b=1;
a=b;
b=2;
a

c=1;
d:=c;
c=2;
d

f[x_]=(x^2);
f[3]

y=2;
g[y_]=(y^2);
g[3]

z=2;
h[z_]:=(z^2);
h[3]

x=7

y:=9