double d_pi_clicks = double(PI_VALUE) * double(MAX_ENCODER_CLICKS) ; Why do American universities have so many general education courses? I am having issues with my int reaching the max value of 32767 and am looking for an alternative. I did a write up here, with a simple explain of how much RAM is used (checked with avr-size) when using const and when not: Arduino boards have microcontrollers with notoriously small amounts of RAM. While James clearly doesn't like #define's, they do have their place. However, it is still a variable and depending on how it is used in the code, may or may not consume RAM. You can even see that it is there by issuing: xxd test | grep ONE_E The reverse is also possible, although probably less common. And I believe reference and dereference are not the terms you are looking for. If you find this answer helpful please upvote the answer so other people will also take benefit from it. Hence its much better they steer clear of #define. Most often, an int is two bytes (32767 max) or four bytes (>2 billion max). Python offers simplicity, but at the cost of run-time resources. Massive list of compile errors last time I tried to add the library, even without doing anything to it. But today and especially for something like a simple value, a const int would generally be preferred over a #define as it can be safer to avoid #define so you can avoid some silent issues. A #define is a preprocessor macro, not a variable. In either case, I think it helps to upper-case both #define's and const data definitions to signal the reader that the expression is different. But I think that's the right terminology. Just refer to it in the JSON string and somehow end up with a pointer to it. Because a #define is a textual replacement, it is "typeless". Or is it a matter of choice? // It doesn't work well, because you can't use it in many situations where the compiler wants a 'real' constant. #define DEF ABCDEFG We find this answer accurate for define() vs. const. How could my characters be tricked into thinking they are on Mars? Unless, that is, you really want the pre-processor to replace all instances of ledPin with = 13, which is unlikely. Site design / logo 2022 Stack Exchange Inc; user contributions licensed under CC BY-SA. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. declares a variable, not a pointer. Powered by Discourse, best viewed with JavaScript enabled. I've looked at loads of code and have come across a puzzle. #defines can't be type checked, so this can cause problems when trying to determine the data type. It can catch some types of programming errors or typos. econjack: There are simply no reasons to prefer #define over const, aside from few exceptions. #define is a useful C++ component that allows the programmer to give a name to a constant value before the program is compiled. Is replaced with Agree The difference is that const int creates a variable, and #define is a macro in the language, it swaps out the word with the number whenever it is encountered. #define ABC 123.456 * 789 In this case, it works, since both the declaration and definition are visible. Defined constants in arduino don't take up any program memory space on the chip. Const values defined like this are not visible for the actual compiler, while a variable defined with the const modifier is an actual typed "variable" (well not really that variable). But in regard to the OPs questionand their level of experience I stand by my statement and judgement that they do not need to be confused by a full explanation at this point. Connect and share knowledge within a single location that is structured and easy to search. The -g flag asks gdb to add debugging information to the binary. Because a #define is a textual replacement, it is "typeless". In the definition of function parameters, which is called formal parameters. The compiler will replace references to these constants with the defined value at compile time. The other example works without. For example: Appealing a verdict due to the lawyers being incompetent and or failing to follow instructions? If you've done sufficient Arduino programming, you'd have seen that there are two ways of defining constants. double() is required, or it doesn't calculate correctly, When compiled, the version with consts uses the same variable storage memory, and LESS programming space I am looking for the source and/or proper definition for the int() function. It is a variable qualifier that modifies the behavior of the variable, making a variable " read-only ". you can also #define anything. They take up program memory space, and have a type (which is advantageous in many situations). Everything was working, I added a few new functions, and started getting strange results in functions that had been working before, and nothing had changed. You can add -std=c++11 to platform.txt for now (1.5.7). define el cdigo HTML, que es convertido en componentes nativos de interfaz, esto es llamado el VirtualDOM (Jimenez, 2019) . So in the header I have this signal for the power button on a remote: Some of you might