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16.216 ECE Application Programming

16.216 ECE Application Programming. Instructor: Dr. Michael Geiger Fall 2011 Lecture 24: Finishing PE4: Functions. Lecture outline. Announcements/reminders Removing project; programs now worth 60% Exam 2: Wednesday 11/9 Allowed 1 double-sided sheet of notes

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16.216 ECE Application Programming

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  1. 16.216ECE Application Programming Instructor: Dr. Michael Geiger Fall 2011 Lecture 24: Finishing PE4: Functions

  2. Lecture outline • Announcements/reminders • Removing project; programsnow worth 60% • Exam 2: Wednesday 11/9 • Allowed 1 double-sided sheet of notes • Practice problems to be posted over weekend • Prog. 6 to be posted this weekend; due Mon, 11/14 • Prog. 5 grading done today; regrades due Mon, 11/7 • No late penalties; will post solution 11/7 • Today: Finishing PE4 (functions) • Identify where function(s) can be used • Write code • Test using debugger ECE Application Programming: Lecture 24

  3. PE4: Change problem • Given any amount of change under $2.00, determine and print out the minimum number of coins required to make that amount of change. • Available coins are Halves (half dollars), Quarters, Dimes, Nickels, and Pennies. ECE Application Programming: Lecture 24

  4. Flowcharting - Sample Start nHalves = 0 Given some amount of money, amount, how many half dollars would be returned? myAmt = amount myAmt < 0.50 myAmt = myAmt - 0.50 scanf amount printf nHalves nHalves = nHalves + 1 Finish ECE Application Programming: Lecture 24

  5. Expand to all coins - page 1 A Start nH = 0 scanf amount myAmt < 0.50 myAmt = amount A myAmt = myAmt - 0.50 nH = nH+ 1 B ECE Application Programming: Lecture 24

  6. B C nQ = 0 nN = 0 myAmt < 0.25 myAmt < 0.05 myAmt = myAmt - 0.25 myAmt = myAmt - 0.05 nQ = nQ + 1 nN = nN + 1 nD = 0 nP = 0 myAmt < 0.10 myAmt < 0.01 myAmt = myAmt - 0.10 myAmt = myAmt - 0.01 nD = nD + 1 nP = nP + 1 ECE Application Programming: Lecture 24 C D

  7. D printf nH,nQ,nD,nN,nP Finish ECE Application Programming: Lecture 24

  8. When to use functions • Find a particular step or series of steps being repeated in your code • If code is exactly the same, you need no arguments • If one or more values change, but the actual calculations that need them are the same, those values can be parameters of your function (arguments) • Reassess change example • Steps for creating change are extremely similar • What changes each time? • How should we use those values in a function? • Inputs, outputs, variables … ? ECE Application Programming: Lecture 24

  9. B General case: nC=number coins Output vC=value of coin Input myAmt=amt left Input/Output nQ = 0; vQ=0.25 myAmt < vQ myAmt = myAmt - vQ nQ = nQ + 1 function: change nC = 0; vC=input nD = 0; vD=0.10 myAmt < vC myAmt < vD myAmt = myAmt - vC myAmt = myAmt - vD nC = nC + 1 nD = nD + 1 return ECE Application Programming: Lecture 24 C

  10. Start General case: nC=number coins Output vC=value of coin Input myAmt=amt left Input/Output scanf amount myAmt = amount change(&nH,0.5,&myAmt) function:change (addr nC, val vC, addr Amt) change(&nQ,0.25,&myAmt) change(&nD,0.1,&myAmt) *nC = 0; vC=input *myAmt < vC change(&nN,0.05,&myAmt) change(&nP,0.01,&myAmt) *myAmt = *myAmt - vC printf nH,nQ,nD,nN,nP *nC = *nC + 1 return ECE Application Programming: Lecture 24 Finish

  11. Next time • Exam 1 Preview ECE Application Programming: Lecture 24

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