Using Mapping Services › NCL Reference, Type Checking, and Data Behavior › BIT STRING Type › Boolean BIT STRING Access

Boolean BIT STRING Access

Boolean BIT STRING access deals with individual bit level access and operates only through named values. This access is recommended because program access to bits is only via their symbolic named values, thus removing from NCL the need to know relative bit positions.

For Boolean BIT STRING access to be invoked, the named value of a bit is provided by NCL as an additional name segment after the BIT STRING component name. Since the BIT STRING type is primitive, the additional name in the name hierarchy is understood to be a named value, and is treated as a BOOLEAN type. No matter where the named value is in the BIT STRING the value of the bit is always 0 or 1, as for a BOOLEAN type.

External Form - Input

The local character strings TRUE and FALSE (not case sensitive) are accepted, while the digit 0 is interpreted as false, and the digit 1 is true. Null is a type check in this case.

External Form - Output

The digit 0 (false) or 1 (true) is always returned.

Local Form and Behavior

The component name plus the named value is treated as a reference to a specific bit (the bit position within the component being defined by the named value), and that bit is set to 0 or 1 depending upon the input. No other bits in the BIT STRING component are affected. If the component is extended to accommodate the input then all other bits are set to 0.