Chapter 05

Problem Solving and Program Design in C (5th Edition) by Jeri R. Hanly and Elliot B. Koffman

CP 202 Chapter 5

CHAPTER 5

Compound Assignment Operators 

When an assignment statement in the form: variable = variable op expression;

For example, x = x + 1;

an alternative way of writing the statement is: variable op= expression;

For example, x += 1; 

Increment (++) / Decrement (--) x = x++;

≡

x += 1;

≡

x = x + 1;

While Statement Introduction   



Loop repetition condition. The statement (loop body) is executed while the condition is True. Avoid infinity loop.

condition F

Syntax while (loop repetition condition) statement or while (loop repetition condition) { statements // loop body }

A

T loop body



B C

Flow Diagram for (while)

While Statement Example 1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33

int command, money, balance = 0; printf("Enter command number:\n“); printf(" 0 - quit\n"); printf(" 1 - deposit money\n"); printf(" 2 - withdraw money\n"); printf(" 3 - print balance\n"); scanf("%d", &command); while (command != 0) // stop the loop if command = 0 { switch (command) { case 1: // deposit code printf("Enter deposit amount: "); scanf("%d", &money); balance = balance + money; break; case 2: // withdraw code printf("Enter withdraw amount: "); scanf("%d", &money); balance = balance - money; break; case 3: // print code printf("Current balance = %d\n", balance); break; default: printf("Error\n"); } printf(“Enter command number: “); scanf("%d", &command); } printf("See you later!\n");

While Statement Example 1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33

int command, money, balance = 0; printf("Enter command number:\n“); printf(" 0 - quit\n"); printf(" 1 - deposit money\n"); printf(" 2 - withdraw money\n"); printf(" 3 - print balance\n"); scanf("%d", &command);

0. loop control variable 1. initialization

while (command != 0) // stop the loop if command = 0 { switch (command) { case 1: // deposit code printf("Enter deposit amount: "); scanf("%d", &money); balance = balance + money; break; case 2: // withdraw code printf("Enter withdraw amount: "); scanf("%d", &money); balance = balance - money; break; case 3: // print code printf("Current balance = %d\n", balance); break; default: printf("Error\n"); } printf(“Enter command number: “); scanf("%d", &command); } printf("See you later!\n");

2. loop repetition condition

3. Updating

Draw the flow diagram for this program?

While Statement Example 2 

Check the book:    

Compute company payroll (example 5.1 in the book) See the program at Figure 5.4 See the output at Figure 5.4 Trace the memory. See Table 5.2

While Statement Example 2

While Statement Example 2

0. loop control variable 1. initialization 2. loop repetition condition

3. Updating

Draw the flow diagram for this program?

While Statement Example 2 (OUTPUT) statement count_emp < number_emp scanf(“%lf”,&hours); scanf(“%lf”,&rate);

hours

rate

pay

total_pay

count_emp

?

?

?

0.0

0 True get hours get rate

50.0 5.25

Pay = hours * rate;

262.5

total_pay = total_pay + pay;

find pay 262.5

count_emp = count_emp +1; count_emp < number_emp scanf(“%lf”,&hours); scanf(“%lf”,&rate); Pay = hours * rate;

count_emp = count_emp +1;

increment count_emp True get hours get rate find pay

6.0 5.0 30.0 292.5

count_emp = count_emp +1;

total_pay = total_pay + pay;

add to total_pay 1

total_pay = total_pay + pay;

count_emp < number_emp scanf(“%lf”,&hours); scanf(“%lf”,&rate); Pay = hours * rate;

Effect

add to total_pay 2

increment count_emp True get hours get rate find pay

15.0 7.0 105.0 397.5

add to total_pay 3

increment count_emp

Do-While Statement Introduction  



Loop repetition condition. The statement (loop body) is executed once before checking the condition.

loop body



A B

Syntax do

condition

statement while (loop repetition condition);

F

or

C

do { statements // loop body } while (loop repetition condition);

Flow Diagram for (do-while)

T

Do-While Statement Example 1 

char letter;



do {



printf("Enter a letter from A through E to exit the loop: ");



scanf(“%c", &letter);



} while (letter < ‘A’ || letter > ‘E’);

Draw the flow diagram for this program?

Do-While Statement Example 2 

Check the book:  

Validating input using do-while statement (example 5.10) See the program at Figure 5.14

#include<stdio.h> int get_int(int n_min,int n_max) { int in_val, /* input - number entered by user status; /* status value returned by scanf char skip_ch; /* character to skip int error; /* error flag for bad input */

Do-While Statement Example 2

*/ */ */

/* Get data from user until in_val is in the range. */ do { error=0; // No errors detected yet. /* Get a number from the user. */ printf("Enter an integer in the range from %d ",n_min); printf("to %d inclusive> ",n_max); status=scanf("%d",&in_val); printf("status = %d ",status); /* Validate the number */ if(status!=1) /* in_val didn't get a number { error=1; scanf("%c",&skip_ch); printf("\nskip_ch = %c\n",skip_ch); printf("invalid character >>%c>>. ",skip_ch); printf("Skipping rest of line. \n"); } else if(in_valn_max) { error=1; printf("Number %d is not in range.\n",in_val); } /* Skip rest of data line. do scanf("%c",&skip_ch); while(skip_ch!='\n');

*/

*/

} while(error); return(in_val); } int main(void) { int i=get_int(10,20); printf("i=%d\n",i); return(0); }

Draw the flow diagram for this program?

For Statement Introduction 



Three components:  Initialization of the loop control variable.  Test of the loop repetition condition.  Change (update) of the loop control variable.

Syntax for (initialization expression; loop repetition condition; update expression) { statements // loop body }

initial update condition

T

F

A

loop body



B C

Flow Diagram for (for)

For Statement Example 1   

/* display N asterisks */ for (count_star = 0; count_star < N; count_star += 1) printf(“*");

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For Statement Example 2

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Nested Loop 

Loops inside Loops

Nested Loop Example 1

Nested Loop Example 1

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Nested Loop Example 2

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Case Study: Collecting Area for Solar-Heated House 

Review Section 5.9 from the book.

Learn in the Lab 

How to Debug and Test Programs? 

Review Section 5.10 from the book.