Tic Tac Toe Game | Project in C Programming Language

/*
C Program for Tic Tac Toe Game
*/

#include <stdio.h>
#include <stdlib.h>

//print matrix
void printMatrix(char val);
 
//update value in matrix
void insertValue(int i,int j,unsigned char user);
 
//check matrix is full or not
unsigned char isFull(void);
 
//check game is completed or not.
unsigned char isOver(void);

unsigned char mat[3][3]={'_','_','_','_','_','_','_','_','_'};
 
unsigned char usertern=0;
 
unsigned char onlyOnce=0;

int main()
{
unsigned char user1[30],user2[30],winner;
 
int ival,jval;

printf("\nEnter name of U1 :");
 
gets(user1);
 
fflush(stdin);


printf("Enter name of U2 :");
 
gets(user2);
 
fflush(stdin);

again:
 
system("clear");
 
printf("\n\n\n\n");
 
if(!onlyOnce) {

printMatrix(0); onlyOnce=1;}
 
else { printMatrix(1);}
 
winner=isOver();

if(winner)
{
printf("\n *** Congrats... %s ,\n You have won the game . !!!!",((winner=='X')?user1:user2));
 
goto end;
}

if(!isFull()) {printf("\n *** Game Over ."); goto end;}

repeat:
 
fflush(stdin);

printf("\n *** %s , Enter value (00-22) seperated by space :",(usertern==0x00?user1:user2));
 
scanf("%d%d",&ival,&jval);
 
if( (ival>2 || ival<0) || (jval>2 || jval<0)) {
 
printf("\n *** ERROR : Invalid index, try again !!!");
 
goto repeat;
}
 
if(mat[ival][jval]!='_'){

printf("\n *** ERROR : Already filled,try again !!!"); 

goto repeat;

}
 
insertValue(ival,jval,usertern);
 
usertern=!usertern;
 
goto again;

end:
printf("\n");return 0;
}

void printMatrix(char val)
{
unsigned char i,j;
 
if(!val){

for(i=0;i<3;i++){
 
for(j=0;j<3;j++){printf("[%3c ] ",mat[i][j]);} printf("\n");
}

return;
}
for(i=0;i<3;i++){
 
printf("\t\t\t");
 
for(j=0;j<3;j++){printf("[%3c ] ",mat[i][j]);} printf("\n");
}
return;
}

void insertValue(int i,int j,unsigned char user){

mat[i][j]=((user==0x00)?'X':'O');
}

unsigned char isFull(void){
 
unsigned char i,j,count=0;;
 
for(i=0;i<3;i++)
 
for(j=0;j<3;j++){ 

if(mat[i][j]=='_') ++count; 

}
 
return count;
}

unsigned char isOver(void){

unsigned char i,j,user;
 
unsigned char storeChar=0,flag;
 
int sum=0;
 
// case 1
flag=0;
 
for(i=0;i<3;i++)
{ 
sum=0;
 
for(j=0;j<3;j++)
{
if(mat[i][j]=='_') break;
 
sum+=mat[i][j];
 
storeChar=mat[i][j];
}

if(sum==237||sum==264){return storeChar;}
}

// case 2
for(i=0;i<3;i++)
 
{ 
sum=0;
for(j=0;j<3;j++)
{
 
if(mat[j][i]=='_') break;
 
sum+=mat[j][i];
 
storeChar=mat[j][i];
}

if(sum==237||sum==264){return storeChar;}
 
}

// case 3
for(i=0;i<3;i++)
{
sum=0;
 
for(j=0;j<3;j++)
{
 
if(i==j){
 
if(mat[i][j]=='_') break;
 
sum+=mat[i][j];
 
storeChar=mat[i][j];
 
}
}
 
if(sum==237||sum==264){ return storeChar;}
 
}

return 0;

}