recognise this data format as cribbed straight from the tutorials on IRLib2. (can change dynamically). OP- If you are still with us C secara tradisional digunakan #defines untuk konstanta. Its a mistake if you ask me, some warnings will point out logic errors which will compile fine. A const variable is only ever one type, which is determined by its declaration, and resolved during initialisation. bool doIHaveTheThing[COUNT_OF_THINGS] = {false, false, false, false, false]; // Doesn't compile! i.e. But since #define is a pre-processor feature, it can be used for so much more. The Uno only has 2,048 bytes of static RAM available for your program to store variables. That means it impacts available Flash for any type that takes up more space than a pointer. char *search ( char *s, char *t ); searchs t ts. A byte stores an 8-bit unsigned number, from 0 to 255. For example, when using pull-up resistors on my buttons, I usually do this: As for #2, the compiler is pretty smart. If you are using #define for simple constants, then 'constexpr' is preferred over 'const'. This is different from const int X = Y; which goes directly into the compiler. Difference between signed and unsigned integer in Arduino. I'm very rusty on my C++ so forgive me if this isn't a question about dereferencing at all. A lot of it comes down to personal preference, however it is clear that #define is more versatile. This is going to introduce confusing compiler messages and a difficult to locate bug MisterG: you might be interested in looking at stdint.h under Arduino/hardware/tools/avr/avr/include. An int can be modified when you need, it is read/write and a const int is read only. Learn more, Difference between #define and const in Arduino, Difference between #define and const in C. What is the difference between #define and const Keyword in C++? What can we do with questions 'bumped' by Community bot? A possible workaround for this is to include an explicit cast or a type-suffix within a #define. The general form given in the documentation is as follows: String tables are a bit more complicated, but the documentation has full details. At least that way you get a proper build environment - and can even change the compiler options if you want. Yes, Im aware of how to use #define properly and that what I wrote was an over simplification. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, I'm having hard time to understand what you were trying to do. Thanks for the thorough reply. bperrybap: "static const" vs "#define" in c When I do this : #define WEEKDAYS 7 and that : const int WEEKDAYS = 7; Any difference between them ? The const int is a better style than the #define. Why does the distance from light to subject affect exposure (inverse square law) while from subject to lens does not? Description. On an 8-bit microcontroller with 2,048 bytes of RAM, resources matter. It can be used in C++, but there are better ways. I guess they base it on the fact newbies can't understand the messages spewed out. What is the difference between const int*, const int * const, and int const *? How do I parse a string to a float or int? const int . const int boolSize = Data [0].BoolSize; so what i want is, i dont want to predefine the boolean size in the cpp code. We make use of First and third party cookies to improve our user experience. You would use 'constexpr' like you would use 'const', except that this tells the compiler that the value MUST be known to the compiler at compile time. I use const int to define an integer variable that is not allowed to change. Is there any reason on passenger airliners not to have a physical lock between throttles? Really? Description. c++ constants c-preprocessor Share Follow edited May 23, 2017 at 12:18 Community Bot 1 1 asked Aug 25, 2012 at 16:26 JAN CGAC2022 Day 10: Help Santa sort presents! It depends on what you need the value for. Using const int i_variable_for_whatever does NOT use memory under ant circumstances that I have encountered so far. Log in or register to post comments; Top. I tend towards #define, but I see some code using const and some using a blend. I often like this because: So in an idiomatic C++ program, there is no reason whatsoever to use #define to define an integer constant. I need an efficiant way to Stack Exchange network consists of 181 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. . A #define (preprocessor macro) directly copies the literal value into each location in code, making every usage independent. There are two different approach you could use to get to similar effect (I guess). Maybe it was an out of date library or something. True, but it can assume the resolved data type used in the expression. pcbbc: Cada una de ellas tiene su explicacin. Easiest way to convert int to string in C++. Allow non-GPL plugins in a GPL main program. Is this possible and if so, can someone give me an example? Does balls to the wall mean full speed ahead or full speed ahead and nosedive? Moreover, I always like to have my pin definitions up at the top all in one place, so the question becomes which type of const would