Section 10: The Index Register and Loop Control 109

To Labels. If the RI value is positive, t V and G V will transfer execution to the label which corresponds to the number in the Index register (see the above table).

For instance, if the Index register contains 20.00500, then a tV instruction will transfer program execution to ´b A. See the chart on page 107.

To Line numbers. If the RI value is negative, tV causes branching to that line number (using the absolute value of the integer portion of the value in RI).

For instance, if RI contains –20.00500, then a tV instruction will transfer program execution to program line 020.

Indirect Flag Control With V

F V, " V, or ? V will set, clear, or test the flag (0 to 9) specified in RI (by the magnitude of the integer portion).

Indirect Display Format Control With V

´• V, ´ i V, and ´ ^ V will format the

display in their customary manner (refer to pages 58–59), using the number in RI (integer part only) for n, which must be from 0 to 9.*

Loop Control With Counters: Iand e

The I (increment and skip if greater than) and e (decrement and skip if less than or equal to) functions control loop execution by referencing and altering a loop control number in a given register. Program execution (skipping a line or not) then depends on that number.

The key sequence is ´{ I, e} register number. This number is 0 to 9, .0 to .9, V,or %.

The Loop Control Number. The format of the loop control number is:

 

±nnnnn

is the current counter value,

nnnnn.xxxyy, where

xxx

is the test (goal) value, and

 

yy

Is the increment of decrement value

*Except when using f(section 14)