Terminology.

  1. In what follows, the symbols

    ID

    ,

    INTEGER

    ,

    FLOATING$\displaystyle \_$ POINT

    ,

    BOOLEAN

    , and

    STRING

    refer to the terms identifier and integer, floating point number, Boolean, and string constants, which have been specified above. Any other symbol in capital letters is explained in the grammar.

  2. A statement enclosed in double quotes is an extra-grammatical explanation.

  3. Spaces are not allowed within any of the character pairs listed in the section on Characters and Keywords, nor within an

    ID

    ,

    INTEGER

    constant,

    FLOATING$\displaystyle \_$ POINT

    constant, or keyword. Spaces are required between keywords,

    ID

    s,

    INTEGER

    constants, and

    FLOATING$\displaystyle \_$ POINT

    constants.

  4. ISETL treats carriage returns and tabs as spaces. Any input can be spread across lines without changing the meaning, and ISETL will not consider it to be complete until a semicolon ``

    ;

    '' is entered. The only exceptions to this are the

    !include

    input, which is ended with a carriage return, and the fact that a quoted string cannot be typed on more than one line.