Compilare: user.c: In function ‘main’: user.c:16:5: warning: implicit declaration of function ‘isdigit’ [-Wimplicit-function-declaration] if(isdigit(ch)){ ^ user.c:18:5: warning: implicit declaration of function ‘isalpha’ [-Wimplicit-function-declaration] }else if(isalpha(ch)){ ^ user.c:6:24: warning: unused variable ‘len’ [-Wunused-variable] int B, K, i, result=0, len, digit, base=1; ^ user.c:6:11: warning: unused variable ‘i’ [-Wunused-variable] int B, K, i, result=0, len, digit, base=1; ^ user.c:12:7: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(file1, "%d %d", &B, &K); ^