1. Program Control Topics While loop For loop Switch statement
The Do/While loop
The break and continue Statements
Logical Operators

2. While Loop
Example:
int counter =1; //initialization
while (counter <= 10){ //repetition condition
printf( "%d\n", counter );
++counter; //increment }
int counter = 1; names counter, declares it to be an integer, reserves space for it in memory, and sets it to an initial value of 1
pitt

3. while Loop while (condition) statement_to_repeat; while (condition) {
...
statement_N; }
/* Weight loss program */
while ( weight > 500 )
weight--;
while ( weight > 500 ) {
printf("Go, exercise, ");
printf("then come back. \n");
printf("Enter your weight: ");
scanf("%d", &weight);}
University of Pittsburgh-CSD-Khalifa

4. Loops & break Statement
Break out of the loop { }
can use with
while
do while
for
switch
does not work with
if {}
else {}
University of Pittsburgh-CSD-Khalifa

5. break Statement fact = 1; /* initialize factorial */ i = 1;
while( i<10 ){ /* run loop –break when fact >100*/
fact = fact * i;
if ( fact > 100 ){
printf ("Factorial of %d above 100", i);
break; /* break out of the while loop */ }
i ++ ;
} /* end while loop */
University of Pittsburgh-CSD-Khalifa

6. continue Statement Jumps to the beginning of the loop
fact = 1; i = 1; /* a program to calculate 10 !
while ( 1 ){
fact = fact * i;
i ++ ;
if( i<10 )
continue; /* not done yet ! Go to loop and perform next iteration*/
break; }
University of Pittsburgh-CSD-Khalifa

7. The do/while repetition structure
The do/while Loop
The do/while repetition structure
Similar to the while structure
Condition for repetition tested after the body of the loop is performed
All actions are performed at least once
Format: do { statement } while ( condition );
Good practice to put brackets in, even if not required

8. Example (letting counter = 1)
The do/while Loop
Example (letting counter = 1)
do {
printf( "%d ", counter );
} while (++counter <= 10);
Prints the integers from 1 to 10

9. The do/while Loop
true
false
action(s)
condition

10. 1. Initialize variable 2. Loop 3. Print Program Output
1 /*
2 Using the do/while repetition structure */
3 #include <stdio.h> 4
5 int main()
6 {
7 int counter = 1; 8
9 do {
printf( "%d ", counter );
11 } while ( ++counter <= 10 ); 12
13 return 0;
14 }
1. Initialize variable
2. Loop
3. Print
Program Output

11. The break and continue Statements
Causes immediate exit from a while, for, do/while or switch structure
Program execution continues with the first statement after the structure
Common uses of the break statement
Escape early from a loop
Skip the remainder of a switch structure

12. The break and continue Statements (II)
Skips the remaining statements in the body of a while, for or do/while structure
Proceeds with the next iteration of the loop
while and do/while
Loop-continuation test is evaluated immediately after the continue statement is executed
for structure
Increment expression is executed, then the loop-continuation test is evaluated

13. 1. Initialize variable 2. Loop 3. Print Program Output
1 /*
2 Using the continue statement in a for structure */
3 #include <stdio.h> 4
5 int main()
6 {
7 int x; 8
9 for ( x = 1; x <= 10; x++ ) { 10
if ( x == 5 )
continue; /* skip remaining code in loop only
if x == 5 */ 14
printf( "%d ", x );
16 } 17
18 printf( "\nUsed continue to skip printing the value 5\n" );
19 return 0;
20 }
1. Initialize variable
2. Loop
3. Print
Program Output
Used continue to skip printing the value 5

14. for Statement for (initial; condition; iteration)
statement_to_repeat;
for (initial; condition; iteration) {
statement_1;
...
statement_N; }
fact = 1; /* Calculate 10 ! */
for ( i = 1; i < =10; i++)
fact = fact * i;
fact = 1;
for (int i = 1; i < 10; i++) {
fact = fact * i;
printf(“value of fact= %d \n”, fact);
if ( fact > 100 )
break; }
University of Pittsburgh-CSD-Khalifa

15. Format when using for loops
The for Loop
Format when using for loops
for ( initialization; loopContinuationTest; increment ) statement
Example:
for( int counter = 1; counter <= 10; counter++ )
printf( "%d\n", counter );
Prints the integers from one to ten.
No semicolon after last expression

