This illustration shows the board after you have invoked the F5 function, either by hitting the function key or clicking on the F5 icon on the Sudoku board. In a sense, this is a variation of the F1 function, since it displays all singletones on the board. Notice that a single number appears on the board in the position coresponding to its place in a 3x3 array which looks like when completely filled.
This is how the board looks after you have clicked on the function key F6 on the keyboard...OR...you have clicked on the F6 icon on the Sudoku board at the far right. Note that only squares in which it is possible to place exactly two numbers are displayed with small numbers in them. This will help you make educated guesses as to how to proceed when all singletons have been located.
If any of these three functions is evoked while another of them is in play, it will replace that function, turning it off as it goes into play. These functions are useful in identifying possibilities at any stage of the solving of the Sudoku puzzle.
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This illustration shows the board after you have invoked the F5 function, either by hitting the function key or clicking on the F5 icon on the Sudoku board. In a sense, this is a variation of the F1 function, since it displays all singletones on the board. Notice that a single number appears on the board in the position coresponding to its place in a 3x3 array which looks like 
when completely filled.
This is how the board looks after you have clicked on the function key F6 on the keyboard...OR...you have clicked on the F6 icon on the Sudoku board at the far right. Note that only squares in which it is possible to place exactly two numbers are displayed with small numbers in them. This will help you make educated guesses as to how to proceed when all singletons have been located.
Here is a display that shows ALL possible numbers that might be placed in an empty cell at this time. If you invoke this function while you are filling in the numbers in an empty board...using the