be appropriate for a pin defined as A5. Ahh, my mistake. The other way is to use the const keyword, like. Guide to the C++ language constexpr keyword. How do I tell if this single climbing rope is still safe for use? It will often require an explicit cast before it will behave differently (although there are various situations where it can safely be implicitly type-promoted). Arduino adalah hibrida aneh, di mana beberapa fungsionalitas C ++ digunakan di dunia yang disematkan biasanya lingkungan C. Memang, banyak kode Arduino sangat C seperti. . and their level of experience I stand by my statement and judgement that they do not need to be confused by a full explanation at this point. PROGMEM At least because such constants are typed and scoped. const int * And int const * are the same. True, but compiling with the default settings for the IDE is alarmingly quiet, and those are the settings that most newbies use. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. If you ever face confusion in reading such symbols, remember the Spiral rule: Start from the name of the variable and move clockwise to the next pointer or type. 'const' is just a hint for the compiler. means that when you use DEF you'll get XYZDEFG not ABCDEFG, once I knew that, I was far more careful, but still used defines instead of consts In 1.0.5/1.5.3 and greater, you only get error messages. Memory usage The constants in Arduino are defined as the predefined expressions. the const int will be put into ram memory define will go through the code at compile and substitute ledPin with 13 however your compiler might do the same with const to save some ram, it all depends on how its compiled. This yields a range of -32,768 to 32,767 (minimum value of -2^15 and a maximum value of (2^15) - 1). #include <stdio.h> #define MAXS 30 char *search ( char *s, char *t . At the very least, the compiler can (if configured correctly) emit a more reliable warning when a type issue occurs. What is the main difference between these when naming a variable? They take up program memory space, and have a type (which is advantageous in many situations). Gives a compile error (already defined, because ABC is replaced with XYZ in the second line), #define ABC XYZ You can't use const int as case statement labels (though this does work in some compilers). Effectively, this implies that the pointer shouldn't point to some other address. If anyone cares, #define X Y causes the preprocessor to do a replacement of any symbol X in your code to symbol (s) Y before the code is run through the compiler. The other example works without. Para explicarlo de la manera ms sencilla, supongamos que definimos lo siguiente: Most often, an int is two bytes (32767 max) or four bytes (>2 billion max). That last sentence is not accurate. The maximum positive value of an "int" depends on the compiler. It's not quite correct to say that a compile-time constant uses no storage though, because its value still has to occur in code (i.e. Would it be possible, given current technology, ten years, and an infinite amount of money, to construct a 7,000 foot (2200 meter) aircraft carrier? #define ledPin = 13is not correct. You can even initialize a constexpr with another constexpr: Furthermore, constexpr guarantees that the variable gets evaluated at compile-time, unlike const. Which is good for things that shouldn't change while your program runs, e.g. And if you have another remote, with a different name, you would need to create a whole new macro function, to get them to work. In that case, the compiler would print 1 instead of ONE_E. Since (2) is apparently an option, you don't . define and const are not technically the same thing, but they do accomplish the same goal. Physically, as far as the Arduino is concerned there is absolutely no difference. What is difference between int and const int& in C/C++? What's the difference between #define and const int when declaring a pin? #define XYZDEF ABCDEFG const double cd_pi_value = 3.14159 ; There is an interesting Arduino Forum thread that discusses other ways to decide: #define vs. const variable (Arduino forum), Defining true and false as Boolean to save RAM. This is a great example of why #define shouldn't be used. XC32 sees it as a variable that does not change, but as variables can change, even if they can't, they are no good as used above. Normally, if the compiler assigns a "smaller" data type into a "larger" data type (e.g., long = int), the silent cast is done without fanfare. All the setup variables are right at the top and there is never going to be a change to the value of adcPin except at compile time. As pointers on a machine that has 16-bit addressing will be 2 bytes wide, the differences by using #define and const int are negligible, just in access time (SRAM is faster). First you can utilize macros. Better way to check if an element only exists in one array. Note that The second way is through OOP. Meaning of 'const' last in a function declaration of a class? constexpr also doesn't have some of the disadvantages that preprocessor macros have(learncpp): Thanks