Compilare: user.c: In function ‘main’: user.c:26:13: warning: implicit declaration of function ‘exit’ [-Wimplicit-function-declaration] exit(1); ^ user.c:26:13: warning: incompatible implicit declaration of built-in function ‘exit’ [enabled by default] user.c:33:9: warning: format ‘%s’ expects argument of type ‘char *’, but argument 3 has type ‘char (*)[20]’ [-Wformat=] fscanf(f,"%s",&mat[i]); ^ user.c:119:17: warning: incompatible implicit declaration of built-in function ‘exit’ [enabled by default] exit(1); ^ user.c:19:9: warning: unused variable ‘a’ [-Wunused-variable] int a=1; ^