16. For loops can usually be rewritten as while loops: initialization;
The for Loop
For loops can usually be rewritten as while loops:
initialization;
while ( loopContinuationTest){ statement increment; }
Initialization and increment
Can be comma-separated lists
for (int i = 0, j = 0; j + i <= 10; j++, i++ )
printf( "%d\n", j + i );

17. Examples Using the for Structure
1 /*
2 Summation with for */
3 #include <stdio.h> 4
5 int main()
6 {
7 int sum = 0, number; 8
9 for ( number = 2; number <= 100; number += 2 )
sum += number; 11
12 printf( "Sum is %d\n", sum ); 13
14 return 0;
15 }
Examples Using the for Structure
Program to sum the even numbers from 2 to 100
Program Output
Sum is 2550

18. switch Statement switch ( letter ) { switch( expression ) { case 'A':
printf("First letter\n");
break;
case 'Z':
printf("Last letter\n");
default :
printf("Middle letter\n"); }
University of Pittsburgh-CSD-Khalifa
switch( expression ) {
case constant1 :
statement;
...
break;
case constantN :
default :
break;}

19. switch Format The switch Statement
Useful when a variable or expression is tested for all the values it can assume and different actions are taken.
Format
Series of case labels and an optional default case
switch ( value ){
case '1':
actions
case '2':
default: }
break; causes exit from structure

20. The switch Multiple-Selection Structure (II)
true
false .
case a
case a action(s)
break
case b
case b action(s)
case z
case z action(s)
default action(s)

21. 2.1 Use switch loop to update count
1 /*
2 Counting letter grades */
3 #include <stdio.h> 4
5 int main()
6 {
7 int grade;
8 int aCount = 0, bCount = 0, cCount = 0,
dCount = 0, fCount = 0; 10
11 printf( "Enter the letter grades.\n" );
12 printf( "Enter the EOF character to end input.\n" ); 13
14 while ( ( grade = getchar() ) != EOF ) { 15
switch ( grade ) { /* switch nested in while */ 17
case 'A': case 'a': /* grade was uppercase A */
aCount; /* or lowercase a */
break; 21
case 'B': case 'b': /* grade was uppercase B */
bCount; /* or lowercase b */
break; 25
case 'C': case 'c': /* grade was uppercase C */
cCount; /* or lowercase c */
break; 29
case 'D': case 'd': /* grade was uppercase D */
dCount; /* or lowercase d */
break;
1. Initialize variables
2. Input data
2.1 Use switch loop to update count

22. 2.1 Use switch loop to update count 3. Print results33
case 'F': case 'f': /* grade was uppercase F */
fCount; /* or lowercase f */
break; 37
case '\n': case' ': /* ignore these in input */
break; 40
default: /* catch all other characters */
printf( "Incorrect letter grade entered." );
printf( " Enter a new grade.\n" );
break; }
46 } 47
48 printf( "\nTotals for each letter grade are:\n" );
49 printf( "A: %d\n", aCount );
50 printf( "B: %d\n", bCount );
51 printf( "C: %d\n", cCount );
52 printf( "D: %d\n", dCount );
53 printf( "F: %d\n", fCount ); 54
55 return 0;
56 }
2.1 Use switch loop to update count
3. Print results

23. Program Output Enter the letter grades.
Enter the EOF character to end input. A B C D F E
Incorrect letter grade entered. Enter a new grade.
/* in UNIX: use <return> <ctrl-d> for EOF */
Totals for each letter grade are:
A: 3
B: 2
C: 3
D: 2
F: 1
Program Output

24. Variable Scope Printout: -------------- A = 3 A = 2 A = 1 int A;
void main() {
A = 1;
myProc();
printf ( "A = %d\n", A); }
void myProc()
int A = 2;
while( A==2 )
int A = 3;
break;
. . .
Variable Scope
Printout:
A = 3
A = 2
A = 1
University of Pittsburgh-CSD-Khalifa

25. Logical Operators && (logical AND) || (logical OR)
Returns true if both conditions are true
|| (logical OR)
Returns true if either of its conditions are true
! (logical NOT, logical negation)
Reverses the truth/falsity of its condition
Unary operator, has one operand
Useful as conditions in loops
Expression Result
true && false false true || false true
!false true