lecture12-feb15

lecture12-feb15 - Announcements Lecture 12 Assignment 3 out...

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1 Announcements Lecture 12 • Assignment 3 out today – Designs due on Friday at the beginning of your recitation session • Functional block diagram, algorithm, IPO diagram IPO diagram describes the inputs, outputs and general operations to be performed Functional block diagram shows who calls who (functions), and data passed back and forth (without library functions) Algorithm is a procedure (i.e. a sequence of steps/instructions) for solving a given problem. Flowchart or pseudocode OK. » Tip : level of abstraction should be at least 1:10 • Exam 1 - Friday in class – Study tip: work the sample exam, specific exercises in the book (on Wed.), solutions for most are on BB • Topics for today – More on functions (passing arrays back and forth) – Modular sorting program example – Recursive functions Functions – reminder #include <stdio.h> float max(float, float); /* fcn prototype */ int main(void) { int x, y; printf("Enter two numbers: "); scanf("%d%d", &x, &y); printf("The larger number is %g\n", max(x, y) ); /* call*/ return 0; } float max(float a, float b) /* definition of function */ { if (a > b) return a; else return b; } main max 2 #s (x,y) the larger of the 2 #s Order of events 1. max() is called with x and y as arguments 2. x, y are [converted] & copied into a & b 3. The body of max is executed 4. The return statement returns the value of either a or b back to the call 5. The value returned is used to output /* average is a function that computes and returns the average of the values in a given (passed) integer array of given length */ double average ( int data [ ] , int length) { if (length = = 0) return 0; double sum = 0; int i; for (i = 0; i < length; i++) sum = sum + data[i]; return sum / length; } Passing an Array as an Argument data exam1scores Array names are passed as a pointer Called from your main function, e.g. double avg; int exam1scores [CLASS_SIZE]; /* assume the full array gets its values somehow */ avg = average ( exam1scores , CLASS_SIZE); • /* This function fills in an integer array with random scores, each in the range from 0 to n */ void randomData ( int data [ ] , int length, int n) {int i; for (i = 0; i < length; i++) data[i] = rand ( ) % (n + 1); return; } • Called in the main for example as randomData ( exam1scores , CLASS_SIZE, 100); Returning a Filled-in Array rand( ) returns a random positive int; see pg 686[old 570] Passing Multi-dimensional Arrays • Only the length of the first dimension can be omitted /* sum up the values in a n x 10 matrix of ints */ #define LEN 10 . . . int sum_array(int a[ ] [LEN], int n)

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This note was uploaded on 03/15/2010 for the course EE 16005 taught by Professor Krasner during the Spring '10 term at University of Texas at Austin.

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lecture12-feb15 - Announcements Lecture 12 Assignment 3 out...

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