Tic-tac-toe or Xs and Os is a paper-and-pencil game for two players who take turns marking the spaces in a three-by-three grid with X or O. The player who succeeds in placing three of their marks in a horizontal, vertical, or diagonal row is the winner. It is a solved game, with a forced draw assuming best play from both players.
Gameplay :
The goal of tic-tac-toe is to be the first player to get three in a row on a 3-by-3 grid or four in a row in a 4-by-4 grid.
To start, one player draws a board, creating a grid of squares, usually 3-by-3 or 4-by-4.
In a 3-by-3 grid game, the player who is playing "X" always goes first. Players alternate placing Xs and Os on the board until either player has three in a row, horizontally, vertically, or diagonally or until all squares on the grid are filled. If a player is able to draw three Xs or three Os in a row, then that player wins. If all squares are filled and neither player has made a complete row of Xs or Os, then the game is a draw.
One of the game's best strategies involves creating a "fork," which is placing your mark in such a way that you have the opportunity to win two ways on your next turn. Your opponent can only block one, thereby, you can win after that.
The gameplay is the same if you are playing on a 4-by-4 grid. The "X" player goes first. And, players alternate placing Xs and Os on the board until a row is completed horizontally, vertically, or diagonally, or all 16 squares are filled. If all 16 squares are filled and neither player has four in a row, the game is a draw.
History :
Games played on three-in-a-row boards can be traced back to ancient Egypt, where such game boards have been found on roofing tiles dating from around 1300 BC.
An early variation of tic-tac-toe was played in the Roman Empire, around the first century BC. It was called terni lapilli (three pebbles at a time) and instead of having any number of pieces, each player had only three; thus, they had to move them around to empty spaces to keep playing. The game's grid markings have been found chalked all over Rome. Another closely related ancient game is three men's morris which is also played on a simple grid and requires three pieces in a row to finish, and Picaria, a game of the Puebloans.
The different names of the game are more recent. The first print reference to "noughts and crosses" (nought being an alternative word for 'zero'), the British name, appeared in 1858, in an issue of Notes and Queries. The first print reference to a game called "tick-tack-toe" occurred in 1884, but referred to "a children's game played on a slate, consisting of trying with the eyes shut to bring the pencil down on one of the numbers of a set, the number hit being scored".[This quote needs a citation] "Tic-tac-toe" may also derive from "tick-tack", the name of an old version of backgammon first described in 1558. The US renaming of "noughts and crosses" to "tic-tac-toe" occurred in the 20th century.
In 1952, OXO (or Noughts and Crosses), developed by British computer scientist Sandy Douglas for the EDSAC computer at the University of Cambridge, became one of the first known video games. The computer player could play perfect games of tic-tac-toe against a human opponent.
In 1975, tic-tac-toe was also used by MIT students to demonstrate the computational power of Tinkertoy elements. The Tinkertoy computer, made out of (almost) only Tinkertoys, is able to play tic-tac-toe perfectly. It is currently on display at the Museum of Science, Boston.