Table[n^2, {n, 1, 100}] >> file.dat

Directory[]

SetDirectory["/home/user6/sugawa/data"]

?SetDirectory

Table[n^2, {n, 1, 100}] >> file.dat

<< file.dat

Plot[Sin[x] Exp[-x], {x, 0, 2  Pi}]

graph = %

?Save

Save["graph.dat", graph]

graph1 << graph.dat

Show[graph1]

graph >> graph.dat

graph1 = << graph.dat

Show[graph1]

InputForm[graph1]

f[x_] := If[x > 0, x^2, -x]

Plot[f[x], {x, -2, 2}]

Save["user.m", f]