C++ Functions output error

Question

I am trying to make a program to play a card game. The goal is to make this by only using functions, and the *main()* function will remain empty other than calling the other functions. I have done this previously without the use of user-defined functions, and it worked flawlessly. I am getting weird outputs this time, any help would be greatly appreciated.

https://www.onlinegdb.com/fork/HyPbh_Dhz

Answer 1

.cpp: In function ‘void drawCards(short unsigned int&, char&, short unsigned int&, char&)’:
1.cpp:85:19: error: ‘srand’ was not declared in this scope
    srand(sequence1);
                   ^
1.cpp:86:29: error: ‘rand’ was not declared in this scope
    randomnumber1 = 3 + rand() % 4;
                             ^
1.cpp: In function ‘bool continueBattle()’:
1.cpp:272:9: error: ‘exit’ was not declared in this scope
   exit(0);