Tandy 1000 Basic Reference Manual page 108

ChaDter 10 I
BASIC Kevwords
CALLS
Statement
CALLS variables [(parameter list)]
Transfers program control to a routine written in MS'" -FOR-
TRAN. CALLS works just like the CALL statement, except that
CALLS passes arguments as segmented addresses.
CALLS uses the address given in most recently executed
DEF
SEG statement to locate the routine being called.
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