pair fails, the other will take full ownership of the disk drives and tasks it was undertaking, providing continuous availability to that data and continuous operation of the system, including re-driving disk I/Os. A running primary process may be given a backup process in another CPU, which receives checkpoint information. If the primary process fails, the backup process resumes the transaction using the checkpoint information. The backup process may also spawn its own backup to avoid data loss in case there are further failures. The name "NonStop" refers to this fault-tolerant design. HPE NonStop systems can support operations involving high transactions-per-second and are therefore used in critical applications such as banking, stock trading platforms and telecommunications systems. Upon the NonStop OS platform there are at least two programming languages—TAL (Transaction Application Language) as the compiled language, and TACL as the interpreted language. NonStop OS software includes compilers for other languages (including Java, C, C++, COBOL, SCOBOL, etc.), which may be used to support functions in languages other than TAL/TACL if required. TACL remains as the default scripting language on these machines. HPE later introduced a ksh-based shell command interface, however this does not contain every capability offered by TACL such as the netstat command. TACL built-ins reflect the multi-CPU nature of NSK. TACL instructions can be stored in a simple text file as MACROS, ROUTINES, or DEFINES which the TACL interpreter can execute as scripts. Such scripts are often used to store complex configuration instructions such as start-up and hardware configuration sequences. TACL is also used as a job control language for batch jobs. The TACL language has a large number of built-in utilities which allow the user to capture and parse output from various system utilities. This allows users to build TACL programs that can monitor system events through the use of filters that monitor the system and application event logs. Example uses of TACL A TACL routine saved in the file FILE1 Create the following subroutine in the file FILE1: ?Section HELLO_BERNARD ROUTINE #OUTPUT Hello BERNARD How to run the TACL routine: From a TACL prompt type: LOAD / KEEP 1 / FILE1 (this loads the routine into memory) Type: HELLO_BERNARD (this runs the routine) Output will be: Hello BERNARD TACL code in the file FILE1 An alternate strategy is to create a file named FILE1 and add the following two lines: ?TACL ROUTINE #OUTPUT Hello BERNARD Execute