Compilare: user.c: In function ‘cmmdc’: user.c:13:5: warning: implicit declaration of function ‘abs’ [-Wimplicit-function-declaration] return abs(a); ^ user.c: At top level: user.c:16:1: warning: return type defaults to ‘int’ [enabled by default] main() ^ user.c: In function ‘main’: user.c:20:11: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f,"%d%d",&a,&b); ^