Some basic concepts
The subject of our interest is a program written in MQL4. Before we start a detailed presentation of the rules of writing programs, it is necessary to describe the basic concepts that characterize a program and its interrelations with the information environment. The MetaTrader 4 Client Terminal works with an online connection. The situation on financial markets changes continually, which affects symbol charts in the client terminal. Ticks provide the client terminal with information about price changes on the market.