# CPS125

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## CPS125

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1. CPS125 Week 5

3. Nested if … else Very similar to if … else … statement seen before • Example: if (exp_1) stat_1; else if (exp_2) stat_2; else stat_3; Description: • If exp_1 is TRUE then stat_1 • If exp_1 is FLASE and exp_2 is TRUE then stat_2 • If exp_1 is FLASE and exp_2 is FALSE then stat_3

4. Practice!/* PROGRAM #10 */ • /* PROGRAM TO CALCULATE GST AND PST */ • #include <stdio.h> • #include <stdlib.h> • #define GST 0.08 • #define PST 0.05 • main( ){ char choice; float Ptax, Gtax; float BTprice, ATprice; • /* Get the selected letter by user */ • printf("Use the menu - Select a Letter:\n"); • printf("P] Provincial Tax. G] Goods &Services Tax.\n"); • printf("Your selection (P or G): "); • scanf("%c", &choice); • /* Get the price before tax, calculate GST and PST print the result*/ • printf("Please enter the Before the Tax price"); • scanf("%f", &BTprice);

5. PrACTICE! Program: CALCULATE GST AND PST • if (choice == ‘G’){ • ATprice = GST * BTprice; • printf("The Before Tax Price is %f.\n",BTprice); • printf("The After Tax Price is %f.\n”, ATprice); • } else • if (choice == ‘P’){ • ATprice = PST * BTprice; • printf("The Before Tax Price is %f.\n",BTprice); • printf("The After Tax Price is %f.\n”, ATprice); • } else{ • printf("That was not one of the choices.\n"); • printf("Sorry!\n"); • } exit(0); • }

8. Practice!The traffic light program (nested ifs) • A program that displays the recommended actions depending on the color of a traffic light. • This program uses nested if statements.

9. Practice! Traffic light • /* The traffic light program (nested ifs) */ • #include <stdio.h> • int main (void) • { char colour; /* ask user for colour */ • printf ("Enter the colour of the light (R, G or Y): "); • scanf ("%c", &colour); /* test if colour is red */ • if (colour == 'r' || colour == 'R') • printf ("STOP! \n"); • else • if (colour == 'y' || colour == 'Y') /* yellow colour test */ • printf ("CAUTION! \n"); • else if (colour == 'g' || colour == 'G') /* green colour test */ • printf ("GO! \n"); • else /* if not Y or G or R then invalid colour */ • printf ("INVALID COLOUR! \n"); • return (0); • }

10. SWITCH

11. C Switch • C has built in multiple-branch selection statement, called switch, which successively tests the value of an expression against a list of integer or character constants floating point and double are not allowed. • Switch statement is often used to process keyboard commands, such as menu selection. • When a match is found ,the statements associated with that constant are executed. The value of expression is tested against the values, one after another, of the constants specified in the case statements. • When a match is found, the statement sequence associated with that case is executed, until the break statement or the end of the switch statement is reached. • The default statement is executed if no matches are found. The default is optional, and if it is not present, no action takes place if all matches fail.

12. C Switch To make selection out of several choices Very Similar to if … else … But probably easier way to code multiple if … else … switch (selection){ case choice1 : (statement1); break; … … … default : (statementN); }switch, case, break, default: ‘C’ reserved wordsselection: A ‘C’ expression, can be either int or char. choice: required match, must be of same type as expression1.

13. Switch Statement • The switch statement is a useful alternative for multiple branches (not just true and false). • It works not with conditions but with control values. • The control values must be int or char only, never double. • The control values must be discrete, never ranges.

14. NOTE!!! • If SELECTION matches any of the CHOICES, then the corresponding statement will be executed. • DEFAULT is used when no match is made, then this option will be executed. • BREAK is used to get out of terminate the SWITCH statement. • Nested switch statements can be used if required.

