flowchart - What does the zig-zag arrow in the System Flows Chart indicate? -

i have following situation required depicted systems flow chart:

my attempt @ drawing these diagrams figure out following 4 things:

1) input= sales transaction

2) process= verification of credit card

3) output= reciept

4) stored data= prices, product , transaction files

how involve central computer?

the model answer problem is:

i've looked several legends describe common symbols used in system flowcharts, i've never come across circle , zig-zagged lines. know proper definitions these 2 symbols. per knowledge, can't represent input, document or storage system. they?

lastly, please share resource learning , practising system flow chart diagrams or maybe heuristic 1 can use solve such problems?

so zig-zag line communication link, found there (page 3), maybe depends on tool working with.

that zig-zag symbol represents transmission of data 1 location via communication lines.

also circle/elipse stands beginning, end, or point of interruption in process or program. used indicate external party.

in case external party.