for contributing an answer to Arduino Stack Exchange! "const" makes the variable 'read only'. Its not type less at all, literal integers are a type of int, and will never be char/unsinged char, only character literals can be chars. While the compiler must use some default data type in the preprocessor pass, it's the resolution of that expression that makes it seem to be typeless. I'm glad my daughter is using the Raspberry Pi at the moment. We do not currently allow content pasted from ChatGPT on Stack Overflow; read our policy here. This is obviously different from a '#define', which is straight textual substitution. Well, to my surprise, This means that the variable can be used just as any other variable of its type, but its value cannot be changed. Sure, you can hard-code the pin numbers as a2, a3, etc. They are both integer variables, but the last one is also a constant. It exists at all times, not just when the function is called and so takes a constant amount of memory. On a PC (or SBC like a Pi), there are usually plenty to spare. const restricts your ability to modify the value. but you can not change the assigned value of ledpin throught out its scope. '#define' is used similarly to 'const int'. Or is it a matter of choice? Is it important to declare it as such? It is easy to accidentally forget to declare the constant as "long". pYro_65: No worries about what type adcPin is. Why is the federal judiciary of the United States divided into circuits? But today and especially for something like a simple value, a const int would generally be preferred over a #define as it can be safer to avoid #define so you can avoid some silent issues. How to convert a std::string to const char* or char*. Why is Singapore considered to be a dictatorial regime and a multi-party democracy at the same time? you are creating a variable (ledpin) of int data type and assigning 13 to it. Asking for help, clarification, or responding to other answers. (Might not for this example, but it did for me full sketch), So, after 36 years of programming, I have changed my use of constants and defines (on the arduino at least), Powered by Discourse, best viewed with JavaScript enabled, Const vs #define - When do you use them and why? const int isnt a variable, it is a constant. I hadn't seen "const byte" used in the (limited number of) examples I've seen, but I can see how it will save RAM in a bigger application. but you can change the assigned value of ledpin when ever you want. I was very careful to use the term "expression" in what I said. econjack: #define is a pre-processor directive, essentially a sort of macro. #define Es un macro que se ejecuta antes de la compilacin. You can even use them for some amount of namespace control. 4. Help us identify new roles for community members, Proposing a Community-Specific Closure Reason for non-English content. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. And if you are writing your code in C++ you can use. #define ABCDEF QWERTY If you used a define, you would not have a proper type to give e, and would have to use an integer. In general, it is preferred to use const over #define, for defining constants. Browse other questions tagged, Start here for a quick overview of the site, Detailed answers to any questions you might have, Discuss the workings and policies of this site, Learn more about Stack Overflow the company. Help us identify new roles for community members. Thanks again :). Since (2) is apparently an option, you don't need to pass pointers around. While the compiler must use some default data type in the preprocessor pass, it's the resolution of that expression that makes it seem to be typeless. When novices try to use #define we end up with code like and many other heinous misunderstandings of what they are doing. #define ABC_DEF 654.321 If it is not used in an array, then it will probably not save any RAM at all - generally const variables (which don't involve pointers) are simply optimised into 'ldi' instructions wherever they are used - much like #defines. Normally, integer constants are treated as base 10 (decimal) integers, but special notation (formatters) may be used to enter numbers in other bases. It only takes a minute to sign up. What is the difference between "const" and "val" in Kotlin? Find centralized, trusted content and collaborate around the technologies you use most. Enjoy unlimited access on 5500+ Hand Picked Quality Video Courses. The Arduino Uno has two interrupts, interrupt 0 and interrupt 1.Interrupt 0 is connected to digital pin 2, and interrupt 1 is connected to digital pin 3.. . It's important to note that const int does not behave identically in C and in C++, so in fact several of the objections against it that have been alluded to in the original question and in Peter Bloomfields's extensive answer are not valid: However, for integer constants, it might often be preferable to use a (named or anonymous) enum. En el lenguaje de Arduino, que no es otra cosa que C y C++, podemos declarar constantes usando #define y tambin const. static const : "static const" is