Scope. Scope. Region of a program in which a defined object is visible. Defined Objects. Two types of regions. Variables Functions

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Lee Short
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1 Scope & Repetition

2 Scope Scope Region of a program in which a defined object is visible Defined Objects Variables Functions Two types of regions Blocks Not in a block 2 tj

3 Scope Program Prototype Blocks Statements enclosed in { Contents of Main Contents of Functions Not in a Block Global Area // comments #include <stdio.h> int foo; int fun1(int x, int y); // function prototype int main(void){ int x; int y; Main s Area float a; if( ){ float x = a * 3; float a; float b; Nested Block Area else b = x * y; // end of main int fun1 (int i, int j){ int x; int y; // end of fun1 Global Area Function fun1 Area 3 tj

4 Scope Scope An objects scope extends from it s declaration to the end of it s block Global Scope Any object defined in the global area of a program Visible anywhere in the current program Local Scope Any object defined in a block area Includes Main and Functions Visible anywhere in the current block 4 tj

5 Scope Scope Local definitions supersede global definitions within a block // example #include <stdio.h> int x; int y; These x, y are not the same as these int main(void){ int x; float y; 5 tj

6 Scope Scope // comments #include <stdio.h> int foo; int fun1(int x, int y); int main(void){ int x; int y; float a; if( ){ float x = a * 3; float a; float b; else b = x * y; // end of main int fun1 (int i, int j){ int x; int y; // end of fun1 // function prototype foo is visible here this a is visible here but this is a new a 6 tj

7 Scope Scope 7 tj

8 Scope Scope 8 tj

9 Scope Scope 9 tj

10 Scope Scope 10 tj

11 Scope Static Variables Hold their value even after their scope has ended #include<stdio.h> int fun(void); void main(void){ printf("%d ", fun()); printf("%d ", fun()); return; int fun(void){ static int count = 0; count++; return count; 11 tj

12 Repeat a series of instructions - loop How many times Under what conditions Test to determine if we are done Series of instructions 12 tj

13 Loop Testing Test False True Series of instructions Series of instructions True Test Pretest Loop False Post-test Loop 13 tj

14 Loop Testing Eating tacos hungry False True eat taco eat taco True hungry Pretest Loop False Post-test Loop 14 tj

15 Loop Testing Eating tacos hungry False True eat taco eat taco True hungry Pretest Loop False Post-test Loop 15 tj

16 Loop Testing Eating tacos hungry False True eat taco eat taco True hungry Pretest Loop False Post-test Loop 16 tj

17 Loop Initialization Initialize any required loop parameters (variables) Initialization Initialization test False True actions actions True test False Pretest Loop Post-test Loop 17 tj

18 Loop Update Update any required loop parameters (variables) Initialization Initialization test False True actions updates True actions updates test False Pretest Loop Post-test Loop 18 tj

19 Loop Comparison Pretest Post-test Initialization 1 1 # of tests n+1 n Actions executed n n Updates executed n n Min iterations tj

20 Loops in C while pretest loop for pretest loop do while post-test loop 20 tj

21 While loop while(expression) statement; while(expression){ statements; execute statements while expression is true 21 tj

22 While loop Forever while(true) statement while(1){ statements 22 tj

23 While loop - forever Thermostat always running while(1){ temp = get_temp(); setting = get_setting(); if (temp > setting){ heater_off(); ac_on(); else{ heater_on(); ac_off(); Initialization test True actions updates False 23 tj

24 While loop - conditional Factorial num! Full Loop int fact(int num){ int fact; fact = 1; while(num > 0){ fact = fact * num; num--; return fact; 24 tj

25 While loop - conditional Copy pin 3 input to pin 4 as output when pin 5 is high pin 3 -> P3_2, pin 4 -> P3_3, pin 5 -> P4_1 /* * repetition1_msp.c * * Created on: Feb 17, 2017 * Author: Tim */ // copies input pin to output pin when 3rd pin is high // Includes #include "msp432.h" // Global variables // Function prototypes int main(void){ //setbuf(stdout, NULL); // disable buffering // Hardware setup // note: pin 3 is Port 3 bit 2 // note: pin 4 is Port 3 bit 3 // note: pin 5 is Port 4 bit 1 P3->DIR &= ~0x04; // set pin 3 to input P3->DIR = 0x08; // set pin 4 to output P4->DIR &= ~0x02; // set pin 5 to input P3->REN &= 0x0C; // disable pull u/d P4->REN &= ~0x0C; // Local variables // // copy pin 3 in to pin 4 out // when pin 5 is high // while(1){ while((p4->in & 0x02)!= 0){ if(p3->in & 0x04){ P3->OUT = 0x08; else{ P3->OUT &= ~0x08; // end if // end while // end while return 0; // only copy if Pin5 high 25 tj

