-cnc-beginners/).

## How to prep in a week

Reading a cheat sheet builds recognition, not recall, so it falls apart under interview pressure. Drill retrieval instead: see a code, answer from memory, check, repeat. Spend extra reps on the pairs you confuse, like [G00 vs G01](/journal/g00-vs-g01/). The full method is in [beginner CNC code practice](/journal/beginner-cnc-code-practice/), and a timed mode (like the one in [G-Code Sprint](/g-code-practice/)) is useful because it rehearses answering quickly, which is the part interviews actually test.

For worked examples, see [CNC practical test examples for a job interview](/journal/cnc-practical-test-examples-for-job-interview/). If you are interviewing abroad, the same fundamentals apply, as covered in [CNC operator jobs in Dubai test questions](/journal/cnc-operator-jobs-dubai-test-questions/). And before you run anything on a real machine, understand [how to safely test a program without crashing](/journal/how-to-safely-test-a-g-code-program-without-crashing/).

## Bottom line

A CNC interview G-code test checks fluency with the common codes, not exotic ones. Drill the motion codes, units, positioning, and spindle basics with active recall and a timer, and the code questions become the easy part of the interview.

## Sources

- [NIMS (National Institute for Metalworking Skills)](https://www.nims-skills.org/)
- [LinuxCNC G-code quick reference](https://linuxcnc.org/docs/html/gcode/g-code.html)
- [CNCCookbook: G-code and M-code cheat sheet](https://www.cnccookbook.com/g-code-m-code-cnc-list-cheat-sheet/)

## Frequently asked questions

### What G-codes come up most in CNC interviews?
The motion codes `G00`, `G01`, `G02`, and `G03`, the spindle codes `M03` and `M05`, units (`G20`/`G21`), and positioning (`G90`/`G91`). Interviewers want to see you can read a short program, not recite the whole standard.

### How long should I study for a CNC interview test?
A few short sessions over a week is enough for most beginners if you use active recall. Cramming the night before fades fast; spaced drills stick.

### What is the best way to prepare for a G-code interview test?
Drill the common codes with active recall instead of re-reading a chart. A free tool like G-Code Sprint has a timed mode that mimics interview pressure and a weak-code review that focuses on what you keep missing.

*G-Code Sprint is a study and practice tool only. Always follow your instructor, employer, machine manual, and shop safety procedures.*

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Source: https://gcodepractice.com/journal/g-code-test-for-job-interview/
Author: Lawrence Arya — https://www.linkedin.com/in/vibecoding/