basically a combination of static(a storage specifier) and const(a type qualifier). Should I give a brutally honest feedback on course evaluations? static const vs #define vs enum. In general, in C++ (which Arduino is based on), the best way to define constants is Continue Reading For example for the number 0, the binary form is 00000000, there are 8 zeros (8 bits in total). What happens if you score more than 99 points in volleyball? int is a variable. A different approach would be to use std::array instead a C-array. Sort of a roll my own namespace if you will. Asking for help, clarification, or responding to other answers. sketch_jul17a.ino:3:20: warning: large integer implicitly truncated to unsigned type @PeterR.Bloomfield, my point about constants not requiring extra storage was confined to. The Arduino compiler replaces all mentions of this constant with its value at the compile time. 'constexpr' is always defined at declaration, so if the name is visible it is usable. @Cybergibbons Arduino is based on C++, so it's not clear to me why C only constraints would be pertinent (unless your code for some reason needs to be compatible with C as well). Hence its much better they steer clear of #define. and. you can't have an array of #define). Do you mean if you can use the substring, I simple way to do it is to write a script (ksh, awk, python) to parse it and write the code for you. If you declare a variable (eg. Here are some guidelines which I would follow: Type safety This means that the variable can be used just as any other variable of its type, but its value cannot be changed. You can't create a variable name based on values from another string. Is a const int Is a const byte The compiler know when it can fit a number into one register and when it can't. However it is good practice to use coding that indicates your intent. 37Arduino37 . Arduino IDE 1.5.7 now has gcc 4.8.1 and C++11 will be turned on in 1.5.8. Is it better to use #define or const int for constants? It makes the code easy to read. You can't set array sizes using const int. const has a number of effects in C++. Static : determines the lifetime and visibility/accessibility of the variable. If I understand you correctly, using #define IS NOT strong typing because it uses the default data type, but by defining a "const" variable as an 8-bit unsigned integer (const uint8_t) you are telling the compiler what to use and not letting the pre-processor make that default determination. So would i use 'long int' to increase the 'int' value? #define MAX_ENCODER_CLICKS, double d_pi_clicks = cd_pi_value * ci_max_encoder_clicks ; That is: the code. Both (1) and (3) have a symbol in the debugger . But the I found an include that defined something that caused the same kind of problem. sketch_jul17a.ino:4:20: warning: large integer implicitly truncated to unsigned type What are constants? 2) #define is not scope controlled whereas const is scope controlled For some applications, it's quite easy to run out of SRAM, so it can be helpful to shift some things into Flash. The value of true and false are defined as 1 and 0. Is it important to declare it as such? That isn't too bad, it does get resolved properly, but, #define ABC XYZ The IDE itself still has a way to go, but its improving. That's a construct I use often. I've been Googling dereferencing variables in C++ but keep getting pages on pointers. Defined constants in arduino don't take up any program memory space on the chip. The first line ( static const int.) You raise some excellent points (especially about the array limits -- I hadn't realised the standard compiler with Arduino IDE supported that yet). Integers are your primary data-type for number storage. AND it is MUCH MUCH easier to ensure that calculations are type converted properly Difference between const int*, const int * const, and int const * in C. Difference between const int*, const int * const, and int const * in C/C++? But, if your 'const int' is declared but not defined, it doesn't. En la Figura 70 se encuentra un ejemplo simplificado en cdigo Arduino. For example, in many cases the compiler is required to allocate storage for these values, even though they never change! In fact, the compiler which avr-gcc IDE uses is smart enough to establish a variable that has a constant modifier can't be altered in an active program. RayLivingston March 22, 2019, 10:42pm #20 By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. There are a number of reasons for this: You can check this question on StackOverflow for more reasoning. There are many things you can do with macros that cannot be done with variables or writing out code longhand as macros are text substitution done on the source code before the compile is run. If you write "int a = 5;" that defines a variable with an initial value of 5 (and then you can set it to anything you want). So it is really about const vs. #define. Repeat until expression ends. The logical level constants are true or false. Its value is set at compile time and cant be changed. The disadvantage of #define is that is replaces . The main