Notice: This page requires JavaScript to function properly.
Please enable JavaScript in your browser settings or update your browser.Lære Cancel Macro | Macros
C Preprocessing

Sveip for å vise menyen

book
Cancel Macro

The #undef directive in the C programming language is used to undefine a previously declared macro created using the #define directive.

python

This allows you to remove a macro from the current scope so that its name can be redefined or no longer used in your program.

Macros are global: Macros operate at the preprocessor level, and their scope extends to the entire file where they are defined. Once redefined, the new value will be used wherever that macro appears later in the code.

c

main

copy

              
1234567891011

            
#include <stdio.h>
#define MAX 100

int main() 
{
    printf("MAX = %d\n", MAX); // MAX = 100
    #undef MAX                 // remove macros MAX
    #define MAX 200            // define new macros MAX
    printf("MAX = %d\n", MAX); // MAX = 200
    return 0;
}
Switch to desktopBytt til skrivebordet for virkelighetspraksisFortsett der du er med et av alternativene nedenfor
Alt var klart?

Hvordan kan vi forbedre det?

Takk for tilbakemeldingene dine!

Seksjon 2. Kapittel 4

Spør AI

expand
ChatGPT

Spør om hva du vil, eller prøv ett av de foreslåtte spørsmålene for å starte chatten vår

book
Cancel Macro

The #undef directive in the C programming language is used to undefine a previously declared macro created using the #define directive.

python

This allows you to remove a macro from the current scope so that its name can be redefined or no longer used in your program.

Macros are global: Macros operate at the preprocessor level, and their scope extends to the entire file where they are defined. Once redefined, the new value will be used wherever that macro appears later in the code.

c

main

copy

              
1234567891011

            
#include <stdio.h>
#define MAX 100

int main() 
{
    printf("MAX = %d\n", MAX); // MAX = 100
    #undef MAX                 // remove macros MAX
    #define MAX 200            // define new macros MAX
    printf("MAX = %d\n", MAX); // MAX = 200
    return 0;
}
Switch to desktopBytt til skrivebordet for virkelighetspraksisFortsett der du er med et av alternativene nedenfor
Alt var klart?

Hvordan kan vi forbedre det?

Takk for tilbakemeldingene dine!

Seksjon 2. Kapittel 4
Switch to desktopBytt til skrivebordet for virkelighetspraksisFortsett der du er med et av alternativene nedenfor
Vi beklager at noe gikk galt. Hva skjedde?
some-alt