IEC (International Electrotechnical Commission) is a worldwide organization for standardization including all national electronic commissions. The IEC norm describes programmable controls and consists of eight parts:

    • part 1: general information
    • part 2: equipment demands and tests
    • part 3: programming languages
    • part 4: user guide lines
    • part 5: communication areas
    • part 6: reserved
    • part 7: Fuzzy-Controller programming
    • part 8: guide lines for the application and implementation of programming languages for programmable controls


    The IEC 61131-3 norm is an international standard for programming languages of programmable logic controllers (PLC).

    The norm contains five programming languages:

    • instruction l (AWL or IL)
    • function chart (FUP or FBD)
    • ladder diagram (KOP or LD)
    • sequential function chart (AS or SFC)
    • structured text (ST)

    The programming languages realised in CODESYS conform to the norm demands. A program consists of following elements after that standard:

    • structures
    • components
    • global variables

    The general language elements are described in the following sector:

    • identifier
    • address
    • types
    • commends
    • constants