<membership expression>

  ┌◄──────────┬── AND ─┬───────────┐
  │           ├◄─ OR ──┤           │
  │           ├◄─ ! ───┤           │
  │           ├◄─ IMP ─┤           │
  │           └◄─ EQV ─┘           │
──┴─┬───────┬─<membership primary>─┴───────────────────────────────────┤
    └─ NOT ─┘

<membership primary>

──┬─<string literal>──────────────────┬────────────────────────────────┤
  ├─<truth set identifier>────────────┤
  ├─ ( ──<membership expression>── ) ─┤
  ├─ ALPHA ───────────────────────────┤
  ├─ ALPHA7 ──────────────────────────┤
  └─ ALPHA8 ──────────────────────────┘

All membership primaries of a membership expression must be of the same character size (4-bit, 7-bit, or 8-bit); this character size determines the type of the truth set. The character size of a string literal is determined by the maximum character size indicated by its component string codes. For more information, refer to String Literal.

A membership expression is evaluated according to the normal rules of precedence for Boolean operators. This precedence is described under Boolean Expressions.

ALPHA, ALPHA7, and ALPHA8 are intrinsic truth sets defined as follows:

If a default character type is not explicitly specified by the compiler control option ASCII, then the default character type is EBCDIC, and ALPHA is the same as ALPHA8. If the ASCII compiler control option is TRUE, then ALPHA is the same as ALPHA7.