I'm learning C and decided to write my first major project in C. I was bored and wanted to play blackjack so I decided to create my own game. My program starts the user off with 500 credits and continues playing until the user runs out of credits or quits, at which point they can start again by typing `play`. The main input components are `hit`, `stand`, `help`, `bet $`, and `quit`.

I've also added a lot of code to handle special cases that I've encountered while playing the game (for example if the player was dealt a 10-value card and an Ace, it automatically gives the user a Blackjack instead of prompting the user to decide what value to get from the Ace card).

I'm certain that there are many things I could do to improve the structure and efficiency of my code.

```
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define CARDS 52

int balance;
int pot;
int deck[52];
int sdeck[52];

void play();
void turn();
int hit(int *val);
char *cface(int v);
char *csuit(int v);
int cval(int v);
void bet();
void dealer();
void result();
void initdeck();
void shuffle();
void checkAce(int v1, int v2, int *a1);
void quit();

int main(){ 
    printf("Welcome to my BlackJack Simulator! Below are the basic rules:\n- Beat the dealer's  hand without going over 21.\n- Face cards are worth 10, Aces are worth 1 or 11, whichever makes a better hand.\n- Each player starts with two cards, and one of the dealer's cards is hidden until the end.\n- Type 'hit' to ask for another card. Type 'stand' to hold your total and end your turn.\n- If you go over 21 you bust, and the dealer wins regardless of his hand.\n- If you are dealt 21 from the start (Ace & 10), you got a blackjack. If you get a blackjack, you win 1.5 times the amount of your bet automatically, unless the dealer also gets a blackjack, in which case it is a push.\n- Remember: Type 'hit' to get another card, and 'stand' to hold. At the beginning of the round, type 'bet' followed by the quantity you want to bet (i.e. 'bet 50').\nType 'play' to begin. At any time, you may type 'help' to get a list of valid commands.\n");
    char input[6];
    scanf("%5s", input);
    while(strcmp(input, "quit") != 0){
        while(strcmp(input, "play") != 0){
            if(strcmp(input, "help") == 0)
                printf("Type 'play' to begin the game.\n");
            else if(strcmp(input, "quit")==0){
                quit();
                printf("Enter 'play' to start the game.\n");
            }else
                printf("Invalid command, type 'play' to begin.\n");
            scanf("%s", input);
        }       
        play();
        scanf("%5s", input);
    }
}

void play(){
    printf("Lets start you off with 500 credits.\n");
    balance = 500;
    while(balance>0){
        bet();
        initdeck();
        shuffle();
        turn();
    }
    printf("Sorry, it looks like you lost! Type 'play' to play another game.\n");
}

void turn(){
    int inc=0;

    int d1 = hit(&inc);
    char *cn1 = csuit(d1);
    char *cf1 = cface(d1);
    int cv1 = cval(d1);

    printf("You got a %s of %s worth %d, and ", cf1, cn1, cv1);

    int d2 = hit(&inc);
    char *cn2 = csuit(d2);
    char *cf2 = cface(d2);
    int cv2 = cval(d2);

    printf("a %s of %s worth %d.\n", cf2, cn2, cv2);

    int d3 = hit(&inc);
    char *cn3 = csuit(d3);
    char *cf3 = cface(d3);
    int cv3 = cval(d3);

    printf("The dealer's face up card is a %s of %s worth %d.\n", cf3, cn3, cv3);

    int d4 = hit(&inc);
    char *cn4 = csuit(d4);
    char *cf4 = cface(d4);
    int cv4 = cval(d4);

    int ptotal = cv1 + cv2;
    int dtotal = cv3;

    checkAce(cv1, cv2, &ptotal);

    printf("You have a total of %d points, and the dealer has %d.\n", ptotal, dtotal);  

    if(ptotal == 21){
        printf("Congrats! You got a blackjack!! Your payout is 2-to-1, %d.\n", (int)(pot*2));
        balance += (pot*2);
    }else{
        char input[6];
        scanf("%5s", input);
        while(strcmp(input,"stand")!=0){
            if(strcmp(input,"hit") == 0){
                int val = hit(&inc);
                char *ns = csuit(val);
                char *nf = cface(val);
                int nv = cval(val);
                ptotal += nv;
                printf("You got a %s of %s worth %d.\n", nf, ns, nv);
                if(ptotal < 21){
                    if(nv==1){
                        if(ptotal+10 == 21){
                            ptotal += 10;
                            printf("Congrats! You got 21! Payout is 2-to-1.\n");
                            balance += (pot*2);                         
                            break;
                        }else{
                            int input;
                            printf("You've got an ace. Choose whether you want to make it count as 1 or 11.\n");
                            scanf("%d",&input);
                            if(input == 11)
                                ptotal += 10;
                        }
                    }
                }else if(ptotal == 21){
                    printf("Congrats! You got 21!\n");
                    break;
                }else{
                    printf("Oh no, you've busted with %d. Try Again!\n", ptotal);
                    break;
                }
            }else if(strcmp(input,"help")==0)
                printf("Type 'hit' to be dealt another card. Type 'stand' to hold.\n");
            else if(strcmp(input, "quit")==0){
                quit();
                printf("Enter 'hit' or 'stand'.\n");
            }else
