AT&T 6300 Programmer's Manual page 259

Example 1
FIELD
Statement
Do not use a FIELDed variable name in an
input statement or to the left of the equal sign
in an assignment statement. Once a variable
name is FIELDed, it points to the correct place
in the random file buffer. If a subsequent
INPUT or LET statement with that variable
name on the left side of the equal sign is
executed, the variable no longer refers to the
random file buffer, but to the variables stored
in string space.
If previously defined in a FIELD statement, a
variable name may be inserted to the right of
the equal sign in an assignment statement.
10 FIELD 1,20 AS NS,10 AS 105,40 AS ADDS
Allocates the first 20 positions (bytes) in the
random file buffer to the string variable N$,
the next 10 positions to ID$, and the next 40
positions to ADD$. FIELD does NOT place
any data in the random file buffer. (See also
"GET" and "LSET/RSET" in this chapter.)
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