Sams Teach Yourself C++ in 21 Days

: 1

Task One!

**** Menu ****

(1) Choice one.

(2) Choice two.

(3) Choice three.

(4) Redisplay menu.

(5) Quit.

: 3

Task Three!

**** Menu ****

(1) Choice one.

(2) Choice two.

(3) Choice three.

(4) Redisplay menu.

(5) Quit.

: 5

This program brings together a number of concepts from today and previous

days. It also shows a common use of the switchstatement.

The forever loop begins on line 15. The menu()function is called, which prints the menu

to the screen and returns the user’s selection. The switchstatement, which begins on line

18 and ends on line 38, switches on the user’s choice.

If the user enters 1, execution jumps to the case (1):statement on line 20. Line 21

switches execution to the DoTaskOne()function, which prints a message and returns. On

its return, execution resumes on line 22, where the breakends the switchstatement, and

execution falls through to line 39. On line 40, the variable exitis evaluated to see

whether it is true. If it evaluates true, the breakon line 41 is executed and the for(;;)

loop ends; but if it evaluates false, execution resumes at the top of the loop on line 15.

Note that the continuestatement on line 30 is redundant. If it were left out and the

breakstatement were encountered, the switch would end,exitwould evaluate false, the

loop would reiterate, and the menu would be reprinted. The continuedoes, however,

bypass the test of exit.

204 Day 7

ANALYSIS

DOcarefully document all intentional

fall-through cases.

DOput a default case in switchstate-

ments, if only to detect seemingly impos-

sible situations.

DON’Tuse complex if...elsestate-

ments if a clearer switchstatement will

work.

DON’Tforget breakat the end of each

case unless you want to fall through.

DO DON’T