15. /* PROGRAM # 12 */ • /* PROGRAM #12 */ /* USE OF IF STATEMENT FOR A MENU SYSTEM */ • #include <stdio.h> • #define TGPA 4.3 • #define CGPA 3.00 • #define CPS125 'A’ • main (){ int choice; /*Get the user's selected option*/ • printf("Select one of the following choice:\n"); • printf("1)TGPA , 2)CGPA, 3)CPS125\n"); scanf("%d",&choice); /* Print the result based on the input */ • if (choice == 1) • printf("Your term GPA is: %3.2f.\n",TGPA); • else • if (choice == 2) • printf("Your Cumulative GPA is: %3.2f.\n",CGPA); • else • if (choice == 3) • printf("Your grade in CPS125 is: %c. ",CPS125); • else • printf("The selected option does not exist!"); }

16. PRACTICE! /* PROGRAM # 13 */ • /* PROGRAM #13 */ /* USE OF SWITCH STATEMENT */ • #include <stdio.h> • #define TGPA 4.3 • #define CGPA 3.00 • #define CPS125 'A' • main (){ int choice; • /*Get the user's selected option*/ • printf("Select one of the following choice:\n"); • printf("1)TGPA , 2)CGPA, 3)CPS125\n"); • scanf("%d",&choice); • /* Using switch statement to print the result based on the input */ • switch (choice ){ case 1: printf("Your term GPA is: %3.2f.\n",TGPA); • break; • case 2: printf("Your Cumulative GPA is: %3.2f.\n",CGPA); • break; • case 3: printf("Your grade in CPS125 is: %c. ",CPS125); • break; • default: printf("The selected option does not exist!"); } }

17. PRACTICE! /* PROGRAM # 14 */ • /* USE OF IF_ELSE STATEMENT AND SWITCH *//* This program is not complete yet but at this point we don’t know enough to fix it*/ • #include <stdio.h> • main( ){ char choice; • float course1=0, course2=0, course3=0; • float sum=0, TGPA; /* Make a selection from the menu */ • printf("Select one of the following choice:\n"); • printf("a)Get the grades for 3 courses, \n”); • printf("b)Calculate the term GPA [CGPA],\n"); • printf("c)Print course and GPA information,\n"); • scanf("%c", &choice); • /* Should work for upper case & lower case */ • if ( choice == ‘a’ || choice == ‘A’) • choice= ‘a’; • if ( choice == ‘b’ || choice == ‘B’) • choice= ‘b’; • if ( choice == ‘c’ || choice == ‘C’) • choice= ‘c’;

18. switch(choice){ • case ‘a’:{ printf("Pls enter the grade for the 1st course: "); • scanf("%f",&course1); • printf("Pls enter the grade for the 2nd course: "); • scanf("%f",&course2); • printf("Pls enter the grade for the 3rd course: "); • scanf("%f",&course3); } break; • case ‘b’:{ if (course1 == 0 && course2 == 0 && course3== 0 ){ • printf(“You need to provide the grades first and then try to calculate the GPA.\n”); • } else{ sum=course1+course2+course3; • TGPA=sum/3.0; } • } break; • case 'c':{ if (TGPA == 0 ){ • printf(“Need to provide the grades first & then calculate the GPA, & try this option.\n”); • } else{ printf(“Course#1: %f\n”, course1); printf(“Course#2: %f\n”, course2); • printf(“Course#3: %f\n”, course3); printf(“Your term GPA is: %f\n”, TGPA); }} break; default: printf("Sorry wrong selection! Pls try again!\n"); }}

19. Important EXTRA Practice!

20. Expressions • -Identify variables • You could have A+-Z%B if they are non zero and integer. • You could not have the expression :ab-cd+3bx • After each operation we must have an operand: x+xy-z • Look at the ( )well. A+(b+c)-(a-d) • Do not use reserved words: void ,char. • You could use soft rules: A standard identifier is a name used by C but is not a reserved word. printf, scanf are examples of standard identifiers. • Be careful we must use functions in C for math .

21. Expressions • -x- y*z……..-x then y*z then –x-result of the second step. • (x<y || x<z) && x>0.0 …first && • You can also use parentheses to clarify the meaning of the expression. • If x,min,max are type double ,the C compiler interprets the expression • x+y<min+max correctly as: (x+y)<(min+max)

22. Character Comparisons