Lessons

Credits for Lecturing and Authoring
Nested Loops
Nested For Loops
Flag Controlled Loops
Sample Program

Nesting is a programming concept where one control structure is placed inside another.

Nested loops can be extremely useful, but also confusing to deal with.

Remember, for each iteration of the outer loop, the inner loop is executed and repeated until done.

Two for loops must use different control variables!

Example:

				Results
for (m=1; m<=4; m++) { (m) (n) for (n="1;" n<="3;" n++) { 1 1 printf("%d %d\n", m, n); 1 2 } 1 3 } 2 1 2 2 2 3 3 1 Note: Inside loop is 3 2 executed 3 times for 3 3 each of the 4 times the 4 1 outside loop is executed! 4 2 4 3 

Loop structures can become complicated and hard to follow. It can sometimes be difficult and confusing to place an expression in its ususal spot.

Many times a flag can help to simplify the condition.

A flag is type int variable used to represent whether or not a certain event has occured. It is often initialized to 0 where it remains until the event occurs. When the event occurs, the flag is changed to 1.

The following program uses a while loop to approximate a root of the function 2x²-6.2x+3.6 using the interval-halving method. The variable done is a flag used to determine when the root has been approximated to the desired precision (TOL). When the desired precision is reached, the flag, done changes and looping can stop.