1. CGS 3460 Program looping n Why we need loop lMake code concise for repetitive processes n When to use loop lRun a block of code repetitively lProcess multiple data using same procedure n How to use loop lfor lwhile ldo

2. CGS 3460 for loop n Format: for( init_expression; loop_condition; loop_expression ) { program statement; } n Flow: Condition satisfied? No Initial Expression Yes Program statement loop expression

3. CGS 3460 while loop n Format while (loop_condition) { program statement; } n Flow Condition satisfied? Program statement Yes No

4. CGS 3460 for loop vs while loop Condition satisfied? No Initial Expression Yes Program statement loop expression Condition satisfied? Program statement Yes No for loopwhile loop

5. CGS 3460 Convert for loop to while loop while (loop_condition) { program statement; } for( init_expression; loop_condition; loop_expression ) { program statement; } program statement; loop_expression; init_expression; while(loop_condition) { }

6. CGS 3460 Convert for to while – Example F = 1; N = 10; for(M=1; M<=N; M=M +1) { F = F * M; } init_expression; while(loop_condition) { program statement; loop_expression; } F = 1; N = 10; M = 1; while(M<=N) { } F = F * M; M = M +1;

7. CGS 3460 do-while loop n Format do { program statement } while (loop_condition); Condition satisfied? Program statement Yes No

8. CGS 3460 while and do-while loop n In while loop, program statement may never be evaluated. While in do-while loop, it is evaluated at least once Condition satisfied? Program statement Yes No while (loop_condition) { program statement; } do { program statement } while (loop_condition); Condition satisfied? Program statement Yes No

9. CGS 3460 Example p = 7; c = 1; p = 1; do { p = p + c; c++; } while( c<= 3 ); Code 2 c = 1; p = 1; while( c <= 3 ) { p = p + c; c++; } Code 1

10. CGS 3460 Example p = 1;p = 6; c = 5; p = 1; do { p = p + c; c++; } while( c<= 3 ); Code 2 c = 5; p = 1; while( c<= 3 ) { p = p + c; c++; } Code 1

11. CGS 3460 break n Used to break out of a loop immediately lPossibly due to detection of an error int i; for(i=0; i < 3; i++) { printf(“here\n”); break; printf(“there\n”); } here

12. CGS 3460 continue n Used to continue at the next point lPossibly due to detection of an error int i = 0; for(i=0; i < 3; i++) { printf(“here\n”); continue; printf(“there\n”); } here

13. CGS 3460 Example – summation of valid scores count = 0; n = 10; sum = 0; while (count < n) { scanf("%d", &score); if (score 100) continue; count++; sum = sum + score; }

14. CGS 3460 Example – summation of valid scores count = 0; n = 10; sum = 0; while (count < n) { scanf("%d", &score); if (score 100) { printf(“Wrong data. Exiting program\n”); break; } count++; sum = sum + score; }