Plot[Sin[x],{x,0,4*Pi}]

Plot[Sin[x],{x,-300,300}]

Plot[Sin[x]/x,{x,0,50}]

Plot[{Sin[x]/x,Tan[x]-x},{x,0,50}]

Plot[{Sin[x]/x,Tan[x]-x},{x,0,50},PlotRange->{{0,50},{-0.3,0.3}}]

ListPlot[{{-3,9},{-2,4},{-1,1},{0,0},{1,1},{2,4},{3,9}}]

ListPlot[{{-3,9},{-2,4},{-1,1},{0,0},{1,1},{2,4},{3,9}},Joined->True]

ListPlot[Table[{x,Sin[x]},{x,0,2*Pi,0.1}]]

ListPlot[Table[{x,Sin[x]},{x,0,2*Pi,0.1}],Joined->True]

tent[x_]:=If[x<1/2,2*x,2-2*x]

Plot[tent[tent[tent[x]]],{x,0,1}]
Plot[tent @* tent @* tent @ x,{x,0,1}] 

tent[x_]:=Block[{y},y=If[x<1/2,2*x,2-2*x]; Return[y]]

sum12[from_,to_]:=Block[{s1,s2,i},
 s1=0; s2=0;
 For[i=from,i<=to,i++,
  s1 = s1+i;
  s2=s2+i^2;
 ];
 Return[{s1,s2}]
]

sum12[1,100] 

Sum[i^2,{i,1,100}]

a={10,20,30,40};
a[[1]]=11;
Print[a];

b={{1,2},{3,4}};
b[[1,1]]

(*
ToString[] <==>  ToExpression[]
ToCharacterCode[]
FromCharacterCode[]
b=ReadByteArray[fileName]
b2=Normal[b]; b3=ByteArray[b2]

<<fileName 
or 
Get[fileName]
*)


(* Mobius ring *)
ParametricPlot3D[{Cos[2*t]*(r*Cos[t]+2), Sin[2*t]*(r*Cos[t]+2),r*Sin[t]},
  {r,-1,1},{t,0,Pi}]

(* report 1 by mathematica *)
a=Normal[ReadByteArray["c-text1.txt"]];
b=Mod[a+168,256];
FromCharacterCode[b]