LEGO MINDSTORMS Robots Manual page 69

int count;
task main() {
CreateDatalog(20);
ClearTimer(0);
SetSensor(SENSOR_1, SENSOR_TOUCH);
count = 0;
until (count == 20) {
until(SENSOR_1 == 1);
AddToDatalog(Timer(0));
count++;
until(SENSOR_1 == 0);
}
}
When you run this program, you'll notice the RCX shows the status of the datalog on the right side of the display. It looks kind of like a pie; as you add values to the datalog the pie fills up.
To upload a datalog to the PC, you can use nqc's -datalog option, which simply dumps the values to the screen:
C:\>nqc -datalog
8
12
16
19
23
25
27
29
31
33
39
47
52
56
59
62
65
68
71
75
C:\>
The datalog actually stores the source of every value. If you use a tool like RCX Command Center, it can show you the source of each value in the datalog. In Chapter 8, Using Spirit.ocx with
Visual Basic, I'll show you how to write your own program in Visual Basic to retrieve the contents of the datalog.
Tasks
NQC gives you powerful control over tasks and subroutines. Each of the RCX's five programs is made up of one or more tasks. These tasks can execute at the same time, which is another way of
saying that the RCX is multitasking.
Tasks are defined using the task command. Every program must have a main task which is executed when the program is first started. Other tasks must be started and stopped explicitly:
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