The program checks every character in the string. If the character is a digit from 0 to 9, it increases the count for that digit. At the end, it prints how many times each digit appeared.
#includeint main() { const char* str = "6480 89839 041710 90216"; int count[10] = {0}; int i = 0; while (str[i] != '\0') { if (str[i] >= '0' && str[i] <= '9') { count[str[i] - '0']++; } i++; } for (i = 0; i < 10; i++) { printf("%d: %d\n", i, count[i]); } return 0; }