#include void make_lower(char a[], char b[]); typedef struct login { char a[10]; char b[10]; }LOGIN; int main() { LOGIN arr; printf("ID?"); gets(arr.a); printf("PASSWORD?"); gets(arr.b); make_lower(arr.a, arr.b); return 0; } void make_lower(char a[], char b[]) { int a1, b1; a1 = strlen(a); b1 = strlen(b); for (int i = 0; i < a1; i++) { if (islower(a[i])==0) a[i] = tolower(a[i]); } printf("ID: ")..