                printf("Invalid command, try again.\n");
            printf("Your new total is %d.\n", ptotal);
            scanf("%5s", input);
        }
    }

    if(ptotal < 21){

        printf("The dealer's flips a %s of %s worth %d.\n", cf4, cn4, cv4);
        dtotal += cv4;
        if(cv4 == 1){
            if(dtotal+11 < 21)
                dtotal += 10;
        }

        if(dtotal >= 16){
            printf("The dealer stands with %d.\n", dtotal);
        }

        while(dtotal < 16){
            int val = hit(&inc);
            char *ns = csuit(val);
            char *nf = cface(val);
            int nv = cval(val);
            dtotal += nv;
            printf("The dealer got a %s of %s worth %d.\n", nf, ns, nv);
            if(dtotal < 16){
                if(nv==1){
                    if(dtotal+11<21)
                        dtotal += 10;
                }
            }else if(dtotal == 21){
                printf("The dealer just got 21.\n");
                break;
            }else if(dtotal > 21){
                printf("The dealer busted with %d! You win!\n", dtotal);
                break;
            }else{
                printf("The dealer stands with %d.\n", dtotal);
                break;
            }
            printf("The dealer's new total is %d.\n", dtotal);
        }
        if(dtotal<ptotal){
            printf("You beat the dealer! Your payout is %d.\n", (int)(pot*1.5)); 
            balance += (pot*1.5);
        }else if(dtotal==ptotal){
            printf("Its a tie! Push pot, 1-to-1 payout of %d.\n", pot);
            balance += pot;
        }else if(dtotal>ptotal && dtotal <= 21){
            printf("Oh no! Looks like the dealer won. Try again!\n");   
        }else{
            printf("You beat the dealer! Your payout is %d.\n", (int)(pot*1.5)); 
            balance += (pot*1.5);
        }
    }
    if(balance > 0)
        printf("Your new balance is %d.\n", balance);
}

void checkAce(int v1, int v2, int *a1){
    if(v1 == 1 || v2 == 1){
        int input;
        if(v1 == 1 && v2 == 1){
            v1 = 11;
            v2 = 1;
            *a1 = 12;
            printf("Since you got 2 Aces, we set one to be worth 11 and the other to be worth 1.\n");
        }else if(v1 == 1 || v2 == 1){
            if(v1+10+v2 == 21)
                *a1 == 21;
            else{
                printf("You've got an ace. Choose whether you want to make it count as 1 or 11.\n");
                scanf("%d",&input);
                if(input == 11)
                    *a1 += 10;
            }
        }
    }
}

int cval(int v){
    int a;
    if(((v%13)+1)<10)
        a = v%13+1;
    else 
        a = 10;
    return a;
}

char *csuit(int v){
    v = v%4;
    switch(v){
        case 0 :
            return "Hearts";
        case 1 :
            return "Clubs";
        case 2 :
            return "Diamonds";
        case 3 :
            return "Spades";
    }
}

char *cface(int v){
    v = v%13+1;
    char *output;
    switch(v){
        case 1 :
            output = "Ace";
            break;
        case 2 :
            output = "Two";
            break;
        case 3 :
            output = "Three";
            break;
        case 4 :
            output = "Four";
            break;
        case 5 :
            output = "Five";
            break;
        case 6 :
            output = "Six";
            break;
        case 7 :
            output = "Seven";
            break;
        case 8 :
            output = "Eight";
            break;
        case 9 :
            output = "Nine";
            break;
        case 10 :
            output = "Ten";
            break;
        case 11 :
            output = "Jack";
            break;
        case 12 :
            output = "Queen";
            break;
        case 13 :
            output = "King";
    }
    return output;
}

void quit(){
    printf("Are you sure you want to quit? Type 'y' or 'n'.\n");
    char input[6];
    scanf("%s",input);
    if(strcmp(input,"y")==0)
        exit(0);
    else 
        printf("Quit cancelled.\n");
}

int hit(int *i){
    int a = sdeck[*i];
    *i = *i + 1;
    return a;
}

void bet(){
    char input[6];
    int val;
    printf("Enter an amount you would like to bet.\n");
    scanf("%5s", input);
    while(strcmp(input, "bet") != 0){
        if(strcmp(input,"help") == 0)
            printf("Type 'bet' followed by a bet amount. For example, you could type 'bet 50'.\n"); 
        else if(strcmp(input,"quit")==0){
            quit();
            printf("Enter a bet amount.\n");
        }else
            printf("You've entered an invalid command. Type 'help' for a list of valid commands.\n");
        scanf("%5s", input);
    }
    scanf("%d", &val);
    while(val > balance || (val < 10  && val > 0) || val <=0){
        if(val > balance)
            printf("You cannot bet more than your balance. Your balance is: %d.\n", balance);
        else if(val <= 0)
            printf("You must make a bet. Enter a valid bet amount.\n");
        else
            printf("Invalid entry. Try again.\n");
        scanf("%d", &val);
    }
    balance -= val;
    printf("You've made a bet of %d. Good luck!\n", val);
    pot = val;      
}

void initdeck(){
    int i=0;
    for(i;i<52;i++){
        deck[i] = i+1;  
    }
}

void shuffle(){
    srand(time(NULL));
    int i=0;
    for(i;i<52;i++){
        sdeck[i] = deck[i];
    }
    i=0;
    for(i=CARDS-1;i>0;i--){
        int j = rand()%(i+1);
        int n = sdeck[i];
        sdeck[i] = sdeck[j];
        sdeck[j] = n;
    }
}

```