reason for that is type-safety. Can a prospective pilot be negated their certification because of too big/small hands? Description The const keyword stands for constant. Its the normal integral conversions which allow them to be converted and assigned, and the same rules apply regardless of weather the integer is a literal, variable, or constant. Theoretically, a #define will save space/CPU cycles since the data doesn't need to occupy and be stored and loaded from SRAM. I have seen -32767 to 32767 (which i thought was 'short int') and -2147483648 to 2147483648. Normally, if the compiler assigns a "smaller" data type into a "larger" data type (e.g., long = int), the silent cast is done without fanfare. #define is a useful C++ component that allows the programmer to give a name to a constant value before the program is compiled. Most often, an int is two bytes (32767 max) or four bytes (>2 billion max). sketch_jul17a.ino:5:18: warning: overflow in implicit constant conversion The term "const" informs the compiler a pointer or variable can't be changed. Macros can get very sophisticated especially if using some of the more advanced pre-processor capabilities like concatenation or pasting. Is what I am about to say correct? Furthermore, you could also make the Remote class without the name member, and store remotes in a map container: Now if you want to access a remote called "AKB" from the map, you can do things like: Thanks for contributing an answer to Stack Overflow! In general, it is preferred to use const over #define, for defining constants. Counterexamples to differentiation under integral sign, revisited. What I want to do is construct the variable or #define name from a string and then use that. Penrose diagram of hypothetical astrophysical white hole. Const qualifier doesn't affect the value of integer in this scenario so the value being stored in the address is allowed to change. #define asks the preprocessor to do a literal text-wise copy paste into the code before the compiler even sees it.. #defined values have no type, which prevents the compiler from throwing warnings for various code issues.. const int theoretically consumes RAM, however compiler optimizations will often annul any RAM usage if the variable is only used in one file and you never take its address . EDIT: microtherion gives an excellent answer which corrects some of my points here, particularly about memory usage. I was very careful to use the term "expression" in what I said. Sed based on 2 words, then replace whole line with variable, Books that explain fundamental chess concepts. Saving RAM is important, but the key reason to use const, in my opinion, is to make sure you (the programmer) doesn't make a mistake. BE SURE to check when moving between target machines and compilers. I really don't like arduino or want to have anything to do with it, seems that both do the same thing - sets a constant value for future usage within the code . Writers of embedded software often define these types, because systems can sometimes . Would salt mines, lakes or flats be reasonably found in high, snowy elevations? Sed based on 2 words, then replace whole line with variable. If it sees in your program a non-const variable is never modified, it may actually treat it as a constant, never putting it into RAM. Well, not really. const variables are considered variables, and not macro definitions. jremington: It is typeless in that it can be used in almost any expression where a data type is used and the compiler won't flag it as a type mismatch where a cast would normally be required. There are two different approach you could use to get to similar effect(I guess). It doesn't work for all types, but it's commonly used for arrays of integers or strings. So, what should we use for Arduino? pcbbc: It is a variable qualifier that modifies the behavior of the variable, making a variable " read-only ". The compiler will replace references to these constants with the defined value at compile time. I want to be able to quit Finder but can't edit Finder's Info.plist after disabling SIP. The implications for this specifically are a few bytes of memory. pin numbers. Site design / logo 2022 Stack Exchange Inc; user contributions licensed under CC BY-SA. c++ arduino Share Improve this question Follow #define is a pre-processor directive, essentially a sort of macro. If the IDE had a symbolic debugger, I would rarely use #define, since it cannot be traced by a debugger once the preprocessor pass completes. Depends on the compiler, GCC seems to be happy with it, XC32 (PIC) is not. I'm putting together an Arduino sketch to send out raw infrared signals to emulate IR controllers. Most importantly, they can't be used in very common situations where #define DOES work, for example as the size of an array. Such why I would for assigning to my Arduino UNO. Not the answer you're looking for? '#define' is used similarly to 'const int'. The quick answer would be no. rev2022.12.9.43105. MisterG: - Bald Engineer, http://arduino.cc/forum/index.php/topic,86800.15.html, to will let the compiler complain