e current process state, the signal will be discarded (lost). This is called an implicit transition. In Figure 2.15, left part, the FIFO queue of process display contains the signals blue, green and red. Process display being in state idle, the signal blue is discarded (lost), and then green is input, leading to state resizing. Signal red is now first in the queue. block b2 process display block b2 green green display resizing display blue, blue, green state: idle green state: resizing Figure 2.15 The FIFO queue of one instance of process display 2.3.5 Save To avoid losing signal blue as in Figure 2.15, we add a save symbol below state idle, as depicted in Figure 2.16. When a signal is saved, it stays in the input queue at the same position, and the next signals in the queue are examined to see if they can be input, saved or discarded. process display This is a resizing green resizing step 1 step 2 step 3 green queue head current state resizing action inputgreen input blue Figure 2.16 Saving signal blue Quick Tutorial on SDL 17 Reading the table in Figure 2.16 helps you understand how the save works: 1. From state idle, blue is first in the queue: it remains here because it is saved, and the next signal in the queue, green, can be input, leading to state resizing. 2. From state resizing, blue is input, and we go to state s3. 2.3.6 Variables Variables are used to store data in process instances. Variables cannot be declared in systems or blocks: global variables do not exist in SDL. Figure 2.17 shows an example of variable declaration and usage: the variable n of type Integer is declared, set to 0 upon process instance start, and then incremented by 1 each time a disc signal is input. We remind you that if, for example, two instances of process DLC are created, each instance has its own variable n in its context. process DLC n Integer; n:= n+1 Figure 2.17 Example of variable 2.3.7 Stop After executing a stop symbol, the process instance and its associated input queue and the signals it contains are immediately des