26 While loop - conditional Copy pin 3 input to pin 4 as output when pin 5 is high pin 3 -> P3_2, pin 4 -> P3_3, pin 5 -> P4_1 /* * repetition1_msp.c * * Created on: Feb 17, 2017 * Author: Tim */ // copies input pin to output pin when 3rd pin is high // Includes #include "msp432.h" // Global variables // Function prototypes int main(void){ //setbuf(stdout, NULL); // disable buffering // Hardware setup // note: pin 3 is Port 3 bit 2 // note: pin 4 is Port 3 bit 3 // note: pin 5 is Port 4 bit 1 P3->DIR &= ~0x04; // set pin 3 to input P3->DIR = 0x08; // set pin 4 to output P4->DIR &= ~0x02; // set pin 5 to input P3->REN &= 0x0C; // disable pull u/d P4->REN &= ~0x0C; // Local variables // // copy pin 3 in to pin 4 out // when pin 5 is high // while(1){ while((p4->in & 0x02)!= 0){ if(p3->in & 0x04){ P3->OUT = 0x08; else{ P3->OUT &= ~0x08; // end if // end while // end while return 0; // only copy if Pin5 high 26 tj

27 For loop for(exp1; exp2; exp3) statement; exp1 -> initialization exp2 -> test exp3 -> update Typically used in counter controlled loops 27 tj

28 For loop Factorial num! int fact(int num){ int fact; fact = 1; int i; for(i = 1; i <= num; i++){ fact = fact * i; return fact; 28 tj

29 For loop Factorial num! int fact(int num){ int fact; fact = 1; int i; for(i = 1; i <= num; i++){ fact = fact * i; return fact; no semi-colon side effect (++) occurs after the statement is evaluated at the end of the for loop 29 tj

30 For loop Factorial num! int fact(int num){ int i; int fact; for(i = 1, fact = 1; i <= num; i++){ fact = fact * i; return fact; comma separated expressions multi-part initializations 30 tj

31 For loop Factorial num! int fact(int num){ int fact; fact = 1; for(int i = 1; i <= num; i++){ fact = fact * i; return fact; declaration included in initialization 31 tj

32 For loop Flash an LED tied to pin 3, starting at 1 flash, up to N flashes N=5 -> ^ _^^_^^^_^^^^_^^^^^_^_^^ /* * repetition2_msp.c * * Created on: Feb 17, 2017 * Author: Tim */ // flash an LED an increasing number of times // Includes #include "msp432.h" // Global variables // Function prototypes void flash(int n); int main(void){ // note: pin 3 is Port 3 bit 2 P3->DIR = 0x04; // set pin 3 to output P3->OUT &= ~0x04; // initialize to off // Local variables // // Increment count and then call flash // while(1){ int count; count = 5; // for testing flash(count); // end while return 0; // end main // Functions // void flash(int n){ int i; int j; for(i=1; i<=n; i++){ for(j=1; j<=i; j++){ P3->OUT = 0x04; _delay_cycles( ); P3->OUT &= ~0x04; _delay_cycles( ); // end for _delay_cycles( * 4); // end for return; 32 tj

33 For loop Flash an LED tied to pin 3, starting at 1 flash, up to N flashes N=5 -> ^ _^^_^^^_^^^^_^^^^^_^_^^ /* * repetition2_msp.c * * Created on: Feb 17, 2017 * Author: Tim */ // flash an LED an increasing number of times // Includes #include "msp432.h" // Global variables // Function prototypes void flash(int n); int main(void){ // note: pin 3 is Port 3 bit 2 P3->DIR = 0x04; // set pin 3 to output P3->OUT &= ~0x04; // initialize to off // Local variables // // Increment count and then call flash // while(1){ int count; count = 5; // for testing flash(count); // end while return 0; // end main // Functions // void flash(int n){ int i; int j; for(i=1; i<=n; i++){ for(j=1; j<=i; j++){ P3->OUT = 0x04; _delay_cycles( ); P3->OUT &= ~0x04; _delay_cycles( ); // end for _delay_cycles( * 4); // end for return; 33 tj

34 Do-While Loop do statement; while(expression); do{ statements; while(expression); Often used in data validation situations 34 tj

35 Do-While Loop float num; do{ printf( enter a number between 1 and 10 ); scanf( %f, &num); while(num >= 1 && num <=10); 35 tj

36 Do-While Loop float num; do{ printf( enter a number between 1 and 10 ); scanf( %f, &num); while(num <= 10 num >=1); 36 tj

37 Do-While Loop While pin 4 is high, flash LED on pin 3 #include "msp.h" void flash(); int main(void){ // Pins // note: pin 3 is Port 3 bit 2 // note: pin 4 is Port 3 bit 3 P3->SEL0 = P3->SEL1 = 0; P3->DIR = 0x04; // set pin 3 to output P3->DIR &= ~0x08; // set pin 4 to input P3->OUT = 0x08; // initialize pin 4 to pullup P3->REN = 0x08; // enable pin 4 pull up while(1){ do{ flash(); while(p3->in & 0x08); _delay_cycles( ); // end while void flash(){ P3->OUT = 0x04; _delay_cycles( ); P3->OUT &= ~0x04; _delay_cycles( ); return; 37 tj

Scope & Register Access

Scope & Register Access Scope Scope Region of a program in which a defined object is visible Defined Objects Variables Functions Two types of regions Blocks Not in a block 2 tj Scope Program Prototype