Error(s):

source_file.c:7:1: error: unknown type name ‘bool’
 bool EsNum(char *frase)
 ^
source_file.c: In function ‘EsNum’:
source_file.c:11:12: warning: implicit declaration of function ‘isdigit’ [-Wimplicit-function-declaration]
         if(isdigit(frase[i])){}else
            ^
source_file.c:12:16: error: ‘false’ undeclared (first use in this function)
         return false;
                ^
source_file.c:12:16: note: each undeclared identifier is reported only once for each function it appears in
source_file.c:14:12: error: ‘true’ undeclared (first use in this function)
     return true;
            ^
source_file.c: At top level:
source_file.c:17:29: error: unknown type name ‘FILE’
 void FiltrarPolidivisibles (FILE *entrada, FILE **salida) 
                             ^
source_file.c:17:44: error: unknown type name ‘FILE’
 void FiltrarPolidivisibles (FILE *entrada, FILE **salida) 
                                            ^
source_file.c: In function ‘EsNum’:
source_file.c:15:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^