# Macro Creation Tutorial **URL:** \ **Category:** Macros\ **Created:** [March 22, 2021, 3:00pm UTC](https://klipper.discourse.group/t/macro-creation-tutorial/30 "2021-03-22T15:00:59Z")\ **Posts on this page:** 1\ **Showing post:** 2
**Author:** ![mental](https://yyz2.discourse-cdn.com/free1/user_avatar/klipper.discourse.group/mental/32/11_2.png) [@mental](https://klipper.discourse.group/u/mental)\ **Post date:** [March 22, 2021, 4:00pm UTC](https://klipper.discourse.group/t/macro-creation-tutorial/30/2 "2021-03-22T16:00:21Z")
**Part 1: Basic Programming Concepts** Klipper macros are quite powerful, but at the same time can be limited in their scope. The idea for macros is to be able to make some basic decisions and act on them by substituting various values with other values. To understand macros, though, we must first understand some programming basics **What is a function?** A function is a bit of code that produces output based on the input. Typically decisions are made inside of a function via expressions that determine what the function should do. Functions can also be called methods, routines, procedures. They all do basically the same thing: Take a block of code and give it a name so it can be reused to produce output based on input. **What is a literal?** A literal is a value that is effectively hard coded and cannot be changed throughout the execution of a program. For instance, a integer value of `42` is a literal. The value of `42` is literally `42`. **What is a comment?** The intended use of a comment is for the person writing code to leave notes for themselves or anyone else should they come back and try to understand the code later. Comments are denoted by a special character or set of characters specific to each programming language. In the case of Klipper config files and macros, there are two such characters used to denote a comment. `#` and `;` . When Either of these appear on a line, anything after them will be ignored. ```auto #Move the toolhead to the middle of the bed G1 X150 Y150 #Move the toolhead up slightly G1 Z1 ``` Comments can also be beneficial for debugging or changing code around. If you have a bit of code that might not be working right or you want try to make it do something else, but don’t want to delete the original bit in case it doesn’t work, you can “comment out” that bit of code ```auto #Move the toolhead to the middle of the bed #G1 X150 Y150 #Move the toolhead up slightly G1 Z1 ``` In the example above, the newly commented line will be ignored when it comes time to execute the macro. **What is a variable?** A variable is a value that can change throughout the execution of a program. Variables are typically represented by names or letters. The name is associated with a value because the value can change. When the variable name is referenced during the execution of a block of code, the name is substituted for the value of the variable at the time the expression is executed. So if we take our literal `42` and assign it to a variable called `e` whenever `e` is referenced, the value `42` will be used. **What is an assignment?** Giving a value to a variable is done by assignment. This can be a literal value, the value of another variable, or the result of an expression. An assignment is done by setting the variable equal to a value. In Jinja2 syntax, this is done with ```auto { set x = 42 } ``` **What is an expression?** An expression is a programming command that does something. A simple example would be a gcode command. `M105` is a gcode expression that reports the various temperatures. A variable assignment is also an expression. A comparison of two values is an expression. In the simplest terms, an expression is a bit of code that produces a result or value. **What is an object?** An object is a collection of variables, states, functions, and possibly more objects. Objects are used to organize and access entities in a program. For instance, in Klipper macros, there is a `printer` object which has another “fan” object attached to it. The fan has a “speed” variable which is used to both get and set the fan speed. To get the fan speed, one would use ```auto printer.fan.speed ``` **What is a parameter?** A parameter is a value that is used as the input for the execution of a function. In gcode, the function would be the gcode command and the parameters would be the axis positions and speeds. ```auto G1 X100 Y24 Z1 F2000 ``` In other programming languages like python, functions are represented by a name and the parameters are enclosed in parenthesis after the name. ```auto action_respond_info("String Literal") ``` **What is a conditional?** Similarly, expressions can also evaluate two things. Conditionals answer a `Yes` or `No`, `True` or `False`, `1` or `0` question by evaluating one variable or literal against another variable or literal. This is “boolean” logic and it is at the core of all programming. ```auto Is 15 equal to 12? False Is EXTRUDER_TEMP > 100? True ``` Similarly, functions can return a value after they execute and that value can be compared in an expression as well. There say you have a function called `EXTRUDER_PERCENT_TO_TARGET()` and it takes two parameters. It returns the percentage of the `CURRENT_TEMP` to the `TARGET_TEMP` ` Is EXTRUDER_PERCENT_TO_TARGET( CURRENT_TEMP, TARGET_TEMP ) > 70? False` **What is a macro?** A macro is a stored set of commands that can be called from a single gcode command. Macros can call other macros or even themselves. Macros can be treated like functions. For all intents and purposes, a klipper macro is a function. **What is a Jinja?** Jinja is an engine for python (Klipper’s primary language) that can take a block of text and read programming elements out of it. In the case of gcode macros those programming elements are applied as a command template. A command template could be looked at like a paragraph of fill in the blanks. Like Mad Libs meets Choose Your Own Adventure. When the gcode macro is called, the entirety of the command template is read in and evaluated. The gcode that is expressed back to klipper is the result of whatever decisions were made inside of that macro. **What is delayed gcode?** Delayed gcode is a macro that cannot be called directly, but is instead called and executed from a timer at a set interval. Delayed gcode can run once or repeatedly --- _[View the full topic](https://klipper.discourse.group/t/macro-creation-tutorial/30)._