4.14 Flow Control

Remove the element S0 and load IP with A, if S0 is false.

Remove the element S0 and load IP with A, if S0 is true.

Push the current value of IP and then load IP with A.

Push the current value of IP and then load IP with S0. The destination of CALR is implicitly located in the code array of the program. Branches to the data array cannot be done.

Remove two elements S0 and S1 and load IP with A, if S1 <= S0. (*)

Call the interface procedure located at slot N. Slot values are dynamically generated using IPROC, IREF, and ICALX. The interface procedure may return a machine word size return value in RR. The stack must me cleaned up using CLEAN after calling an interface procedure. Interface procedures are normally implemented in languages other than T3X (such as C or assembly language). They are used to extend the T3X runtime environment. The exact semantics of ICALL depend on the called procedure.

Halt the Tcode machine. The least significant eight bits of N will be delivered to the invoking process as a return code.

Load IP with A.

Load IP with A, if S0 is false. Do not remove S0.

Load IP with A, if S0 is true. Do not remove S0.

Remove two elements S0 and S1 and load IP with A, if S1 >= S0. (*)

(*) The UNEXT and DNEXT instructions have been designed for use in counting loops (FOR-NEXT loops in BASIC). The idea is as follows: At the end of the loop, the current loop index and the loop limit are both pushed onto the stack. UNEXT compares the values and branches out of the loop, if index>=limit. DNEXT branches, if index<=limit. Therefore, UNEXT is used in upward counting loops and DNEXT is used in countdown loops.