usedmeter = currentmeter - previousmeter kwhcharge = KWH1 CHARGE * usedmeter

Transcription

1 Electric Bill Program: Analysis inputs: previousmeter, currentmeter, andpriorbalance outputs: latecharge, kwhcharge, andtotalcharge constants: BASIC CHARGE (10.50), LATE CHARGE (5.00), TIER BOUNDARY (250), KWH1 CHARGE (.15), and KWH2 CHARGE (.17) formulas: usedmeter = currentmeter - previousmeter kwhcharge = KWH1 CHARGE * usedmeter kwhcharge = KWH1 CHARGE * TIER BOUNDARY + KWH 2CHARGE * (usedmeter - TIER BOUNDARY) totalcharge = priorbalance + BASIC CHARGE + latecharge + kwhcharge 35

2 Electric Bill Program: Algorithm obtain inputs perform calculations determine if late charge is applicable select formula to calculate kwhcharge produce outputs 36

3 ElectricBill.c: Beginning /* ElectricBill.c * ============== * This program determines a customer s electric bill. * * It demonstrates both the simple if and the if/else statement. */ #include <stdio.h> /* current pricing information */ #define BASIC_CHARGE #define TIER_BOUNDARY 250 #define KWH1_CHARGE.15 #define KWH2_CHARGE.17 #define LATE_CHARGE

4 ElectricBill.c: Obtain Inputs int main() { int previousmeter, currentmeter; /* inputs */ double priorbalance; /* input */ int usedmeter; /* intermediate */ double latecharge = 0.00, kwhcharge, totalcharge; /* outputs */ /* obtain inputs */ printf("please enter the following information.\n\n"); printf("previous meter reading: "); scanf("%d", &previousmeter); printf("current meter reading: "); scanf("%d", &currentmeter); printf("prior balance: "); scanf("%lf", &priorbalance); 38

5 ElectricBill.c: Perform Calculations /* perform calculations */ if (priorbalance > 0.00) latecharge = LATE_CHARGE; usedmeter = currentmeter - previousmeter; if (usedmeter <= TIER_BOUNDARY) kwhcharge = KWH1_CHARGE * usedmeter; else kwhcharge = KWH1_CHARGE * TIER_BOUNDARY + KWH2_CHARGE * (usedmeter - TIER_BOUNDARY); totalcharge = priorbalance + BASIC_CHARGE + latecharge + kwhcharge; 39

6 ElectricBill.c: Produce Outputs /* produce outputs */ printf("\nyour BILL\n\n" "Prior Balance: %5.2f\n" "Basic Charge: %5.2f\n" "Late Charge: %5.2f\n" "KWH Charge: %5.2f\n\n" "TOTAL CHARGE: %5.2f\n", priorbalance, BASIC_CHARGE, latecharge, kwhcharge, totalcharge); } return 0; 40

7 Counter Controlled Repetition Controlled Repetition 41

8 Control Structures programs use control structures to specify the order in which statements are executed C programs use four major control structures: sequential (statements are executed from top to bottom) conditional or selection (statements may be skipped ) repetitive or iterative (statements executed many times) function call and return 42

9 syntax: The C for Loop Statement execution: for (expression1; expression2; expression3) statement ➊ evaluate expression1 (the initialization expression) ➋ evaluate expression2 (the test expression) if it is 0, thefor statement has been completed ➌ execute statement (the for loop body) ➍ evaluate expression3 (the increment expression); go back to step ➋ 43

10 Counter Controlled Repetition counter controlled repetition involves repeatedly executing a statement a specific number of times counter controlled repetition is also called definite repetition or definite iteration the repeat N times construct counter controlled repetition is best achieved in C by using the for statement: initialization expression assigns 0 to a counter test expression compares the counter to the desired number of repetitions increment expression adds 1 to the counter 44

11 Examples of the for Statement to print a number of asterisks equal to the value of a variable called stars for (i = 0; i < stars; i = i + 1) printf("*"); to print a series of numbered lines equal to the value of variable lines, starting at 0 for (i = 0; i < lines; ++i) printf("\n%d", i); 45

12 Textbook Reading the for loop statement is covered in sections 4.1 to4.6 counter controlled repetition is introduced in sections 3.7 and3.8 shortcut assignment operators are covered in sections 3.11 and