Decisions II. Switch Statement. If else allows a 2 way decision Switch allows for n-way decisions

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2 Switch Statement If else allows a 2 way decision Switch allows for n-way decisions switch(variable){ case val1: statement; case val2: statement; case val3: statement; default: statement; variable must be an integral value case val1 false case val2 false case val3 false true true true Case val1 Case val2 Case val3 Default 2 tj

3 Switch Statement Launch Countdown #include <stdio.h> #include <unistd.h> int main(void){ setbuf(stdout, NULL); // disable buffering // Local variables int count_down; // get count_down printf("please enter a positive integer value for count_down: "); scanf("%i", &count_down); // count down switch(count_down){ case 5: printf("5\n"); sleep(1); case 4: printf("4\n"); sleep(1); case 3: printf("3\n"); sleep(1); case 2: printf("2\n"); sleep(1); case 1: printf("1\n"); sleep(1); default: printf("blast off"); return 0; 3 tj

4 Switch Statement Switch with break switch(variable){ case val1: statement; statement; case val1: statement; statement; default: statement; statement; Case 1 Decision Case 2 Default 4 tj

5 Switch Statement Test Grades #include <stdio.h> int main(void){ setbuf(stdout, NULL); // disable buffering // Local variables int score; // get count_down printf("please enter test score: "); scanf("%i", &score); // convert score to grade range// score = score/10; // print grade switch(score){ case 10: case 9: printf("a\n"); case 8: printf("b\n"); case 7: printf("c\n"); case 6: printf("d\n"); default: printf("f\n"); return 0; 5 tj

6 Switch Statement Grade ranges #include <stdio.h> int main(void){ setbuf(stdout, NULL); // disable buffering // Local variables char grade; // get count_down printf("please enter a letter grade: "); scanf("%c", &grade); // print grade range switch(grade){ case 'a': case 'A':{ printf("90-100\n"); case 'b': case 'B':{ printf("80-89\n"); case 'c': case 'C':{ printf("70-79\n"); case 'd': case 'D':{ printf("60-69\n"); case 'f': case 'F':{ printf("0-59\n"); default: { printf("error\n"); return 0; 6 tj

7 { not required Switch Statement must be an integral value Grade ranges #include <stdio.h> int main(void){ setbuf(stdout, NULL); // disable buffering // Local variables char grade; // get count_down printf("please enter a letter grade: "); scanf("%c", &grade); // print grade range switch(grade){ case 'a': case 'A':{ printf("90-100\n"); only way to do an or no such thing as case ( a A ): cannot be an expression always include a default case 'b': case 'B':{ printf("80-89\n"); case 'c': case 'C':{ printf("70-79\n"); case 'd': case 'D':{ printf("60-69\n"); case 'f': case 'F':{ printf("0-59\n"); default: { printf("error\n"); not necessary but good practice return 0; 7 tj

8 else if Actually not a new command Special case of nested if if(expr1){ else if(expr2){ else if(expr3){ else{ if(expr1){ else if(expr2){ else if(expr3){ else{ exprx should be different cases of the same test 8 tj

9 else if grades revisited #include <stdio.h> int main(void){ setbuf(stdout, NULL); // disable buffering // Local variables int score; // get count_down printf("please enter test score: "); scanf("%i", &score); // print grade if(score >= 90) printf("a\n"); else if(score >= 80) printf("b\n"); else if(score >= 70) printf("c\n"); else if(score >= 60) printf("d\n"); else printf("f\n"); return 0; 9 tj

10 else if grades revisited #include <stdio.h> int main(void){ setbuf(stdout, NULL); // disable buffering // Local variables int score; // get count_down printf("please enter test score: "); scanf("%i", &score); Final option is just an else All tests are measures of the same expression // print grade if(score >= 90) printf("a\n"); else if(score >= 80) printf("b\n"); else if(score >= 70) printf("c\n"); else if(score >= 60) printf("d\n"); else printf("f\n"); return 0; 10 tj

11 Turn on LEDs in a pattern p4_0 -> p4_5 = 24,5,25,6,26 // class_switch #include "msp432.h" void setup() { // initialize the LED pins: // note: P4_0 -> P4_4 match to 24,5,25,6,26 P4DIR = 0x1F; // set to outputs P4SEL0 &= ~0x1F; // use as GPIO P4SEL1 &= ~0x1F; void loop() { int count; for(count = 0; count <=5; count ++){ delay(1001); switch (count) { case 0: P4OUT = 0x01; P4OUT &= ~0x1E; case 1: P4OUT = 0x02; P4OUT &= ~0x1D; case 2: P4OUT = 0x04; P4OUT &= ~0x1B; case 3: P4OUT = 0x08; P4OUT &= ~0x17; case 4: P4OUT = 0x10; P4OUT &= ~0x0F; default: P4OUT &= ~0x1F; 11 tj

12 Turn on LEDs in a pattern p4_0 -> p4_5 = 24,5,25,6,26 // class_switch2 #include "msp432.h" void setup() { Serial.begin(9600); // initialize the LED pins: // note: P4_0 -> P4_4 match to 24,5,25,6,26 P4DIR = 0x1F; // set to outputs P4SEL0 &= ~0x1F; // use as GPIO P4SEL1 &= ~0x1F; void loop() { delay(1001); int count; Serial.println("enter number between 0 and 4"); count = Serial.read(); Serial.println(count); switch (count) { case '0': P4OUT = 0x01; P4OUT &= ~0x1E; case '1': P4OUT = 0x02; P4OUT &= ~0x1D; case '2': P4OUT = 0x04; P4OUT &= ~0x1B; case '3': P4OUT = 0x08; P4OUT &= ~0x17; case '4': P4OUT = 0x10; P4OUT &= ~0x0F; default: P4OUT &= ~0x1F; 12 tj