plot with errorbars using gnuplot

plot "tt" using 1:5:6  -t "label1" with errorbars, "tt1" using 1:5:6  -t "label2" with errorbars
---- using 1:5:6 means: to use the 1th, 5th and 6th column of data in the file tt and tt1
---- column1 is the x, column 5 for y, and column 6 for error bars