Simulate Tic Tac Toe game using C language

Question

I made a Tic Tac Toe game using C. Here two players, player1 and player2, can participate and play. Please rate my code and suggest improvements.

#include<stdio.h>
#include<conio.h>
void board(char t[]);
int cheak(char T[]);
void main()
{
int i=0,n,r=100,p=1;
char TOT[9]={'1','2','3','4','5','6','7','8','9'};
char a='X';
for(;i<9;i++)
 {
 clrscr();
 board(TOT);
 printf("\n\n\n Player1=X\nPlayer2=O");
 printf(" \n player %d tern:-",p);
 printf("\nEnter number");
 scanf("%d",&n);
 TOT[n-1]=a;
 if(a=='X')
 {
 a='O';
 }
 else
 {
 a='X';
 }
 r=cheak(TOT);
 if(r==1)
 {
 clrscr();
 board(TOT);
 printf("\nPlayer 1 win");
 break;
 }
 if(r==2)
 {
 clrscr();
 board(TOT);
 printf("\nPlayer 2 win");
 break;
 }
 if(p==1)
 {
 p=2;
 }
 else
 {
 p=1;
 }
 if(i==8)
 {
 clrscr();
 board(TOT);
 printf("\n\nMatch Draw");
 break;
 }
 }
getch();
}
void board(char t[])
{
printf("_________________");
printf("\n|| %c || %c || %c ||",t[0],t[1],t[2]);
printf("\n|---------------|");
printf("\n|| %c || %c || %c ||",t[3],t[4],t[5]);
printf("\n|---------------|");
printf("\n|| %c || %c || %c ||",t[6],t[7],t[8]);
printf("\n|---------------|");
}
int cheak(char T[])
{
int i=0,n=0;
for(;n<3;n++)
 {
 if(T[i]=='X'&&T[i+1]=='X'&&T[i+2]=='X')
 {
 return 1;
 }
 i=i+3;
 } 
i=0;
for(n=0;n<3;n++)
 {
 if(T[i]=='X'&&T[i+3]=='X'&&T[i+6]=='X')
 {
 return 1;
 }
 i++;
 }
if(T[0]=='X'&&T[4]=='X'&&T[8]=='X')
 {
 return 1;
 }
if(T[2]=='X'&&T[4]=='X'&&T[6]=='X')
 {
 return 1;
 }
i=0;
for(n=0;n<3;n++)
 {
 if(T[i]=='O'&&T[i+1]=='O'&&T[i+2]=='O')
 {
 return 2;
 }
 i=i+3;
 }
i=0;
n=0;
for(;n<3;n++)
 {
 if(T[i]=='O'&&T[i+3]=='O'&&T[i+6]=='O')
 {
 return 2;
 }
 i++;
 }
if(T[0]=='O'&&T[4]=='0'&&T[8]=='O')
 {
 return 2;
 }
if(T[2]=='O'&&T[4]=='O'&&T[6]=='O')
 {
 return 2;
 }
return 0;
}

Answer 1

void main() is not portable

Although it "works" in a lot of cases, the only two portable definitions of main are:

int main(void)

and

int main(int argc, char **argv)

Error checking

You don't check the return value of scanf.

This would be better:

if(scanf("%d", &n) != 1)
{
 fputs("Error; enter a number.", stderr);
 return EXIT_FAILURE; /* entering a letter will cause infinite loop so error out here */
}

Note that EXIT_FAILURE requires stdlib.h to be included.

Out-of-bounds write

If a user enters a 0 or a number greater than 9 in the scanf mentioned above, this line will write outside of the array bounds:

 TOT[n-1]=a;

This can cause a segmentation fault.

Spelling

There are a couple spelling errors in this code:

cheak -> check
tern -> turn

Formatting

There are a few issues with formatting here; first of all, each line in a function should be indented by at least 4 spaces. In addition, you should put spaces after commas in function calls, and around most (if not all) operators.

Portability

Although clrscr and getch work with Windows and DOS, I would suggest simply removing clrscr and replacing getch with getchar. This makes your code portable to the point where it can run on most other systems.

Non-descriptive variable names

At first glance, I don't know what t, T, TOT, a, i, n, r, or p are for. The variable names should describe what they contain.

Spacing

Although the board is nice, the prompt to the user isn't. I would suggest something like this:

 printf("\n\n\nPlayer 1 = X\nPlayer 2 = O");
 printf("\nPlayer %d's turn.",p);
 printf("\n\nEnter a number: ");

...

 if(r == 1 || r == 2)
 {
 board(TOT);
 printf("\nPlayer %d wins!", r);
 break;
 }

Misc.

p is already 1 here. You don't need to set it again:

 else
 {
 p=1;
 }