Figure 8 shows stencil diagrams for 4 schemes with
and different time centering:
with different time-centering: FTCS, time-centered implicit, BTCS, CTCS (leapfrog).
In implicit schemes each value at the new time level typically depends on
all values at the old level:
The full domain of dependence is larger than the direct domain of dependence.
FT: forward-time (explicit)
time-centered implicit: (implicit)
BT: backward-time (fully
CT, Leapfrog: center-time (explicit, uses 3 time planes)