What is the MQL4 variable/term/predefined variable used to reference a currency pair by name on a trading platform?

 

To reference the currency pair within which you have found candles, trades, patterns etc. with specified conditions given in your program logic are occuring, what is the MQL4 term that you would reference? i.e. how do you reference the field 'eurusd', 'usdjpy', 'gbpusd' within an MQL4 program?

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