Plotting a function discontinuous at one point
Without having to manually look:
f[x_] := If[x != 1, 1, 0]
g[x_] := Floor[x]/2
Plot[{f[x], g[x]}, {x, 0, 5}, ExclusionsStyle -> {Dotted, Directive[Black, AbsolutePointSize[5]]}]
Comment
Here is a workaround,
f[x_] := If[x != 1, 1, 0]
fdata = Table[{x, f[x]}, {x, 0, 2, 0.001}];
plot = ListPlot[fdata, Joined -> True]
Use Exclusion as plot option:
Plot[1, {x, 0, 2}, Exclusions -> {1},ExclusionsStyle -> {PointSize -> 0.1,Red}, MaxRecursion -> 4,PlotPoints -> 100]