Program Unit

A program unit is a group of ALGOL constructs that can be compiled as a whole. The following diagram shows the elements that can be included in an ALGOL program.

<program unit>

──┬─<block>──────────────┬─.  ─────────────────────┬───────────────────┤
  ├─<compound statement>─┤                         │
  ├─<level 2 procedure>──┘                         │
  │                 ┌◄───────── ; ─────────┐       │
  ├───────────────┬─┴─<separate procedure>─┴─┬─ . ─┤
  └─<global part>─┘                          └─ ; ─┘

<block>

── BEGIN ──<declaration list>──; ──<statement list>── END ────────────┤

<declaration list>

  ┌◄────── ; ─────┐
──┴─<declaration>─┴────────────────────────────────────────────────────┤

<statement list>

  ┌◄───── ; ────┐
──┴─<statement>─┴──────────────────────────────────────────────────────┤

<compound statement>

── BEGIN ──<statement list>── END ─────────────────────────────────────┤

<level 2 procedure>

──<procedure declaration>──────────────────────────────────────────────┤

<global part>

── [ ──<declaration list>── ] ─────────────────────────────────────────┤

<separate procedure>

──<procedure declaration>──────────────────────────────────────────────┤
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