About the "int" data type variable

i looking @ example code , noticed these lines:

code: [select]

// constants won't change. used here
// set pin numbers:
const int ledpin =  13;      // number of led pin

// variables change:
int ledstate = low;             // ledstate used set led
long previousmillis = 0;        // store last time led updated

my question is, if "int" type stores integers, why being used store "low?" why not make compiler error?

later in program use this:

code: [select]

  if(currentmillis - previousmillis > interval) {
     // save last time blinked led
     previousmillis = currentmillis;   

     // if led off turn on , vice-versa:
     if (ledstate == low)
       ledstate = high;
     else
       ledstate = low;

     // set led ledstate of variable:
     digitalwrite(ledpin, ledstate);

so question is, int variable lets store "low" or "high" in it, , not number?

second question wouldn't program better (more memory efficient) change ledstate , do, example:

code: [select]

boolean ledon=true;

thanks!

quote

my question is, if "int" type stores integers, why being used store "low?" why not make compiler error?

because low defined replaced zero.

you better storing in "byte" (uint8_t) variable.

what see:

code: [select]

digitalwrite (pin, low);

what compiler sees:

code: [select]

digitalwrite (pin, 0);

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