# How do I declare global constants and local constants? [duplicate]

Many times I have a Mathematica code like this

v[t_] = {Subscript[v, 1][t], Subscript[v, 2][t], Subscript[v, 3][t]}
B = {Subscript[b, 1], Subscript[b, 2], Subscript[b, 3]}
elc = {Subscript[e, 1], Subscript[e, 2], Subscript[e, 3]}
A = q/c {{0, Subscript[b, 3], -Subscript[b, 2]}, {-Subscript[b, 3], 0,
Subscript[b, 1]}, {Subscript[b, 2], -Subscript[b, 1], 0}}

system = v'[t] == 1/m ( A.v[t]+q elc)
sol = DSolve[system, {Subscript[v, 1], Subscript[v, 2], Subscript[v, 3]}, t]


Note $q,c,B,elc.m$ are all constants (or their components are). I would like to know how to declare symbolic constants globally and locally (such as when solving a ode). As I would like to both be able to declare all my constants at once and locally. (I believe that the above linear ode system gives a very complex answer without declaring constants, if I am wrong please correct me and also answer my question).