if your program tries to modify a value. I use const int to define an integer variable that is not allowed to change. SRAM and Flash have different limitations (e.g. How close am I? To achieve this I'm sending a JSON string that references the signal defined in a header file that I'm including. Memory usage: #define vs. static const for uint8_t, ESP8266 stops working when I use 2x static const char(PROGMEM), Use chars in quotes in const char* as name of function. I think the map suggestion is the most likely answer, but I've been struggling to get it to work on the Arduino. Plus, if you look at my answer below, I demonstrate that there are circumstances when you don't really know which type to use, so. RF receiver for integer only, how to cast uint8_t to int? Its too quiet to tell you the truth, some warnings would be useful. A uint8_t data type is basically the same as byte in Arduino. @bperrybap const int consumes RAM and has a type and a memory address, so you can pass &variable into functions that take a pointer to const int, and the compiler will complain if you put it somewhere that's not supposed to be an int.. #define asks the preprocessor to do a straight text-replace before the compiler ever sees any of your code, and so it doesn't consume RAM or have a type or a memory address. const int COUNT = 3; does not define a macro; it defines a name of a variable, and wherever that variable is used, the value 3 is used. 'int' is manly used as a counter, but my main issue is what is the max value for this variable? Personally I would suggest beginners steer clear of it. C has traditionally used #defines for constants. (Note that there are various things which can affect exactly how and where something is stored, such as compiler configuration and optimisation.). Personally, I avoid #define except for keywords to make reading my code easier. for the number 255, the binary form is 11111111. I have one, too, but I want it to run an arduino in a project I've not thought of yet! 2 KB and 32 KB respectively for the Uno). They will both generate exactly the same machine code (depending on some compiler optimisations). In this way it acts like a '#define' - since the value is known to the compiler, no storage need be allocated for it. const int ci_max_encoder_clicks = 80 ; One thing is that you test for the symbols existence during compilation if it created with a #define using conditionals Even if you want to remain C compatible (because of technical requirements, because you're kickin' it old school, or because people you work with prefer it that way), you can still use enum and should do so, rather than use #define. so in this case: doesn't matter. By default, these numbers are treated as intbut you can change this with the U and L modifiers (see below). Making statements based on opinion; back them up with references or personal experience. in C++? Integer constants are numbers that are used directly in a sketch, like 123. This is likely why James says they can introduce hard-to-find bugs. Personally I would suggest beginners steer clear of it. How to set a newcommand to be incompressible by justification? How can I use a VPN to access a Russian website that is banned in the EU? #define PI_VALUE 3.14159 Debuggers like Visual Studio's don't let you. For pin number you should not use int as it wastes memory, use one of the byte sized types. If you ask it nicely, it will provide warnings. True, but compiling with the default settings for the IDE is alarmingly quiet, and those are the settings that most newbies use. Also all the compiler options can be modified ( just not without restarting the IDE ). You can't initialize a const with another const. A scope is a region of the program and there are three places where variables can be declared. int *const is a constant pointer to integer This means that the variable being declared is a constant pointer pointing to an integer. This is SO much more complicated than Python With complexity comes power. The maximum positive value of an "int" depends on the compiler. Are you more or less confused now? program memory rather than SRAM) anywhere that it's used. I have been programming professionally since 1978, and could see NO reason to use const instead of define, based on my experience and reading of the documentation. There are, however, times when the fact that a symbolic constant is typeless can be a good thing (e.g., when working with a union). The keyword "const" tells the compiler that a variable (or pointer) can not be modified. You would create a Remote class, and the Remote might have different members such as name, mfr, and power: Then you can access data of it with things like AKB.mfr, AKB.power. Time to switch to UECIDE! you end up with var being 14464 instead of 80000, This ensures that the value is not truncated to 16 bits. For the most basic case, if you're just representing simple data such as an int or char array, there's not an enormous difference (ignoring under the hood differences such as where data is stored, etc..). 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